Space Articles



1. Where Does The Earth's Gold Come From?
2. Robots In Space
3. UFO's - From Earth
4. Mining Asteroids
5. Why Is The Sun So Round?
6. The Pioneer Anomaly
7. Mining Asteroids 2
8. Who Owns Them?
9. Inflatable Space Stations
10. Space Elevator For The Moon
11. 80 Million Apollo Meteorites
12. An Unusual Asteroid
13. Pluto
14. Space Elevators Feasibilty
15. Meteorites
16. Eye Problems In Space
17. How Likely Is Life On Other Worlds?








Where Does All Earth's Gold Come From? Precious Metals the Result of Meteorite Bombardment

  • ScienceDaily (Sep. 9, 2011) — Ultra high precision analyses of some of the oldest rock samples on Earth by researchers at the University of Bristol provides clear evidence that the planet's accessible reserves of precious metals are the result of a bombardment of meteorites more than 200 million years after Earth was formed.

    During the formation of Earth, molten iron sank to its centre to make the core. This took with it the vast majority of the planet's precious metals -- such as gold and platinum. In fact, there are enough precious metals in the core to cover the entire surface of Earth with a four-metre thick layer.

    The removal of gold to the core should leave the outer portion of Earth bereft of bling. However, precious metals are tens to thousands of times more abundant in Earth's silicate mantle than anticipated. It has previously been argued that this serendipitous over-abundance results from a cataclysmic meteorite shower that hit Earth after the core formed. The full load of meteorite gold was thus added to the mantle alone and not lost to the deep interior.

    To test this theory, Dr Matthias Willbold and Professor Tim Elliott of the Bristol Isotope Group in the School of Earth Sciences analysed rocks from Greenland that are nearly four billion years old, collected by Professor Stephen Moorbath of the University of Oxford. These ancient rocks provide a unique window into the composition of our planet shortly after the formation of the core but before the proposed meteorite bombardment.

    The researchers determined the tungsten isotopic composition of these rocks. Tungsten (W) is a very rare element (one gram of rock contains only about one ten-millionth of a gram of tungsten) and, like gold and other precious elements, it should have entered the core when it formed. Like most elements, tungsten is composed of several isotopes, atoms with the same chemical characteristics but slightly different masses. Isotopes provide robust fingerprints of the origin of material and the addition of meteorites to Earth would leave a diagnostic mark on its W isotope composition.

    Dr Willbold observed a 15 parts per million decrease in the relative abundance of the isotope 182W between the Greenland and modern day rocks. This small but significant change is in excellent agreement with that required to explain the excess of accessible gold on Earth as the fortunate by-product of meteorite bombardment. Dr Willbold said: "Extracting tungsten from the rock samples and analysing its isotopic composition to the precision required was extremely demanding given the small amount of tungsten available in rocks. In fact, we are the first laboratory world-wide that has successfully made such high-quality measurements."

    The impacting meteorites were stirred into Earth's mantle by gigantic convection processes. A tantalising target for future work is to study how long this process took. Subsequently, geological processes formed the continents and concentrated the precious metals (and tungsten) in ore deposits which are mined today.

    Dr Willbold continued: "Our work shows that most of the precious metals on which our economies and many key industrial processes are based have been added to our planet by lucky coincidence when the Earth was hit by about 20 billion billion tonnes of asteroidal material."

Robots In Space

    While human explorers remain stubbornly stuck in Earth orbit, robotic space probes are preparing for the next great age of exploration: drilling, rolling, sailing, and prospecting where nobody has gone before.

    The robots are out there, dozens of them, going where their soft-bodied, oxygen-breathing creators can’t or won’t anytime soon. They own space. While a handful of humans hunker down in near-Earth orbit in the International Space Station, an aging craft conceived in the Reagan era, unmanned machines at this very moment are orbiting Mercury, trundling across the sands of Mars, even preparing to leave the confines of the solar system.

    The space station is a thing of beauty in its way, the apotheosis of Apollo-style technology. But in terms of scientific achievements it suffers in comparison with NASA’s spaceborne fleet of robots—currently 55 strong—especially given the large funding gap that has always existed between the manned and unmanned space programs. NASA’s budget for 2012 provides about $4.5 billion for robotic space science, versus $8.3 billion for human space exploration, almost $3 billion of which goes to the station alone. And that is the outlay for a NASA without shuttle flights or plans to send people back to the moon.

    Noble as human exploration may be, we would know very little about anything in the cosmos much more distant than the moon were it not for robotic explorers. Through them we have learned of lava plains on Venus, a buried ocean on Jupiter’s moon Europa, lakes of methane on Saturn’s moon Titan, and salty geysers on another Saturnian moon, Enceladus. And manned missions? Since the Apollo moon landing of 1969, NASA has mostly confirmed what it knew from the outset, which is that hurtling humans deep into space is expensive, dangerous and, for the foreseeable future, beyond reach. The reality is, when it comes to carrying out serious space science, humans simply can’t compete with spacefaring hardware. And that is probably not going to happen in our lifetime.

    Sheltered as we are by Earth’s atmosphere and magnetic field, which deflect lethal radiation from space, we are like coddled children who have never ventured into a tough neighborhood. The space station, orbiting less than 250 miles overhead (about the distance between Boston and Philadelphia) hardly qualifies as a space station at all. It is really more of a not-quite-above-Earth’s-atmosphere station, since it, like the shuttles once did, travels within the thin air of the ionosphere.

    Real outer space is hazardous, even for robots. Ed Stone, the project scientist for the astonishingly successful twin Voyager missions that flew past Jupiter, Saturn, Uranus, and Neptune in the late 1970s and 1980s, and are now on their way to the stars, says the Voyagers would not have survived their close encounters with Jupiter had it not been for some advance warning from a previous mission.

    That precursor mission, called Pioneer 10, flew past Jupiter in 1973. It did not get as close to Jupiter as the two Voyagers would, but it got near enough to find that the massive planet could wreak havoc on spacecraft. "Pioneer 10 discovered that the radiation environment of Jupiter was much more severe than anyone had expected," Stone says. "It took us nine months to redo the circuitry on the Voyager spacecraft to make it much less susceptible to radiation effects."

    In just a few hours near Jupiter, Voyagers 1 and 2 absorbed blasts of radiation hundreds of times greater than the lethal dose for humans. And surface conditions on some planets are even more murderous. The early Soviet Venera probes, the first spacecraft to touch down intact on another world, were built like tanks. Even so, they succumbed to Venus’s crushing atmospheric pressure and 900 degree Fahrenheit surface temperatures—hot enough to melt lead—within a couple hours of landing.

    The sheer harshness of the environment that begins a few hundred miles above our heads, and the huge distances involved in traveling to other planets, bode poorly for any of us who might dream of establishing human outposts much beyond Mars. "I don't think the stories of science fiction we read in childhood are ever going to happen," says John Mather, a Nobel laureate who is now the senior project scientist for the James Webb Space Telescope, the $6.5 billion successor to the Hubble telescope that NASA plans to launch in 2018. "People won't be rocketing around the solar system. I think we'll be able to send people throughout the inner solar system, to visit asteroids, comets, and Mars - if we want to. Beyond that," he says, pausing for a moment, "people are fragile, and we cry when they die. Robots are fragile but we don’t cry when they die."

    Perhaps the demise of some robots should be mourned. Right now, the two Voyager spacecraft are poised at the very edge of the solar system; Voyager 2, the more distant, is nearly 11 billion miles from Earth. The spacecraft have traveled farther than any other objects humanity has made, and they are still sending back data 34 years after their launch. Both Voyagers have reached the outer limits of the heliosphere, an enormous, tenuous bubble of charged particles from the sun that surrounds our solar system.

    Instead of the relatively stable environment that was expected at the brink of interstellar space, the Voyagers have encountered what some scientists have described as a 'magnetic jacuzzi,' a region where the sun’s magnetic field appears to be ripping apart and reconnecting, forming bubbles millions of miles across. It is a place human explorers will not visit in the foreseeable future, although the data on the flux of cosmic rays (energetic particles from deep space) into the solar system will allow engineers to better gauge the risk to both spacecraft and humans during extended space voyages. The Voyagers are now so far away that the signals from their 23-watt radio transmitters, powered by a radioactive generator, take more than 12 hours to reach Earth. Sometime within the next five years Voyager 1 will become the first spacecraft to cross the boundary of the heliosphere and enter interstellar space. There it is likely to be buffeted by winds of particles from supernovas that will be colder and denser than the solar wind, though still not as dangerous as Jupiter’s radiation belts. The spacecraft should have several years to explore the new realm. "We have enough electrical power to operate fully until 2020," says Stone, who has been involved with the Voyagers since their inception.

    In the meantime, NASA is planning some 30 new robotic missions to explore cosmic mysteries closer to home. The billion-dollar Solar Probe Plus, tentatively slotted for launch in 2018, would skim the outer atmosphere—or corona—of the sun itself, repeatedly dipping within five solar diameters of the sun’s surface, far closer than any probe has ever approached our star. The spacecraft’s exterior will endure 2600 degree Fahrenheit temperatures, while keeping the craft’s payload at room temperature. “It will work its way in over a period of seven years, getting closer and closer,” says Paul Hertz, chief scientist at NASA’s Scientific Mission Directorate. “Our goal is to find out how the solar wind gets accelerated, and why the corona is even hotter than the surface of the sun.” NASA’s biggest ambition is the hunt for life and a habitat that can support it. Several planned or proposed missions will specifically explore the question of whether life exists, or once existed, elsewhere in our solar system. In late November, NASA plans to launch a 10-foot-long, six-wheel-drive mobile robot named Curiosity. If all goes well, the $2 billion bot will land on Mars nine months later and begin looking for signs of past or present life in rock and soil samples, all the while immune to the toxic dust, freezing temperatures, and space radiation that would derail human geologists.

    Unencumbered by human frailties, Curiosity—like the rovers Spirit and Opportunity, which survived on the Red Planet years longer than expected—will be free to hunt for E.T. "If we find evidence for life on Mars, boy, are we just gonna go wild with speculation about how common it is in the universe," says Lou Friedman, a former scientist with NASA’s Jet Propulsion Laboratory in Pasadena and cofounder, with Carl Sagan, of the Planetary Society. "Because here we are within a hundred years of the start of the space age and we find life on another world. Wow! That’s one way of looking at it. Another way is, here we are in the solar system with all its variations in planetary environments, and if we don’t find life, that’s going to be a downer."

    What comes after the Mars Science Lab is uncertain. Last March the National Research Council released a 400-page report called the Planetary Decadal Survey, which recommended 25 possible missions for NASA between 2013 and 2022. At the top of the list was the Mars Astrobiology Explorer Cacher, or MAX-C, which would collect soil and rock samples for a later mission that would return them to Earth. Perhaps by then manned missions will have resumed, and NASA might even have at last a solid plan for sending humans to Mars too.

    For now, the second-highest priority mission on NASA’s wish list is the Jupiter Europa Orbiter, which would survey the ice-covered moon Europa and the global ocean that seems to lie beneath its frozen surface. If life exists anywhere else in the solar system, it may be in Europa’s ocean, which is estimated to be about 60 miles deep, its waters kept above freezing by the moon’s gravitational interactions with Jupiter.

    “We know very little about that ocean,” says Steven Squyres, an astronomer at Cornell University who has been involved with many robotic missions. "We don't know how thick the ice is, where the thin spots are, or where on the surface you might go to find out what it's like inside Europa. So the orbiter mission is designed to address some of those questions."

    It now seems likely that mundane terrestrial concerns—the federal budget deficit - will force NASA to postpone the Europa mission indefinitely. "We apparently won't be doing a Jupiter Europa Orbiter anytime soon," Hertz says. "That's a mission I wish we could do. It would be a great one. But with this budget we have to prioritize. Everything we do is great, and some of the things we don’t do would be great too."

    One of the most intriguing of NASA's possible future missions would involve a visit to Titan, Saturn’s largest moon. The Titan Mare Explorer would be the first mission to explore an extraterrestrial sea, dropping a capsule onto Ligeia Mare, one of Titan’s seas of liquid methane, in 2023. The capsule, built to withstand the –300 degree Fahrenheit temperatures, would float on that oil-black sea for up to three months, looking for organic chemicals that might be similar to the ones that allowed life to begin on Earth.

    It is likely that in another decade or two the achievement gap between human and robotic space exploration will have widened only further. By then, robots may even have found evidence for life on Mars or on one of the moons of Jupiter or Saturn. So where does that leave us? Are we destined forever to experience the solar system vicariously through robotic eyes?

    "I don’t think we're at the stage of human evolution where we should give up on going out there," Lou Friedman says. "To me, there’s a deep and profound connection between unmanned and human exploration. They drive each other. Robotic exploration drives our interest in doing follow-up missions with humans. It may be that in the future we will stay hidebound and let robots explore the universe. But I'm not there yet. I'm a human chauvinist, and I’m rooting for the humans."

    We will follow the robots one day. With heavily shielded spaceships, perhaps we will brave Jupiter's deadly radiation belts. Maybe we will get to see the moon Io, a hellish world of nonstop sulfur volcanoes, against a backdrop of Jupiter’s enormous colored bands of clouds. But one thing is certain. Wherever we go, whether we are gazing at geysers on Enceladus or tramping the sands of Mars, robots will have been there first.

UFO's - From Earth

    The asteroid that killed the dinosaurs 65 million years ago (10 km in diameter, mass greater than 1 trillion tons) must have ejected billions of tons of life-bearing meteorites into space. Now Kyoto Sangyo University physicists have calculated this could have seeded life in the solar system and even as far as Gliese 581, Technology Review Physics arXiv Blog reports.

    Their results contain a number of surprises:

    As much ejecta would have ended up on Europa as on the Moon: around 100 million individual Earth rocks in some scenarios. That’s because the huge gravitational field around Jupiter acts as a sink for rocks, which then get swept up by the Jovian moons as they orbit.

    A previous study found that more Earth ejecta must end up in interstellar space than all the other planets combined.

    About a thousand Earth-rocks from this event would have made its way to Gliese 581 (a red dwarf some 20 light years from here that is thought to have a super-Earth orbiting at the edge of the habitable zone), taking about a million years to reach their destination. Life-bearing ejecta from Earth would take a trillion years for ejecta to spread through a volume of space the size of the Milky Way.

    If life evolved at just 25 different sites in the galaxy 10 billion years ago, the combined ejecta from these places would now fill the Milky Way.

    The probability is almost 1 (close to certain) that our solar system is visited by microorganisms that originated outside our solar system.

Mining Asteroids?

    CAN reality trump art? That was the question hovering over the launch on April 24th, at the Museum of Flight in Seattle, of a plan by a firm called Planetary Resources to mine metals from asteroids and bring them back to Earth.

    It sounds like the plot of a film by James Cameron—and, appropriately, Mr Cameron is indeed one of the company's backers. The team behind the firm, however, claim they are not joking. The company's founders are Peter Diamandis, instigator of the X Prize, awarded in 2004 to Paul Allen and Burt Rutan for the first private space flight, and Eric Anderson, another of whose companies, Space Adventures, has already shot seven tourists into orbit. Larry Page and Eric Schmidt, respectively the chief executive and the chairman of Google, are also involved. So, too, is Charles Symonyi, the engineer who oversaw the creation of Microsoft's Office software (and who has been into space twice courtesy of Mr Anderson's firm). With a cast-list like that, it is at least polite to take them seriously.

    As pies in the sky go, some asteroids do look pretty tasty. A lot are unconsolidated piles of rubble left over from the beginning of the solar system. Many, though, are pieces of small planets that bashed into each other over the past few billion years. These, in particular, will be high on Planetary Resources' shopping list because the planet-forming processes of mineral-melting and subsequent stratification into core, mantle and crust will have sorted their contents in ways that can concentrate valuable materials into exploitable ores. On Earth, for example, platinum and its allied elements, though rare at the surface, are reckoned more common in the planet's metal-rich core. The same was probably true of the planets shattered to make asteroids. Indeed, the discovery of a layer of iridium-rich rock (iridium being one of platinum's relatives) was the first sign geologists found of the asteroid impact that is believed to have killed the dinosaurs.

    Most asteroids dwell between the orbits of Mars and Jupiter. But enough of them, known as near-Earth asteroids, or NEAs, come within interplanetary spitting distance of humanity for it to be worth investigating them as sources of minerals—if, of course, that can be done economically.

    First catch your hare

    The first thing is to locate a likely prospect. At the moment, about 9,000 NEAs are known, most of them courtesy of ground-based programmes looking for bodies that might one day hit Earth. That catalogue is a good start, but Planetary Resources plans to go further. In 2014 it intends to launch, at a cost of a few million dollars, a set of small space telescopes whose purpose will be to seek out asteroids which are easy to get to and whose orbits return them to the vicinity of Earth often enough for the accumulated spoils of a mining operation to be downloaded at frequent intervals.

    That bit should not be too difficult. But the next phase will be tougher. In just over a decade, when a set of suitable targets has been identified, the firm plans to send a second wave of spacecraft out to take a closer look at what has been found. This is a significantly bigger challenge than getting a few telescopes into orbit. It is still, though, conceivable using existing technology. It is after this that the handwaving really starts.

    Broadly, there are two ways to get the goodies back to Earth. The first is to attempt to mine a large NEA in its existing orbit, dropping off a payload every time it passes by. That is the reason for the search for asteroids with appropriate orbits. This approach will, however, require intelligent robots which can work by themselves for years, digging and processing the desirable material. The other way of doing things is for the company to retrieve smaller asteroids, put them into orbit around Earth or the moon, and then dissect them at its leisure. But that limits the value of the haul and risks a catastrophic impact if something goes wrong while the asteroid is being manoeuvred.

    Either way, the expense involved promises to be out of this world. A recent feasibility study for the Keck Institute for Space Studies reckoned that the retrieval of a single 500-tonne asteroid to the moon would cost more than $2.5 billion. Earlier research suggested that, to have any chance of success, an asteroid-mining venture would need to be capitalised to the tune of $100 billion. Moreover, a host of new technologies will be required, including more-powerful solar panels, electric-ion engines, extraterrestrial mining equipment and robotic refineries.

    All of which can, no doubt, be done if enough money and ingenuity are applied to the project. But the real doubt over this sort of enterprise is not the supply, but the demand. Platinum, iridium and the rest are expensive precisely because they are rare. Make them common, by digging them out of the heart of a shattered planet, and they will become cheap. The most important members of the team, then, may not be the entrepreneurs and venture capitalists who put up the drive and the money, nor the engineers who build the hardware that makes it all possible, but the economists who try to work out the effect on the price of platinum when a mountain of the stuff arrives from outer space.

Why Is The Sun So Round?

    A new study has been published that seems very simple yet has some very interesting repercussions: it shows the Sun is the most spherical natural object ever measured. Measuring the Sun’s diameter is actually rather difficult. For one thing, observations from the ground have to deal with our atmosphere which warbles and waves above us, distorting images of astronomical objects. To get past that, the researchers used a camera on NASA’s Solar Dynamics Observatory, which orbits high above the Earth. The camera is very stable, and gets past a lot of the problems of measurement uncertainty.

    Another problem is that the Sun doesn’t have a solid surface. It’s not like a planet – and even that can be tough to measure. Since the Sun is gaseous, it just kind of fades away with height, so if you try to get too precise you find a lot of wiggle room in the size. In fact, the largest variation the researchers found in the solar diameter was due to intrinsic roughness of the Sun’s limb – in other words, on very small scales the Sun isn’t smooth.

    Still, there are ways around that. The point here isn’t necessarily to find the actual size, but the ratio of the diameter of the Sun through the poles (up and down, if you like) to the diameter through the equator. That tells you how spherical the Sun is.

    What I would expect is that the Sun is slightly larger through the equator than through the poles, because it spins. That creates a centrifugal force, which is 0 at the poles and maximized at the equator. Most planets are slightly squished due to this, with Saturn – the least dense and fastest spinning planet, with a day just over 10 hours long – having a pole to equator ratio of about 90%. It’s noticeably flattened, even looking through a relatively small telescope. The Sun spins much more slowly, about once a month. That means the centrifugal force at its equator isn’t much, but it should be enough to measure. So the scientists went and measured it. And what they found is that the polar and equatorial diameters are almost exactly the same. In fact, they found that the equatorial diameter is 5 milliarcseconds wider than the polar diameter. An arcsecond is a measure of the size of an object on the sky (1° = 60 arcminutes = 3600 arcseconds), and the Sun is about 30 arcminutes (1800 arcseconds) across. In other words the equatorial diameter is only 0.0003% wider than the polar diameter!

    The Sun is a 99.9997% perfect sphere. Hmmm.

    Put another way, if you shrank the Sun to the size of a basketball, the equatorial diameter would be wider than the polar one by about 0.4 microns – the width of a human hair less than the size of an average bacterium! That’s actually pretty cool.

    What this almost certainly means is that the assumptions people make about the Sun aren’t quite on the ball*. One assumption is that the Sun is a big ball of gas, and the only forces on it are gravity, pressure, and centrifugal force. The physics of those aren’t too hard to work out, but up until now predict a slightly squashed Sun. So something else must be going on.

    One obvious thing is the Sun’s ridiculously complicated magnetic field. The gas inside the Sun is hot, and the atoms making it up have their electrons stripped off. That makes them ions (and the gas is then called a plasma), which are affected by magnetic fields. It’s possible that the strength of the magnetism inside the Sun acts like a sort of tension, stiffening the Sun, so it doesn’t bulge out at the equator as much as expected (or at all).

    Also, since the Sun isn’t solid, it doesn’t spin as one. Parts of it rotate faster than other parts; it spins once every 25 days at the equator, but every 35 days at the poles. It’s possible that this isn’t constant with depth (plasma under the surface may spin at different rates than stuff at the surface) and that could affect this as well.

    Most interestingly to me is that the scientists determined the Sun’s size doesn’t change with time, including the 11 year solar cycle. The Sun’s overall magnetic field fluctuates with time, weakening and strengthening on an 11 year cycle (which is why we’re seeing more sunspots now; we’re approaching solar max). If the Sun’s shape were being restricted by interior magnetic fields, you might expect the size to change slightly with the cycle as well. The scientists who did this study have ruled that out.

    So what’s going on? Hard to say. We do actually have a very good understanding of the solar interior due to advances in physics over the past century or so – models have been tested very carefully and what we have now works extremely well… up to a point. What will happen next is that different models will be tested to see which ones can match observations, then more predictions will be made, and then more and better observations will be done to test those predictions. Some models will survive this trial, and our understanding will have grown. This issue of the Sun’s sphericity strikes me as a fluctuation on what we know. It doesn’t mean everything we thought we knew is wrong, just that there’s more to know about the Sun.

    And that, of course, is why science is so much fun! It never ends, and there’s always something new and interesting to discover.


The Pioneer Anomaly

    Astrophysicist Slava Turyshev has explained away decades of exotic speculation over the Pioneer anomaly, the puzzling slowdown of two NASA probes.

    What drew you to try to explain the anomaly, the unexpected slowing of the Pioneer 10 and 11 spacecraft that emerged in the 1980s?

    The whole solar system is a lab which I use to test general relativity. We know the solar system obeys all laws given to us by Einstein and Newton. With the Pioneer anomaly, suddenly we saw a very unusual tiny force that fell right in between Newton's gravity and Einstein's general relativity. That prompted people to think that maybe the spacecraft was sensing the presence of a new type of physics. It was either a major discovery or a puzzle that, in the solving, would help us build better craft to study gravity. It was a win-win situation for me.

    What were the initial thoughts on a cause?

    Engineers thought it was due to expected leakage from the propellant system, just as water still drips from a hose after you've turned off the tap. But then we saw this same small pushing motion for months and years, even when we didn't use the propulsion system, so people started to think maybe something else was going on.

    You meticulously modelled Pioneer 10 using design and flight data to test a mundane cause of the anomaly. Tell me about that.

    Before our latest work, there was some expectation we would see part of the anomaly was due to the spacecraft's thermoelectric generators producing a lot of heat. This heat recoils and gives a minuscule push against the craft. We didn't know that this push would match the profile of the anomaly, but that is just what we found in our latest work.

    Is this is the final word on it?

    We still have an uncertainty in our study of less than 18 per cent. But for me, this is the answer. Some may argue it is not final, but in my mind we did a good job and it's very clear what happened.

    Why has it taken so long to reach this point?

    Lack of proper data storage was a huge problem. In the 1970s and '80s, mission data was recorded on magnetic tapes, and to study the Pioneer anomaly we needed the probe's navigational data. But mission tapes were normally saved for only a few months and then thrown away, so you're lucky if you can find what you need. The only data available from Pioneer 10 was from planetary flybys, which were kept to study gravity around planets. Then we had to figure out how to read it. You need a proper machine with the right software, and you need to "upconvert" the data to modern formats so it can be used in today's computer modelling systems. That took years.

    Any more cosmic conundrums in your sights?

    I'd like to see more work on the search for gravitational waves, which are ripples in the fabric of space-time predicted to exist by general relativity. They open up a completely different way of looking at the universe, because these waves would allow us to detect phenomena beyond what we can see with light. What's past the event horizons of black holes? Are there other universes? Do wormholes exist?


Asteroid Mining

    Not content with sending the first tourist into space and landing NASA's Mars rovers between them, Eric Anderson and Chris Lewicki have an outlandish plan to mine asteroids, backed by Google billionaires. But, they tell Paul Marks, that's just the start.

    Your asteroid mining company Planetary Resources is backed by the Google executives Larry Page and Eric Schmidt. How tough was it to convince them to invest?

    Eric Anderson: The Google guys all like space and see the importance of developing an off-planet economy. So Larry Page and Eric Schmidt became investors. And Google's Sergey Brin has his name down as a future customer of my space tourism company Space Adventures.

    You want to put space telescopes in orbit to seek out asteroids rich in precious metals or water - and then send out robotic spacecraft to study and mine them. Are you serious? Chris Lewicki: Yes. We're launching the first telescopes in 18 months - and we're actually building them ourselves in our own facility in Bellevue, Washington. We have a team of more than 30 engineers with long experience of doing this kind of thing at NASA's Jet Propulsion Laboratory, myself included. Many of our team worked on designing and building NASA's Curiosity rover, and I was a system engineer on the Spirit and Opportunity rovers - and flight director when we landed them on Mars.

    How many asteroid-spotting telescopes will you need - and are they anything like Hubble? EA: We'd like to put up at least 10 or 15 of them in orbit in the next five years, some of them on Virgin Galactic rockets. They're a lot less capable than Hubble, which is a billion dollar space vehicle the size of a school bus. Our telescopes - which we call the Arkyd 100 spacecraft - are cubes half-a-metre on a side and will cost around $1 million each, though the first one, of course, will cost much more. But when they are developed to a high level of performance, we want to print them en masse on an assembly line. They will have sub-arc-second resolution, which is just a mind-blowing imaging capability.

    CL: The smaller we can make them the lower they cost to launch. Making them the size of a mini fridge, with 22-centimetre-diameter optics, hits the sweet spot between capability and launch cost.

    How can you tell if an asteroid might have platinum, gold or water deposits? CL: We'll characterise them by studying their albedo - the amount of light that comes from them - and then with the appropriate instruments we can start to classify them, as to what type of asteroid they are, whether they are stony, metallic or carbonaceous. We're starting with optical analyses though we could use swarms of Arkyd 100s with spectroscopic, infrared or ultraviolet sensors, too, if needed.

    Once you spot a likely asteroid, what then?

    EA: We'll send other spacecraft out to intercept and study them. They will be rocket-assisted versions of the telescope - the Arkyd 200 for nearer Earth space, and the Arkyd 300 which is the same except that it will have a deep space communications capability. We'll make sure we understand every cubic inch of that asteroid. We'll find out where it is, what its inertia is, what its spin rate is, whether it has been burned, impacted, or is carbonaceous or metallic. We'll know that asteroid inside and out before we go there and mine it.

    Will you be able to tell, remotely, if a space rock has lucrative platinum deposits, say? CL: Probably not. But we would be able to tell metals from water or silicates. There's an asteroid out in the main belt right now called 24 Themis, and we've been able to sense water ice on its surface from way back here on Earth. Identifying metals will require spectrometry and direct analysis of the materials returned. The Arkyd 300 will get right up to the asteroid, land on it and take samples - like NASA's NEAR and Japan's Hayabusa missions did - then return pictures, data and grain samples back to Earth for analysis.

    Digging up ore on an asteroid 50 to 500 metres wide in zero gravity will be a tough task, even for robots. What technology will you use?

    CL: The data the 300-series gathers will allow us to design the mining spacecraft. There are many, many different options for that. They could vary from very small spacecraft that swarm and cooperate on a bunch of tasks, to very large spacecraft that look seriously industrial. Before we can begin the detailed design of a mining spacecraft, we need to actually go there, explore the asteroid and learn where the specific opportunities are.

    You've suggested an asteroid could be brought closer to the Earth to make it easier to mine. Is that really feasible?

    EA: It is. One of the ways that we could do that is simply to turn the water on an asteroid into rocket fuel and burn it in a thruster that nudges its trajectory. Split water into hydrogen and oxygen, and you get the same fuels that launch space shuttles. Some asteroids are 20 per cent water, and that amount would let you move the thing anywhere in the solar system.

    Another way is to set up a catapult on the asteroid itself and use the thermal energy of the sun to wind up the catapult. Then you throw stuff off in the opposite direction you want the asteroid to go. Conservation of momentum will eventually move the thing forward - like standing on a skateboard and shooting a gun.

    CL: This is not only our view. A Keck Institute "return an asteroid study", involving people at JPL, NASA Johnson Space Center and Caltech, showed that the technology exists to place small asteroids a few metres wide in orbit around the moon for further study.

    Can you think of any other uses for asteroid repositioning?

    EA: There is one incredible concept: we could place the asteroid in an orbit between the Earth and Mars to allow astronauts who want to get there to hop on and off it like a bus. Think about that. You could make a spacecraft out of the asteroid.

    Apart from your commitment to turn a profit for your investors, might there be spin-offs for the rest of us?

    EA: Hopefully, we'll be finding hundreds of new asteroids that would not otherwise have been discovered - including asteroids that are Earth-threatening. We do need to develop the ability to move asteroids: every few hundred years an asteroid strikes that is capable of creating great loss of life and billions of dollars worth of damage. If the 1908 Tunguska meteor had struck London or New York it would have killed millions of people. It is one of the few natural risks we know will happen - the question is when. And we have to be ready for that. So while some might regard moving asteroids as risky, it really is something we need for our planet's future safety.

    What will be your first priority: seeking precious metals or rocket fuel on the asteroids? EA: One of our first goals is to deploy networks of orbital rocket propellant depots, effectively setting up gas stations throughout the inner solar system to open up highways for spaceflight.

    So you are planning filling stations for people like Elon Musk, the SpaceX billionaire planning a crewed mission to Mars?

    EA: Elon and I share a common goal, in fact we share many common goals. But nothing would enable Mars settlement faster than a drastic reduction in the cost of getting to and from the planet, which would be directly helped by having fuel depots throughout the inner solar system.


Who Owns The Minerals?

    Plans to mine minerals on celestial bodies could violate many aspects of international space law.

    SHOULD asteroids rich in precious metals be regarded, in legal terms, like the fish in the sea? That is one approach the United Nations could take as it struggles to come to terms with mining plans announced by Planetary Resources, a start-up company based in Seattle.

    In just under two years, Planetary Resources says it will launch the first of a series of space telescopes into low-Earth orbit in a bid to spot nearby asteroids of a size and mineral composition potentially worth mining. When a strong candidate is found, it plans to dispatch a robotic probe to assess the asteroid's precious metal content, with platinum a priority. If that is found, yet-to-be developed robots will be dispatched to mine it. If it is small enough, the asteroid could be brought into an Earth orbit first, to make the process easier.

    Planetary Resources's plans seem well advanced and others are not far behind. And it's not just asteroids in these firms' sights. Moon Express, a start-up based in Las Vegas, is planning to prospect the moon for platinum and other metals deposited on its surface by meteorites.

    It all sounds mind-bogglingly expensive and complicated, and it is. But those planning the operations have more earthly concerns to deal with, too. Mining asteroids or the moon appears to violate many of the tenets of international space law.

    The most important of these is the UN's Outer Space Treaty of 1967, which in rather pompous language states that "the exploration and use of outer space shall be carried out for the benefit of all countries and shall be the province of all mankind".

    It also specifically prohibits states from making territorial claims in space. "States cannot claim rights over an asteroid," says Joanne Wheeler, a lawyer at London legal practice CMS Cameron McKenna and a UK government adviser on the UN's Committee on the Peaceful Uses of Outer Space. "The Outer Space Treaty says the moon and celestial bodies such as asteroids are not subject to national appropriation. Whether that means no one owns the asteroids, or we all do under some common heritage, what's clear here is there is no state sovereignty over them."

    What applies to sovereign states probably also applies to private companies. "It is not possible for Planetary Resources to say it owns all of an asteroid even if they are the first there," says Wheeler.

    If the ownership of an asteroid is in question, who, then, has legal title to the ores extracted from it and sold back on Earth? Again, it is not clear, though Wheeler points out that there is already a legitimate market for space rocks in the form of meteorites. This probably puts Planetary Resources in the clear.

    Eric Anderson, co-founder of Planetary Resources, doesn't see a problem: "Our analysis shows we have an unequivocal right to mine asteroids. Nothing in the Outer Space Treaty prevents that." He doesn't agree that asteroids, especially those in the 50 to 500-metre size range, are "celestial bodies". Meteorites are fallen asteroids, he says, and they are not regarded as celestial bodies.

    Some even see the treaty as irrelevant to asteroid mining. "The Outer Space Treaty is a paper tiger with no teeth," says Michael Gold, a lawyer specialising in commercial spaceflight in Washington DC. "It's unenforceable and any state can pull out of it with a year's notice. I expect mining capability will trump the law in any situation."

    Whichever interpretation you prefer, it is clear that there is no international regime explicitly governing asteroid mining. "Planetary Resources are in a rather grey zone," says Wheeler. "This is no legal certainty over whether they can do it or not."

    She suggests that a future regime could be based on the law of the sea. "The fish in the high seas are not owned by anyone. You can 'mine' the high seas by taking fish out of them and you can sell them," she says. "Similarly, asteroids might not be owned by anyone but you might be able to mine the resources and then sell them on."

    Mining the moon is also fraught with legal uncertainties. In principle it is governed by an international treaty informally called the Moon Agreement, which seeks to manage our satellite's natural resources. But the treaty is largely worthless because it has not been ratified by any of the spacefaring nations.

    "The Moon Agreement recognises that mining of the moon is about to become feasible," says Wheeler. "But the US, China and Russia are not signatories, so it lacks teeth." The UN is encouraging members to sign, but the concern is that a fait accompli by a mining company could render the treaty moot.

    Finally, what if space mining operations go wrong? If miners cause an asteroid that they have nudged nearer to Earth to plummet into the planet, who would be liable? This is covered by another UN treaty, the Space Liability Convention, which makes the nation that launches a spacecraft liable for damages. "This concept worked back when it was a clear-cut case of governments launching objects, but with many entrepreneurs now launching spacecraft it's getting much more difficult to apportion blame," says Wheeler. As a result, the US and Japan are investigating new liability mechanisms, she says.

    The chances of Planetary Resources causing impacts are minimal, says Timothy Spahr, director of the asteroid-hunting Minor Planet Center at Harvard University. Orbital mechanics are well understood, he says, making asteroid trajectory calculations simple. "Hitting the Earth is a damn hard thing to do."

    Like many astronomers, Spahr has an asteroid named after him. How would he feel about 2975 Spahr being captured and mined? "That's a tough question," he says. "You'd have to ask a lawyer."


Inflatable Space Stations

    THE International Space Station (ISS) is mankind’s holiday house in the sky. Like all such houses, it is a luxury item (costing $150 billion and rising). And like many similar projects on Earth, the owners cannot resist tinkering with it. It was in this spirit that, on January 16th, NASA announced that the ISS is to get an extension. This will not, as might have been the case on Earth, be a conservatory or loft conversion. Instead, it will be a BEAM, or Bigelow Expandable Activity Module.

    Robert Bigelow, an American hotel entrepreneur and space enthusiast, has for years been pushing the idea that space stations should be made not of metal but of fabric. That would mean they could be folded up for launch and inflated in orbit.

    An inflatable space station may sound like the proverbial chocolate teapot, but if you are going to have space stations at all, then inflation is not a bad way of making them. There have been many proposals in the past. Wernher von Braun, the patriotically flexible developer of the V2 military rocket (for Germany) and the Saturn V moon rocket (for America), sketched plans in the 1950s. The Goodyear Aircraft Corporation produced mock-ups in the early 1960s. In the 1980s the Lawrence Livermore National Laboratory came up with a detailed space-exploration plan which relied on inflatable craft, thus quickly attracting the nickname “brilliant condoms”. And in the 1990s NASA proposed sending astronauts to Mars in an inflatable craft called TransHab.

    Despite the branding possibilities offered by the Livermore version of the idea, Mr Bigelow and NASA prefer the less evocative term “expandable module” in their literature. Regardless of the name, however, making spacecraft and space stations out of fabric offers several advantages over the tin-can approach.

    The most important is weight. Inflatable space stations are lighter than metal ones, and even small savings in weight make a big difference to launch costs.

    Expandable modules may be safer, too. Ground tests by Bigelow Aerospace, Mr Bigelow’s vehicle for his orbital ambitions, suggest that the module’s walls—thick sandwiches of exotic fabrics such as Vectran (used in sailcloth and high-strength rope) and Nomex (from which fire-resistant suits are made)—offer better protection than metal ones against impacts from micrometeors and the increasing amount of artificial debris that is in orbit around Earth. They are also less likely than metals to generate dangerous secondary radiation when bombarded with things like cosmic rays. That is one reason why NASA was interested in using inflatable craft for the months-long journey to Mars.

    Nor is the idea untested. In 2006 and 2007 Bigelow launched two unmanned versions, Genesis 1 and Genesis 2. BEAM, which will be bolted onto the space station in 2015, if all goes well, will be the last test of the technology before the launch of the firm’s intended commercial product, the BA-330. This will offer 330 cubic metres of internal space. At the moment the ISS has a volume of 916 cubic metres. The firm plans to launch two BA-330s in 2016, link them together in orbit, and thus create a station with 70% of the pressurised volume of the ISS for a fraction of the cost.

    This first station, dubbed the Alpha Station, will be equipped with laboratory equipment, workbenches and the like. Bigelow hopes to offer 60 days aboard it for around $26m, assuming that its guests make the trip into orbit on one of the cheap rockets provided by SpaceX, another private space company.

    Bigelow hopes in particular to win business from governments without big space programmes of their own. To that end it has memoranda of understanding with several, including those of Britain, Japan and the Netherlands. It is also wooing the private sector, though that may prove tricky. There has long been talk of the advantages of “zero gravity” (actually, the continuous free-fall of orbit, rather than the total absence of a gravitational field) for manufacturing specialised materials whose components are of very different densities, and for growing specialised protein crystals for examination by pharmaceutical companies. This was, indeed, one of the sales pitches for the ISS. Unfortunately, the private sector stayed away in droves, and the scientific output of the ISS has been pitiful.

    If renting the Alpha Station out as a laboratory does not work, there is always the option of turning it into a holiday house. Given Mr Bigelow’s background, it is often assumed that this is the plan anyway. The firm insists that it is not, at least for now. But who will really be interested in paying $26m to go into orbit remains to be seen. Inflated space stations are fine, as long as they do not lead to inflated expectations.


Space Lift For The Moon

    When Neil Armstrong, who died on August 25th (see Obituary), took his giant leap for mankind, he did so from Eagle, a single-use craft of a type known as a lunar excursion module. Eagle, whose job was to ferry Mr Armstrong and his co-pilot Buzz Aldrin the 100km from lunar orbit to the moon’s surface and back, weighed half as much as the command and service module that was waiting in orbit to carry them all the way back to Earth, a journey of almost 400,000km. The weight of the lunar module, on top of the command and service module, was the main reason why the Saturn V rockets that shot Apollo astronauts into space needed to be the tallest, heaviest and most powerful ever flown, a record they still hold.

    Eagle was also a crotchety bird. It overshot the planned landing site, sounded several worrying alarms on its flight, and eventually touched down under manual control with a mere 25 seconds of fuel remaining. How much cheaper and easier (if less dramatic) it would have been if Mr Armstrong and Mr Aldrin could simply have stepped into a lift car in space, pressed M for moon, and descended in tranquillity to the sea of that name. At the 2012 Space Elevator Conference, held in Seattle from August 25th to 27th, much of the buzz was around just such a flight of fancy.

    The idea of a space lift, which goes back to 1959, is to lower a cable from a satellite in orbit around a planet to a base on that planet’s equator. To do this the satellite would need to be in a synchronous orbit (one whose orbital period is the same as the period of revolution of the planet underneath), and the descending cable would have to be counterbalanced by an ascending one extending off into space. Robotic cars would then whizz up and down the descending cable, providing a means of reaching orbit that does not rely on dangerous and expensive rockets.

    The challenge of building such a lift on Earth is immense. It would have to be made from a material at least ten times stronger than any available today to withstand Earth’s gravity. A lunar space lift, by contrast, would have only the moon’s weak gravity to contend with. It could thus be made from existing materials. Dyneema, Kevlar, M5, Spectra and Zylon, all now used for bulletproof waistcoats, have the necessary strength and lightness. Zylon, indeed, has already been deployed on a space mission. It provided the tethers supporting NASA’s Spirit and Opportunity rovers as they dropped by parachute to the plains of Mars.

    At the conference, a group called LiftPort announced it is planning a pilot study of a lunar space lift. It wants to build a robot capable of climbing a 2km-high ribbon of Zylon or similar material (this would be tethered to helium balloons rather than a satellite) in order to test how such a cable responds to stress, strain and sunlight.

    LiftPort’s leader, Michael Laine, thinks that eight years and $800m would be sufficient to construct a lift capable of carrying a 200kg payload to and from the moon using solar energy to run the motors. That would, in principle, enable someone in a spacesuit to make the journey.

    What he would do when he got there, of course, is moot. But Space Adventures, a travel company that has already sent seven tourists into space (one of them twice), thinks there is a market for lunar fly-bys at $150m a pop. Actually walking on the moon would surely command a higher price than that. Even including launch costs, then, it might require only a dozen or so adventurous billionaires to make the venture profitable. Whether Mr Laine’s lunar lift will be built before London has a new airport is questionable. But it might.


Russian Meteorite

 
    On 15 February at 0920 local time, a huge fireball raced across the skies above the Chelyabinsk region of Russia. This meteorite then exploded creating a shockwave that injured more than 1000 people.

    The incident was captured on numerous webcams, security cameras and dashcams in the region and these videos were widely distributed on the web.

    The following day, Stefen Geens, who writes the Ogle Earth blog, pointed out that these cameras formed an ad-hoc sensing network that had gathered significant data about the trajectory and speed of the meteorite. He used this data and Google Earth to reconstruct the path of the rock as it entered the atmosphere and showed that it matched an image of the trajectory taken by the geostationary Meteosat-9 weather satellite.

    Today, Jorge Zuluaga and Ignacio Ferrin at the University of Antioquia in Medellin, Colombia, take this approach a step further by reconstructing the meteorite’s original orbit around the Sun.

    The recordings from traffic cameras have precise locations and well-maintained time stamps. The location of the meteorite impact with the ground is also recorded by a hole in the ice sheet covering Lake Chebarkul, 70km west of Chelyabinsk. Together with the trajectories shown in various YouTube videos, these guys used simple trigonometry to calculate the height, speed and position of the meteorite as it fell to Earth.

    Calculating the rock’s orbit around the Sun is a more complicated affair. This depends on six critical parameters which must all be estimated from the data. Most of these are related to the point at which the meteorite becomes bright enough to cast a noticeable shadow in the videos, its ‘brightening point’. They include the meteorite’s height, elevation and azimuth at this point as well as the longitude and latitude on the Earth’s surface below. The velocity is also crucial.

    “According to our estimations, the Chelyabinski meteor started to brighten up when it was between 32 and 47 km up in the atmosphere,” say Zuluaga and Ferrin, who estimate the velocity at between 13 km/s and 19 km/s relative to Earth.

    They then calculated the likely orbit by plugging these figures into a piece of software developed by the US Naval Observatory called NOVAS, the Naval Observatory Vector Astrometry. This allowed them to include the gravitational influence on the rock of the Moon and the 8 major gravitational bodies in the Solar System.

    Their conclusion is that the Chelyabinsk meteorite is from a family of rocks that cross Earth’s orbit called Apollo asteroids.

    These are well known Earth-crossers. Astronomers have seen over 240 that are larger than 1 km but believe there must be more than 2000 others of similar size out there.

    Smaller Earth crossers are even more common. The sobering news is that astronomers think there are some 80 million about the same size as the one that hit Russia.      
 
 

An Unusual Asteroid

 
    In 2010, a very unusual asteroid was discovered. P/2010 A2 (LINEAR), as it’s named, looked more like a comet: It had a long tail stretching away from it. (Even the name is like a comet’s; the P stands for the “periodic” comet’s orbit.) Observations by Hubble taken a little while later showed it was even weirder: There was a bright dot that was ostensibly the solid part, but it was crisscrossed by streaks that looked as if the object had broken up!

    It’s not a comet, though. Follow-up observations showed no gas at all in the tail as you’d expect from an actual comet; all they revealed was dust consistent with chunks about 1 centimeter across (about the size of a six-sided die) or smaller—the crisscross features were due to chunks of material flung off the main body into space. Clearly, this was an asteroid, not a comet. So why does it have a tail?

    One possible explanation for this bizarre object is that the rock was hit by another smaller asteroid, an impact that would’ve had the explosive yield of a nuclear weapon, disrupting the asteroid and blasting out thousands of tons of dust. Another possible cause is a subtle process called the YORP effect, where the very gentle pressure of sunlight spun up the asteroid, increasing its rotation until it broke apart.

    Observations at the time showed the tail was a few tens of thousands of kilometers long. But new observations taken with the One Degree Imager (ODI) camera on the WIYN telescope show the tail is far longer than first thought: It stretches away from the solid rock by a distance of at least 1 million kilometers, 2 1/2 times the distance from the Earth to the Moon!

    Observations taken over time indicate that whatever event created this tail happened about 3.5 years ago; the tail has been changing with time, giving astronomers a handle on its age. Whatever happened to it happened not long before it was discovered. The fact that the tail is this long is unexpected and will help astronomers understand the asteroid itself as well as the nature of the event that created this display.

    Only a handful objects like this have been seen. Some appear to be asteroids that still have ice frozen in them; those tend to be in the outer part of the asteroid belt, far enough from the Sun that water exists as an ice. P/2010 A2 is inside that line, so any water on it is most likely long gone.

    In 2007, Comet Holmes had a sudden disruptive event that created a huge expanding shell of dust around it that was visible to the naked eye even though the comet was past the orbit of Mars at the time—I saw it myself, and it was amazing. It’s possible that a smaller rock slammed into it, but it may have simply been a buildup of gas inside the comet bursting out.

    We’re still somewhat new at finding objects like this, so we’re still learning about them. We’ve only visited a few comets and asteroids up close, but more space missions are either on their way or being planned for future encounters. These missions will yield huge amounts of knowledge about the leftover debris in our solar system. Asteroids can hit the Earth and cause havoc, they contain vast resources valuable for future crewed space missions, and they hold scientific value as some of the basic and ancient ingredients of the formation of the planets themselves.

    Learning more about them is important for any and all of these reasons. Plus? They’re surprising, and that’s always a great first step on the path to scientific understanding.      
 
 


Pluto

 
    Although billions of kilometers from the sun, frigid Pluto has an Earthly air: an atmosphere made mostly of nitrogen, the same gas that constitutes 78 percent of the air we breathe. But Pluto pursues such an elliptical orbit around the sun that all of that gas might freeze onto its surface when farthest and coldest. On May 4, however, Pluto passed in front of a star in the constellation Sagittarius, allowing observers to watch the atmosphere block some of the star's light and deduce that the air is so substantial it never disappears.

    That passage was key to understanding the atmosphere's future, says Catherine Olkin, a planetary scientist at the Southwest Research Institute in Boulder, Colo., whose team tracked the so-called occultation. In work submitted to Icarus she and her colleagues report that Pluto's atmosphere is now thicker than ever before seen.

    Astronomers discovered the atmosphere in 1988, when Pluto occulted another star. An airless Pluto would have cut off the star's light abruptly, but instead the starlight faded gradually, revealing air with roughly one one-hundred-thousandth the surface pressure of our own—equivalent to the terrestrial atmosphere 80 kilometers high.

    Pluto is so distant that completing a single orbit takes it 248 years. Pluto came closest to the sun in 1989 and has been receding from the star ever since. When Pluto ventures out to its most distant point, in 2113, it will be 3 billion kilometers farther, and sunlight on its surface will be 36 percent weaker, than in 1989. "Many scientists have predicted that Pluto's atmosphere would collapse as it traveled away from the sun," Olkin says. "Receiving less sunlight, the gas would condense onto the surface." Mars, whose orbit is also rather elliptical, temporarily loses a quarter of its air every time its southern hemisphere experiences winter, when Martian gas freezes onto the south polar cap.

    Pluto is mostly rock, but its crust consists of water ice. At Pluto's temperature of approximately 40 kelvins (–233 Celsius), water is as hard as rock, constituting a stage on which nitrogen and also methane dance back and forth between ice and gas.

    The new observations indicate that Pluto's air is now three times denser than in 1988, contradicting models that predicted the atmosphere would someday vanish. Instead, Olkin says, the higher pressure accords with a model indicating that the region around a hundred meters below the surface retains heat during Pluto's close encounters with the sun and releases that heat only slowly, thereby keeping the surface warm enough so that some of the nitrogen always stays gaseous. "As Pluto goes around the sun, its atmosphere does not completely condense," Olkin says. Her work implies that Pluto's water-ice layer is compact, because a porous subsurface would quickly lose its warmth.

    "It's a nice piece of work," says John Stansberry, a planetary scientist at the Space Telescope Science Institute. "These kinds of observations are critical for studying seasonal evolution on Pluto." Stansberry worries, however, that Pluto is more complex than the model assumes, which means the atmosphere's behavior is less clear than Olkin asserts. "Based on these results, it's certainly fair to say that Pluto's atmosphere is not going to collapse any time soon, but to say it's going to be there in 2140 is maybe stretching it a bit," Stansberry says.

    Both Olkin and Stansberry do agree on a far more famous controversy: Pluto is a planet. In 2005 astronomers discovered Eris, a distant world proclaimed to be larger than Pluto, adding to arguments that Pluto should lose its planetary status and prompting predictions that a plethora of worlds surpassing Pluto in size awaited discovery.

    But things didn't work out that way. In 2010 Eris passed in front of a star and failed to live up to the hype. The short duration of the occultation revealed Eris to be just 2,326 kilometers across—versus about 2,350 kilometers for Pluto. And no one has ever found anything else orbiting the sun beyond Neptune's path exceeding Pluto’s size.

    Pluto's diameter, however, is uncertain: It could be as small as 2,300 kilometers or as large as 2,400 kilometers. Ironically, the villain is the atmosphere, which bends starlight during occultations and complicates measurements of its diameter.

    Fortunately, help is on the way. In July 2015 NASA's New Horizons spacecraft will sail past Pluto and its five known moons. "I'm not sure what we'll see, but I can't wait to get there," Olkin says. "It's going to revolutionize our view."      
 
 


Space Elevator Feasibility

 
    Is it time to push the "up" button on the space elevator?

    A space elevator consisting of an Earth-anchored tether that extends 62,000 miles (100,000 kilometers) into space could eventually provide routine, safe, inexpensive and quiet access to orbit, some researchers say.

    A new assessment of the concept has been pulled together titled "Space Elevators: An Assessment of the Technological Feasibility and the Way Forward." The study was conducted by a diverse collection of experts from around the world under the auspices of the International Academy of Astronautics (IAA).

    The study's final judgment is twofold: A space elevator appears possible, with the understanding that risks must be mitigated through technological progress…and a space elevator infrastructure could indeed be built via a major international effort.

    The tether serving as a space elevator would be used to economically place payloads and eventually people into space using electric vehicles called climbers that drive up and down the tether at train-like speeds. The rotation of the Earth would keep the tether taut and capable of supporting the climbers.

    The notion of a beanstalk-like space elevator is rooted in history.

    Many point to the ahead-of-its-time "thought experiment" published in 1895 by Russian space pioneer Konstantin Tsiolkovsky. He suggested creation of a free-standing tower reaching from the surface of Earth to the height of geostationary orbit (GEO; 22,236 miles, or 35,786 km).

    Over the last century or so, writers, scientists, engineers and others have helped finesse the practicality of the space elevator. And the new study marks a major development in the evolution of the idea, says IAA president Gopalan Madhavan Nair.

    "No doubt all the space agencies of the world will welcome such a definitive study that investigates new ways of transportation with major changes associated with inexpensive routine access to GEO and beyond," Nair writes in the new study's preface.

    "There is no doubt that the Academy, due to this study, will contribute to advancing international consensus and awareness on the need to search and develop new ways of transportation in conducting space exploration while preserving our universe in the same way we are now trying to preserve our planet Earth," Nair adds.

    While it's always tricky to predict the future study lead editor Peter Swan told Space.com that space elevators are more than just a science-fiction fantasy. "The results of our study are encouraging," he said.

    Swan's view is fortified by the late science fact/fiction soothsayer, Arthur C. Clarke, who stated in 2003: "The space elevator will be built ten years after they stop laughing…and they have stopped laughing!"

    Swan is chief engineer at SouthWest Analytic Network, Inc. in Paradise Valley, Ariz., and is focused on developing and teaching innovative approaches to "new space" development. He's also head elevator operator of the International Space Elevator Consortium (ISEC), which has organizational members in the United States, Europe and Japan and individual members from around the world.

    ISEC's goal is nothing short of getting a lengthy space elevator built.

    "The question is when, of course," Swan said. "But the point is that the technologies are progressing in a positive manner, such that we who work in it believe that there will be space elevators."

    Swan said the giggle factor regarding space elevators is "down significantly" given work carried out over the last decade by a global network of individuals and groups. "Still, there are many, many issues and I certainly would not want to say that it's not a challenging project."

    The IAA appraisal delves into a number of issues, such as: Why build a space elevator? Can it be done? How would all the elements fit together to create a system of systems? And what are the technical feasibilities of each major space elevator element?

    Two technologies are pacing the development of the space elevator, Swan said.

    Producing an ultra-strong space tether and other space elevator components, Swan said, has been advanced by the invention of carbon nanotubes (CNTs) that are 1,000 times better in strength-to-weight ratio than steel. The good news, he said, is that CNTs are being developed with billions of dollars by nanotechnology, electronics, optics, and materials specialists.

    Similarly, lightweight solar cells "are coming along nicely," Swan said. "That's an industry that the space elevator people are watching, too. We're not going to drive it, but we can certainly watch it and appreciate the advances."

    Money, motivation and desire

    Regarding who would erect a space elevator, Swan said the study dives into details. A primarily commercial effort with some government support is possible, as is a public-private enterprise, or an entirely governmental project.

    "All three are viable. Any one of them could work. It's a matter of money, motivation and the desire to do it," Swan said, though the study centers on commercial development of the space elevator. "It's conceivable all three could be going on at the same time."

    The study team was encouraged by the future, though Swan and others acknowledge there are many questions left to be studied. Indeed, another evaluation of the space elevator idea 10 years hence would be worthwhile, Swan said.

    Erasing the rocket equation

    Are there any technical, political or policy "showstoppers" that could prevent the space elevator from becoming a reality?

    "You're asking the wrong guy," Swan responded. "I am an optimist. I have always had the attitude that good people, motivated by good rationale working hard will make it work. My guess is that space elevators are going to work, whether it's by 2035, 2060 or even 2100."

    Swan said the rationale is moving beyond the "rocket equation," which involves tossing away 94 percent of a rocket's mass sitting on the launch pad.

    "And it still costs a lot of stinking money to get up there," he said.

    The space elevator opens everything up, Swan said. It's a soft ride, a week to GEO. There are no restrictions on the size or shape of payloads.

    "People will laugh and ask why did we ever do space rockets. I's a dumb idea," Swan said. "Space elevators are the answer if we can make them work. Why would you do anything else?"      
 
 


Meteorite Collecting

 
    Laurence Garvie can’t stop thinking about the rock that’s still out there, the one he doesn’t have, the specimen that might explain how the solar system formed or even the origin of life on Earth. That’s why, on a windy February morning in Phoenix, he escorts two men into Arizona State University’s meteorite room, a solid concrete vault lined with metal cabinets containing the collection Garvie manages: thousands of stones from the moon, Mars and the asteroid belt.

    The men bear little resemblance to Garvie, a meteoriticist with a balding pate and too many pens in his pocket. In contrast, Ruben Garcia and Bob Cucchiara are fast-talking meteorite dealers dressed in blue jeans and sweatshirts. They’ve just driven 100 miles from Tucson, where they’ve been scouring the annual Gem, Mineral and Fossil Showcase for meteorites to trade with Garvie. As Cucchiara silently looks over the room, Garcia starts pulling bits of rusty metal out of his pack.

    The metal fragments are a special request. “I called Laurence from the show and asked him what he wanted,” Garcia tells me as he piles them onto a digital scale. Garvie had given him names of several recent finds not yet in the ASU collection. Most of them were discovered in the deserts of northwest Africa, picked up from the sands by local tribesmen and exported to the United States by Moroccan middlemen. Garcia’s rusty specimens are no exception. They come from a meteorite called Agoudal, named after the town in Morocco’s Atlas Mountains where the fragments were recently uncovered, an estimated 40,000 years after impact. Studying the composition of nickel-iron meteorites like Agoudal is the closest scientists can come to sampling Earth’s metal core.

    The deal Garcia and Cucchiara have with meteoriticist Garvie is a barter: rusty chunks of Agoudal in exchange for a few precious brown nodules from the Bondoc meteorite, an ancient 2,000-pound behemoth unearthed in the Philippines and hauled back to Arizona in the ’60s. ASU owns nearly all of Bondoc, far more than researchers will ever need. Since Bondoc is uncommon in private collections, it’s become a sort of asteroidal currency for Garvie, and also for Garcia and Cucchiara. They’ll head back to the Tucson show, where they’ll recover their outlay for the Agoudal they brought by completing a three-way exchange: A collector will get a rare Bondoc trophy piece. Garvie will acquire valuable Agoudal research material. And some Berbers in the Atlas Mountains will continue earning their living by meteorite hunting, discovering space rocks that would otherwise never be found.

    Exchanges like this happen all the time at universities around the world. Unlike paleontologists and archaeologists, who condemn amateur hunters and merchants for destroying excavation sites, many meteoriticists see the commercial traffic in meteorites as a boon — even a necessity — to science. To find a meteorite in the field takes thousands of hours as well as considerable expertise. Few scientists have the time or funding for such expeditions.

    “We are just benefiting from this tremendously as scientists,” says Carl Agee, director of the Institute of Meteoritics at the University of New Mexico. “The rare scientifically valuable specimens that have been found in the past few years have been mind-boggling.”

    While a handful of countries, such as Australia, have banned or severely restricted meteorite exports — and the occasional illicit rock is “found” somewhere other than where it was actually discovered to skirt local law — the vast majority of specimens on the market are legally sourced, exported and sold or traded. And increasingly, those rocks are coming from the arid mountains and deserts of northwest Africa.

    Treasures in the Sand

    Focused around Morocco, northwest Africa is a nebulous geographic designation covering a wide swath of desert. The vagueness reflects an ambiguity about where exactly most northwest African meteorites are found. Except in rare cases like Agoudal, where the discovery site is publicly documented, they’re identified by numbers such as NWA 869. The numbers are assigned by the Meteoritical Bulletin after the rocks have undergone mineralogical analysis and classification by an institution such as ASU.

    While meteorites fall in equal abundance everywhere on Earth, northwest Africa provides especially rich hunting grounds. The dark alien rocks stand out against pale desert sands, and the Sahara’s dry climate preserves them for thousands of years. Yet nomads traveling through the empty desert never thought of collecting them — until recently.

    In 1997, an amateur French digger and dealer named Luc Labenne and his family were in Mauritania, looking to buy excavated prehistoric tools. He heard about meteorites being found in neighboring Algeria and thought it would be worth looking around Mauritania as well. On their fourth trip from France to the region, they found a dark-brown, 55-pound, magnetic rock. The National Museum of Natural History in Paris confirmed that it came from space. Within a month, they’d collected another 210 of the stones.

    In November of the same year, an American meteorite dealer named Edwin Thompson got on a plane bound for Mauritania with $28,000 in cash. A contact he’d made in Morocco earlier, Simon Hmani, had heard of a fireball that nomads tracked to the El Hammami Mountains. There, Hmani negotiated with nomads for a sample and sent it to Thompson. “I thought it was cement,” Hmani recalls. Thompson knew better, and he arranged to buy more than 300 pounds of it.

    Hunters and Gatherers

    Like the stones found by the Labennes, the meteorite discovered in the El Hammami range was of only minor scientific interest: a common type from the asteroid belt known as an ordinary chondrite, already well represented in most museum collections. The real impact was on the market. As the Labennes alerted scientists to how much material could be culled from the desert, Thompson’s cash deal made a strong impression on the nomads. And that was all the motivation they needed. “If you find a meteorite, you make a year’s salary,” Thompson says. He taught the nomads what to look for, and word swiftly spread. By 1998, many English-speaking Moroccans were full-time middlemen. Meteorites were being shipped from Morocco to the Tucson gem show in 55-gallon drums to be picked through by traders like Garcia and Cucchiara.

    In the 16 years that have followed, the volume has only grown. In 1999, 45 northwest African meteorites were classified. Now it’s about 400 per year, but the number doesn’t fully capture the value of what’s coming out of the desert. More extraordinary specimens are being found now than at any other time in history. “The nomads are getting better at looking for meteorites,” observes Hmani. They’ve gotten especially good at identifying stones from the moon and Mars. These rarest of finds seldom look like conventional meteorites and often aren’t attracted to a magnet.

    Garvie says he can see the nomads’ increasing prowess by what arrives in his lab. Other meteoriticists strongly agree. “The meteorite hunters are getting very well educated in practical terms,” says Agee. “If you look at the Martian meteorites that have been discovered, 131 have been classified, and only 27 of them have come from Antarctica,” where all hunting is done by government expeditions, “while the lion’s share is coming from the desert.”

    Finders are loath to reveal their sources, mostly because they want to keep their best fields to themselves. (Large meteoroids often break up in midair, resulting in “strewn fields” where many small meteorites can be found.) But information about a meteorite’s extraterrestrial origin is essential to establishing its value on the market. To get that crucial laboratory classification, the finders or dealers need to send a sample to qualified scientists such as Garvie or Agee, who retain a “type specimen” — customarily 20 grams (about three-quarters of an ounce) or 20 percent of the total weight, whichever is less — as material for research.

    But when scientists agree to classify a specimen, some of them bargain for larger shares or specific cuts, looking for material they can later trade for other meteorites, as Garvie has often done in trades with Garcia and Cucchiara.

    “I won’t [classify] it for 20 grams,” says Garvie. “We negotiate right up front on which pieces I would like, and most dealers are fine with it.” On his desk at ASU are some polished slices of NWA 6991, a speckled, black stone known as a carbonaceous chondrite: the most primitive type of meteorite containing some of the first material from the solar system’s youth. “It’s one of the freshest I’ve ever seen,” he says. “I classified it for the dealer Michael Farmer, and he just says, ‘Take whatever you want.’ ”

    American Souk

    In Tucson, several large men kneel over a row of tattered cardboard boxes under the winter sun. One pulls out a smooth, brown rock, still dusty with desert sand, and spits on it. Running his finger through the saliva, he reaches for the magnifying loupe hanging around his neck, and he squints at the wet spot, slowly turning the stone in the daylight. He grunts and tosses it back. A Moroccan in a traditional turban leans down to offer him the whole crate at a special bargain price. Brushing sand off his flannel shirt and shaking his head, the man walks toward the boxes of another eager Moroccan dealer.

    It’s a typical Saturday morning at the Tucson gem show. For two weeks every February, the expo is spread across the city, occupying the convention center, several motels and even roadside tents, where you can buy everything from dinosaurs to diamonds in the raw. It’s the closest thing in the United States to a Moroccan souk, or bazaar.

    Although meteorites are also traded at annual shows in Denver and Ensisheim in France, and countless items are sold on eBay, this is the world’s biggest marketplace of its kind. Most of the meteorite traders are doing business at the Hotel Tucson City Center, a sprawling complex that rents out all its rooms as makeshift shops. Dealers drape banners over the railings. Luc Labenne and Edwin Thompson have transformed their rooms into full-fledged rock shops with large glass display cases. Many dealers simply spread their merchandise across king-size beds. Some of the Moroccans have so many crates that the beds needed to be stashed away and their piles of merchandise — an unsorted mix of meteorites and ordinary desert rocks — spill out onto the sidewalks outside the motel-style units.

    “A meteorite might pass through five or six hands before it reaches a university,” dealer Garcia explains. With the exception of the nomads and their camels, the whole supply chain — including scientists — comes jostling through those Tucson motels.

    The activity in Tucson is increasing with each passing season. If the first phase of the meteorite boom was characterized by Europeans and Americans traveling to Africa — hunting like Labenne or trading like Thompson — the second phase increasingly involves Africans pushing out into European and American markets.

    But the marketplace has also become more difficult, thanks in part to general unrest and a changing political landscape in the broader region. Labenne stopped visiting after a close friend was thrown into a Sudanese prison. The incident was unrelated to the meteorite trade, but still unsettling for Labenne. Farmer, one of Garvie’s trading partners and one of the few American dealers who still ventures deep into the field on a regular basis, was recently robbed in Kenya by thieves wielding machetes. On another recent trip, he and a partner were locked in an Omani jail cell for two months after local police illicitly confiscated lunar meteorites that Farmer says were worth close to $200,000.

    And yet the incentives, both financial and scientific, are enough to keep hunters like Farmer and researchers like Garvie invested in the meteorite market, and to ensure plenty of business opportunities for dealers like Garcia and Cucchiara. “We need the scientists, and the scientists need us,” Farmer asserts. “Without us, 90 percent of the meteorites would never be seen.”

    The evidence is inside Laurence Garvie’s concrete vault. If not for the rough-and-tumble meteorite business, NWA 6991 would remain out in the desert, and Agoudal would slowly rust away.      
 
 


Eye Problems In Space

 
    You may never have to buy another pair of glasses. Adjustable prescription spectacles commissioned by Nasa for its astronauts could one day become available in high street opticians, according to an eye surgeon working with the space agency.

    The project started when Nasa noticed that astronauts who had spent several months in zero gravity were returning with eye problems. Most had become more long-sighted, while some developed cataracts. Nasa hired Steve Schallhorn, an eye doctor at Optical Express, to investigate what was causing these potentially mission-threatening changes.

    “Nasa has identified that the eye can change in astronauts due to prolonged space travel and these changes can be very significant,” Mr Schallhorn said. “Accordingly, Nasa has embarked on a programme to understand and potentially mitigate against these issues.”

    Scientists believe that the cataracts may begin to form as astronauts are exposed to cosmic rays, streams of minute particles travelling through space with 40 million times the energy found in the particle accelerator at Cern.

    Normally the Earth’s magnetic field blocks this radiation, but once astronauts are in orbit they have little protection. “There are cells in the lens inside our eye that are stimulated by the radiation, and after long-term exposure they can develop a very peculiar kind of cataract,” Mr Schallhorn said.

    The lack of gravity also appears to have a distorting effect on the eyes. “There is still quite a bit we don’t know about this and it is an area of active, ongoing research.” A 2011 survey of 300 astronauts found that almost two thirds of those who had been on long space missions returned with blurrier shortdistance vision. It is thought that this could be caused by a rise in the pressure of the cerebrospinal fluid that sheathes the optic nerve at the back of the eye.

    In an attempt to preserve its cosmonauts’ eyesight on long journeys into deep space, such as its putative mission to Mars, Nasa’s National Space Biomedical Research Institute (NSBRI) commissioned Web Vision Centres, a Utah-based company, to invent a pair of glasses that could adapt to constant changes in the wearer’s focus.

    One possibility is a pair of spectacles that can be adjusted electronically by subtle shifts in the angle of the prisms in the lenses. A simpler option would be magnetic lenses that can be clipped to frames in seconds. Either way, Mr Schallhorn said, the finished article is likely to find its way to patients on Earth.

    The NSBRI has asked other companies to create prototypes of goggles that can gradually adjust the pressure inside the eye by pressing gently on to the cornea, as well as a device that can analyse the back of the eye by reading the light that bounces back off the retina.

    The widespread eye problems represent a serious barrier to space exploration unless they can be corrected, Mr Schallhorn said. “Unless we can get a better handle on understanding the eye changes and discovering effective ways to manage them, it could limit man’s ability to be in space for prolonged periods of time. A Mars mission is going to take several years, and this is one of the main issues they want to get a handle on before humans can be sent to Mars.”


How Likely Is Life On Other Worlds?

    DO WE live on a rare earth? One so exceptional that it is pretty much alone in hosting a rich diversity of life, with almost all other planets being home to simple microbes at best? Or are we in a universe teeming with living things as complex as those here, meaning that we exist as part of a vast, cosmic zoo?

    Debate on this rages on, but we say it is time to accept that the latter is very likely.

    To date we know of at least 3700 exoplanets and there are likely to be trillions of other potentially habitable exoplanets and exomoons in our galaxy and beyond. We do not know how commonly life arises on them, but many scientists think that it may well emerge from the chemical and physical properties of any suitable planet.

    With that in mind, we head to our central question. If a planet does host life, what is that life like? Our hypothesis is that if a life-bearing planet remains habitable for long enough, then complex living things will arise. It might take a long time – for example, oxygen was required for the development of animals on Earth, and it took a billion years of oxygen accumulating in our atmosphere before animals appear in the fossil record. But the jump from simple to complex life will take place, eventually and inevitably.

    How can we claim this? Surely the path that Earth took was unique, full of extraordinarily unlikely events, such as the vast impact early in its history with another protoplanet? It left Earth with an over-sized moon, a big molten iron core, a mantle that can support plate tectonics, lots of water (but not too much), and many other specifics upon which life depends.

    Rare earth contenders are right that our planet is unique, our solar system unlike any other we have found, just as there was only one Bach and one Schubert. But that does not mean that composers are incredibly rare. Other composers from other histories, other traditions, have created music –from Beethoven to boy bands.

    We are not concerned with the specific examples of life on Earth, but with what life does; growing large structures, walking and thinking. For example, the mammalian placenta only evolved once, but similar tissues designed to feed growing embryos have evolved in scorpions, cockroaches, lizards, sharks and snakes. The mammalian eye is unique, but eyes have evolved probably a dozen times. Each specific path is a one-off, but there are many paths to each of these complex functions.

    So what does it take to make a complex organism, such as a Beethoven or a birch tree? There are thousands of specifics, but evolutionary biologists have identified a few key innovations that take life a major step along the path from its simplest form to the diversity we see today.

    Some of those steps are evident in the long hard road to the evolution of a brain: before you can evolve a smart brain, you have to evolve nerve cells, and that means evolving a way to run a complex genetic program in an organism, one that directs cells to form different tissues in different places and at different times. Many of the key steps are actually relatively basic ones even if the end result is far from basic.

    The key innovations on the way to complexity turn out to be light capture (to provide energy), oxygen manufacture (to create a widely available and potent energy source for life to spread), complex cell architecture of the type we see in eukaryotes, multicellularity, genetic structures more sophisticated than a bacterium’s simple DNA, a way to run a complex genetic program, and intelligence. Oh, and sex.

    Looking at these major innovations from the simplest life to the most complex, we find nearly all of them evolved independently several times on Earth. So while these are big steps towards complex life, they are not highly improbable.

    As such, if and when humans visit one of the other inhabited planets, we expect life there could have taken many courses. The biochemistry may be different and life there will certainly have a different anatomy. We may not even recognise the more complex forms as animals or plants, but their functions and what they do are likely to be comparable to the more complex species on Earth.

    Does this mean there would be technological civilisations comparable to ours? Intelligence is quite common on Earth. Tool use, playing, problem solving and the ability to learn new tricks and pass them on have all arisen independently in many animals such as octopuses, parrots, dolphins, apes (including ourselves) and elephants –lineages that have been around for a very long time. So why has just one species followed the evolutionary path towards technological intelligence?

    If complex life is common, this final transition may be what economist Robin Hanson at George Mason University in Virginia calls the “Great Filter”, the stumbling block that makes truly advanced life very rare. If so, it would explain our failure to find any evidence of extraterrestrial technology. Of course, that search is just starting. Thirty years ago we didn’t know of any exoplanets, so who knows what the next generation of New Scientist readers will discover.

    Within decades, the first interstellar probes – planned by NASA and the independent Breakthrough Starshot initiative –may be on their way to the nearest habitable examples. This would be the best way to look for the presence of complex life and test the cosmic zoo hypothesis. Ultimately, though, we may have to accept the idea that the galaxy is a zoo with few visitors, and to find other talking, travelling technologists like ourselves we will have to search in a galaxy far, far away.




Other Resources

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