Long before Planetary Resources was a gleam in the eye of its founders, John Lewis (University of Arizona) wrote a book that put asteroid mining into the public consciousness. Mining the Sky: Untold Riches from the Asteroids, Comets and Planets (Perseus Books, 1996) contains no shortage of wonders, as in the well publicized idea that a single one-kilometer asteroid could produce enough gold and silver to equal world production for a century. David Brin writes about this on George Dvorsky's Sentient Developments site, noting that while that would produce a collapse in gold and silver prices, it would also produce incalculable benefits in terms of raw materials production that could change the economic paradigm entirely. Lewis is a natural fit with Planetary Resources, the highly buzzed-about startup that plans to make asteroid mining a reality, and it's no surprise to see that he serves as one of its advisors. But remembering Mining the Sky, I was startled to discover that the idea of...

On the Trail of the Space Pirates was a 1953 adventure written by Carey Rockwell, a house pseudonym used by a Grosset & Dunlop writer who may or may not have been one Joseph Greene, an editor for the firm in that era. We don't know for sure who 'Carey Rockwell' was and no one has come forward to claim the title, but see the Tom Corbett Space Cadet website for another possible clue to authorship. In any case, On the Trail of the Space Pirates took readers such as my grade school self out into the asteroid belt, where all manner of adventures occur and uranium prospectors ply their trade harassed by evil doers. The asteroids became a lively analogue to the American wild west. Asteroid mining and the culture it spawns has a robust history in science fiction, but I couldn't help recalling this particular book when I read about Planetary Resources and its ambitious plan to mine asteroids. The company's intentions don't extend all the way to the main belt, but focus on asteroids much...

I see that there is a symposium on the MarcoPolo-R mission coming up in late March, which reminds me that at a time when asteroid missions are increasingly in the news, I have yet to cover this one. It was about a year ago that the European Space Agency selected MarcoPolo-R as one of four candidates for a medium-class mission that would launch between 2020 and 2024. The selection doesn't mean the mission has been finalized by any means, only that the four missions chosen will undergo a down-selection process to choose the one to implement. Thus this mission to return a sample of material from a near-Earth asteroid for analysis in ground laboratories will have to prove itself against some formidable competition, including another particularly interesting concept called the Exoplanet Characterisation Observatory (EChO), which would orbit around the L2 Lagrange point and study exoplanet atmospheres. Exoplanets are obviously hot property right now, but asteroids are also having their...

The Dawn spacecraft, orbiting Vesta since July of last year, reached its lowest altitude orbit in December, now averaging 210 kilometers from the asteroid's surface. Ceres is Dawn's next stop, but that journey won't begin until the close-in work at Vesta is complete, with the craft in its low altitude mapping orbit for at least ten weeks and then another period at higher altitudes before Dawn leaves Vesta in late July. The spacecraft's Gamma Ray and Neutron Detector (GRaND) instrument is already telling us much about the giant asteroid's surface composition. In fact, the five weeks of mapping at low-altitude have provided the first look at global-scale variations on Vesta. GRaND measures the abundance of elements found in planetary surfaces, and while its investigations are still in the early stages of analysis, it's clear that Vesta's surface varies widely as opposed to the mostly uniform composition of smaller asteroids. We know that Vesta developed a core, mantle and crust, making...

This morning we stick with the planetary migration theme begun on Friday, when the subject was a possible ice giant that was expelled from the Solar System some 600 million years after formation. We have a lot to learn about the mechanisms that could force such ejections, but it's becoming clear that objects up to planet size do indeed migrate, as witness the latest findings on the asteroid Lutetia. Using spectral information put together from space- and ground-based telescopes including ESA's Rosetta spacecraft, scientists have determined that Lutetia is a fragment of the same inner system material that went into the inner rocky planets. A gravitational encounter somewhere in the inner system would then have propelled it outward to the Main Belt. The observations pulled together data in visible, ultraviolet, near-infrared and mid-infrared wavelengths. The only kind of meteorite that matches the spectrum of Lutetia exactly is the type known as enstatite chondrites, known to be...

2005 YU55, an asteroid roughly the size of a city block, makes its closest pass today, approaching within 325,000 kilometers, closer than the distance between the Earth and the Moon. It will be another seventeen years before we get an asteroid as substantial as this in such proximity. That one is 2001 WN5, which will pass halfway between the Moon and the Earth in 2028. Today's object of interest, 2005 YU55, isn't in danger of hitting the Earth on this pass, but astronomers track these objects closely because over time their trajectories are known to change. Image: This radar image of asteroid 2005 YU55 was obtained on Nov. 7, 2011, at 11:45 a.m. PST (2:45 p.m. EST/1945 UTC), when the space rock was at 3.6 lunar distances, which is about 860,000 miles, or 1.38 million kilometers, from Earth. Image credit: NASA/JPL-Caltech. The asteroid's discoverer, Robert McMillan (University of Arizona) calls it "...one of the potentially hazardous asteroids that make close approaches from time to...

Getting water into the inner Solar System is an interesting exercise. There has to be a mechanism for it, because the early Earth formed at temperatures that would have caused any available water to have evaporated. Scientists have long speculated that water must have been delivered either through comets or asteroids once the Earth had cooled enough to allow liquid water to exist. The former was preferred because the water content in comets is so much higher than in asteroids. But the theory had problems, not the least of which was that comets studied in this regard showed deuterium levels twice that of Earth's oceans. The ratio of deuterium and hydrogen, both made just after the Big Bang, can vary in water depending on its location because local conditions can affect the chemical reactions that go into making ice in space. A comparison of the deuterium to hydrogen ratio in extraterrestrial objects can be compared to water found in Earth's oceans to identify the source of our water....

With a fierce interest in nearby brown dwarfs, I often neglect the significant part of the WISE mission devoted to asteroids. WISE (Wide-Field Infrared Explorer) has catalogued more than 157,000 asteroids in the main belt and discovered 33,000 new objects as part of its NEOWISE activities. Here the benefits of infrared wavelengths become apparent, for we know little about the reflectivity of a given asteroid and thus have trouble figuring out how large it is. Using infrared, WISE can relate light in these frequency ranges to the size and temperature of the object. Having established size, mission scientists can re-calculate the asteroid's reflectivity. NEOWISE is actually an enhancement to the WISE data processing system that makes for better detection of moving objects in the WISE data. In addition to the asteroids mentioned above, NEOWISE has also detected more than 500 Near-Earth Objects (NEOs) and roughly 120 comets. We've had plentiful studies at visible wavelengths from groups...

We've talked often in these pages about Near Earth Objects (NEOs) and the potential danger posed not just by them but by objects from much further out in the Solar System if they were to take an Earth-crossing trajectory. But it's also true that NEOs have a certain allure even if they are potentially dangerous. They're close enough to consider a manned mission, and even a small 2-kilometer sized metallic NEO could contain rich metals and minerals worth trillions of dollars. Of course, what metals markets would do if we suddenly had access to such an object is another matter. And mining an NEO, not a new concept, is still on the impractical side. But Hexi Baoyin (Tsinghua University, Beijing) and colleagues are proposing a possible solution. The temporary capture into Earth orbit of an NEO by creating a small velocity change could allow a relatively low-cost trajectory to the object that would provide mining opportunities. And indeed, various asteroid deflection schemes from solar...

One of the more intriguing issues for the Wide-field Infrared Survey Explorer (WISE) satellite is the question of nearby objects that might be causing problems with the Oort Cloud. Specifically, we're interested in learning whether an object like the hypothesized 'Nemesis' -- a tiny companion star to the Sun -- or a closer gas giant ('Tyche') -- might cause disruption to cometary orbits that would create episodes in which more comets than usual make their way into the inner Solar System. Find such an object and you may be able to explain what some have been arguing, that there are periodic variations in the timing of giant impacts, a regular and revealing pattern. Of course, periodic changes in the frequency of impacts could be caused by something other than a companion star or unknown planet. Another suggested mechanism is the motion of our Solar System through the main plane of the Milky Way, causing the gravitational influence of nearby stars to tug on Oort Cloud comets on a...

Although the asteroid temporarily called 2010 TK7 was discovered late in 2010, we now learn in the latest issue of Nature that this object is our planet's first known Trojan asteroid. The term refers to objects that orbit around one of the two Lagrangian points L4 and L5 -- these are found 60° ahead of and behind the larger body. Trojans come in various sizes. The Saturn system actually has Trojan moons (Telesto and Calypso, which accompany Tethys, and Helene and Polydeuces, which move in orbital configuration with Dione). Jupiter, Neptune, Mars and now the Earth have all been found to have Trojan asteroids associated with them. As the paper on this work points out, the viewing geometry poses problems for discovering Trojan asteroids moving with our planet, although we have found unusual objects like the 'horseshoe orbiters' 2010 SO16 and 3753 Cruithne. What made the current discovery possible was the Wide-field Infrared Survey Explorer (WISE) satellite, which searched large...

Asteroid 1999 RQ36 may or may not pose a future problem for our planet -- the chances of an impact with the Earth in 2182 are now estimated at roughly one in 1800. But learning more about it will help us understand the population of near-Earth objects that much better, one of several reasons why the OSIRIS-REx mission is significant. The acronym stands for Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer, a genuine mouthful, but a name we'll be hearing more of as the launch of this sample-return mission approaches in 2016. The target asteroid, 575 meters in diameter, has been the subject of extensive study not only by ground-based telescopes including the Arecibo planetary radar but also by the Spitzer Space Telescope. We know that 1999 RQ36 orbits the Sun every 1.2 years and crosses the Earth's orbit every September, with a shape and rotation rate that are well understood. OSIRIS-REx will carry pristine samples of carbonaceous materials of a...

With asteroid 2005 YU55 making a close pass later this year, it's worth remembering that we've had a look at this near-Earth object before. It was in April of 2010 that the asteroid, discovered through the efforts of the SpaceWatch Program at the University of Arizona, was deftly imaged by the Arecibo Radio Telescope. That first look was helpful in several ways, the most immediate being that it allowed scientists to rule out the possibility of an Earth impact for the next 100 years. The radar image is fuzzy, but bear in mind that this is an object no more than 400 meters in size, and as the 7.5-meters-per-pixel resolution can make out, it's spherical in shape. Image: This radar image of asteroid 2005 YU55 was generated from data taken in April of 2010 by the Arecibo Radar Telescope in Puerto Rico. Image credit: NASA/Cornell/Arecibo. The next close pass will be on November 8, when 2005 YU55 will close to within about 325,000 kilometers. And this time around, we should learn a great...

The Earth is followed around the Sun by several Near Earth Asteroids in what are called 'horseshoe orbits.' Have a look at the NASA image below showing the orbital contours of such orbits. You can see the horseshoe shape, so called because the object's apparent direction changes as seen by a viewer on the Earth. What's happening is that the gravitational attraction of the Earth is changing the asteroid's elliptical orbit. Even though the asteroid always orbits the Sun in the same direction, it cycles between catching up with the Earth and falling behind. It's the relative motion of the object with relation to both the Sun and the Earth that produces the horseshoe effect. Image: Starting out at point A on the inner ring between L5 and Earth, the satellite is orbiting faster than the Earth. It's on its way toward passing between the Earth and the Sun. But Earth's gravity exerts an outward accelerating force, pulling the satellite into a higher orbit which - counter-intuitively -...

We're starting to get a look at imagery from the Stardust spacecraft's close approach to comet Tempel 1, which occurred this morning at about 0439 UTC (2339 EST). The mission is an extension for the comet-chasing spacecraft, which flew past comet Wild 2 in 2004 and collected samples from the cometary coma that were subsequently returned to Earth. This time we're returning to a previously visited comet, the site of the Deep Impact spacecraft's encounter in 2005. You'll recall that on that mission, an impactor was driven into the comet. Scientists are interested in learning what changes have occurred in the interval between visits, and possibly examining the crater. Image: NASA's Stardust-NExT mission transmitted the first image it took during its approach to comet Tempel 1 at 8:35 p.m. PST (11:35 p.m. EST) on Feb. 14, 2011, from a distance of approximately 2,462 kilometers (1,530 miles). The comet was first visited by NASA's Deep Impact mission in 2005. Credit:...

The asteroid Apophis is extremely unlikely to hit the Earth any time soon, but we do know that it's slated to make two close passes, closing to a distance of 36,000 kilometers or so in 2029 and again in 2036. These events should give us pause -- this is an object some 335 meters in diameter weighing an estimated 25 million tons. It's 90 stories tall, if you like to think in skyscraper terms, which is what Greg Matloff probably likes to do, given that the physicist and asteroid deflection expert works at New York City College of Technology (City Tech). Of Apophis, Matloff says, "We don't always know this far ahead of time that they're coming, but an Apophis impact is very unlikely." A good thing, too, for a strike by an object of this size would be catastrophic. This City Tech news release offers a look at Matloff's ideas on what to do if we find a Near-Earth Object on a collision course. He's a proponent of diverting rather than destroying such objects because of the potential for...

The asteroid that crashed into the Nubian desert in the fall of 2008 turns out to be more interesting than we first realized. You'll recall that the 59-ton object was first detected by the Catalina Sky Survey (another reassuring instance of the CSS doing its job, as discussed in a recent post). That allowed astronomers to track the asteroid immediately before its plunge into the Earth's atmosphere, a first for this kind of observation. In addition, it was possible to create a search grid that Peter Jenniskens (NASA Ames) was able to use in guiding a recovery team in the Sudanese desert. Four expeditions later, 600 meteorite fragments are now at our disposal. This short film was made during the effort, giving an idea of conditions in the search field. [youtube FFW5uwkG0fs 500 416] A close examination of these fragments reveals the interesting fact that the asteroid (2008 TC3) contained at least ten different kinds of meteorites, some containing chemicals that form life's building...

It's good to see asteroid deflection occasionally popping up in the news, thanks to the efforts of people like former astronaut Rusty Schweickart, whose efforts as co-chairman of the Task Force on Planetary Defense of the NASA Advisory Council are complemented by his work for non-profits like the B612 Foundation. Schweickart is worried about the potential consequences of even a small asteroid impact, pointing to the Tunguska event of 1908, in which 800 square miles of Siberian forest were flattened in the kind of strike that occurs every 200 to 300 years. Bigger asteroids are, obviously, a far greater danger, and while they're much rarer, they do have the capability of wiping out entire species, as may well have occurred some 65 million years ago in the destruction of the dinosaurs. In his recent New York Times article, Schweickart notes what we need to do: With a readily achievable detection and deflection system we can avoid their same fate. Professional (and a few amateur)...

A manned mission to an asteroid sounds, on first hearing, like a true deep-space venture, and in the days when we thought of the asteroids as largely confined to a belt between Mars and Jupiter, so it would have been depicted. But today we know that a large population of near-Earth objects (NEOs) is out there, close enough to make one of them the most obvious target for a mission beyond the Earth-Moon system. Moreover, they're a necessary target given our need to understand their composition in case we ever have to change an asteroid trajectory. Even so, you don't send a human team to a completely unknown destination, which is why robotic asteroid exploration continues to loom large. Two missions -- Japan's Hayabusa and NASA's Near Earth Asteroid Rendezvous (NEAR) -- have actually orbited and landed on an asteroid. Now the Applied Physics Laboratory at Johns Hopkins University is proposing a follow-on to the NEAR mission that would give us the needed insights for later human visits....

NASA's workshop on identifying objectives for missions to near-Earth objects will be held next week, August 10-11 at the Renaissance Mayflower Hotel in Washington, DC. We can hope that this gathering of NASA leaders, academics, and space experts from across the international community will help keep the public's attention on the need for such missions. Part of the reason for having the workshop is to communicate NASA's preliminary plans for a human mission to an NEO, a useful step as we build expertise about these objects and ponder strategies to handle any future impact scenarios. You can follow the video stream at the appropriate time here. Meanwhile, the continuing survey of near-Earth objects has produced another one, asteroid 101955 1999 RQ36, with a slight impact possibility in 2182. We can call this object a Potentially Hazardous Asteroid (PHA) based on the results from the two mathematical models -- Monte Carlo Method and line of variations sampling -- being used to study it....