Alien-hunting equation revamped for mining asteroids

The solar system is littered with millions of asteroids, but only a few can be profitably mined for valuable metals and water using current technology. That is the conclusion of a new analysis inspired by the search for life on other planets.

Recent years have seen two US companies – Planetary Resources and Deep Space Industries – established with the intent of one day mining space rocks. NASA also has asteroid ambitions, with a plan to drag one into lunar orbit for astronauts to study.

“People tend to lump it all together and say ‘Oh, there’s trillions of dollars of resources up in space’,” says Martin Elvis of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. But it is still unclear which rocks will make the best targets.

To tackle the problem, Elvis adapted a tool used to study another cosmic puzzle: the Drake equation, used in the hunt for alien life. Dreamed up in 1961 by astronomer Frank Drake, the equation provides an estimate of the number of detectable alien civilisations in the Milky Way. You just need to plug in realistic guesses for the equation’s various factors.
drakeElvis’s equation – shown above and detailed in an upcoming edition of Planetary and Space Science – works in a similar way. It calculates the number of mineable asteroids for a given resource by combining key factors: the asteroid’s type, its richness in resources, and the practical limitations to mining it.

First up is the asteroid’s type, which determines composition. Based on previous surveys, Elvis estimates that 4 per cent of space rocks are the right type to contain platinum and similarly valuable metals. Of these, he says, half will have a rich enough concentration of metal to be worth mining.

Got to get there

Of course, companies have to reach an asteroid to mine it. The limiting factor is the energy needed to get to an asteroid with enough mining equipment and return with the mined ore, meaning only 2.5 per cent of asteroids are accessible from Earth.

The rock must also be large enough to justify the mining expedition in the first place, so Elvis considers the fraction of asteroids larger than 100 metres in diameter, which if fully mined for platinum would be worth a little over a billion dollars at current market prices.

Putting this all together, Elvis says there are only 10 asteroids worth mining for platinum, and 18 for water for future space colonies. Engineering difficulties could make these numbers even lower. Asteroid miners should be cautious in evaluating their plans, Elvis says, as the true value could turn out to be zero.

“There’s a lot of commonality between Martin’s analyses and our own research,” says Chris Lewicki, president of Planetary Resources. He says that efforts to characterise the ore-content of asteroids may be simpler than the detailed science missions so far conducted by governments. “This may afford the opportunity for more cost-effective types of instrumentation, where the goal is simply to qualify a resource for follow-up study.”

The new approach addresses an important question, says Daniel Garcia Yarnoz at the University of Strathclyde in Glasgow, UK, though it is difficult to know the real numbers. “It relies greatly on assumptions on various factors, in particular the probability that the asteroid is resource-rich.”

Astronomers surprised by large space rock less dense than water

Kuiper belt object challenges planet-formation theories.

The Kuiper belt counts at least 70,000 objects with diameters larger than 100 kilometres, orbiting the Sun at least 30 times farther than does the Earth. ARTIST'S IMPRESSION DETLEV VAN RAVENSWAAY/SCIENCE PHOTO LIBRARY

The Kuiper belt counts at least 70,000 objects with diameters larger than 100 kilometres, orbiting the Sun at least 30 times farther than does the Earth.

A planetary scientist has identified the largest-known solid object in the Solar System that could float in a bathtub. The rock-and-ice body, which circles well outside the orbits of the planets, is less dense than water — although a bathtub big enough to hold it would stretch from London to Frankfurt.

The body, dubbed 2002 UX25, lies in the Kuiper belt, a reservoir of dwarf planets, comets and smaller frozen bodies beyond the orbit of Neptune. The object’s low density and size — it is 650 kilometres wide — seem to conflict with a leading model for the formation of large solid bodies in the Kuiper belt and throughout the Solar System. Planetary scientist Michael Brown of the California Institute of Technology in Pasadena reports its density measurement in an upcoming issue of The Astrophysical Journal Letters, with a preprint available on the arXiv online repository (“The density of mid-sized Kuiper belt object 2002 UX25 and the formation of the dwarf planets”, Michael E. Brown)

Densities of objects in and from the Kuiper belt. In most cases, the uncertainty in diameter is much larger than the uncertainty in mass, so the density-diameter uncertainty lies along a curved path. Quaoar has a larger mass uncertainty than most other objects, and that full uncertainty is show as a vertical error bar at the position of Quaoar. Two possible density-radius solutions are show for Orcus, one where Orcus and its satellite Vanth have equal albedos (the less dense solution) and one where Vanth has a lower albedo more typical of smaller KBOs (the more dense solution).

Densities of objects in and from the Kuiper belt. In most cases, the uncertainty in
diameter is much larger than the uncertainty in mass, so the density-diameter uncertainty
lies along a curved path. Quaoar has a larger mass uncertainty than most other objects, and
that full uncertainty is show as a vertical error bar at the position of Quaoar. Two possible
density-radius solutions are show for Orcus, one where Orcus and its satellite Vanth have
equal albedos (the less dense solution) and one where Vanth has a lower albedo more typical
of smaller KBOs (the more dense solution).

Because objects in the Kuiper belt are believed to have changed relatively little since the early years of the Solar System, the region “offers our best chance to comprehend how the early stages of planet formation unfold”, says planetary scientist Andrew Youdin of the University of Colorado Boulder.

According to the leading model, small dust particles in the swirling disk that surrounded the infant Sun gradually collided and coalesced to form bigger particles. This process ultimately built dwarf planets in the Kuiper belt, such as Pluto, as well as Earth and the other rocky planets in the inner Solar System.

If large bodies in the Kuiper belt were made by the merging of small ones, the densities of the small and big bodies should be related. But objects in the Kuiper belt with diameters of less than 350 km all seem to be less dense than water, whereas those with diameters greater than 800 km seem to be denser than water.

The 650-kilometre-wide object 2002 UX25 as seen by the Hubble Space Telescope. NASA/ M. BROWN

The 650-kilometre-wide object 2002 UX25 as seen by the Hubble Space Telescope.

Density dispute
One possible explanation for the mismatch is that the smaller objects are more porous, whereas the stronger gravity of the bigger objects packs ice and rock more tightly, creating a denser structure. But for that scenario to hold true, medium-sized bodies — those with diameters of around 600 km — should have a density that is midway between the smaller and larger bodies.

That turns out not to be the case if 2002 UX25 — the first intermediate-size Kuiper belt object to have its density measured — is typical of the vast number of similarly sized objects in the belt. On the basis of measurements made with several space- and ground-based telescopes, the object has a density of 0.82 grams per cubic centimetre — 18% lower than that of water.

The low density suggests that 2002 UX25 consists mainly of ice, making it difficult to understand how larger, more rocky objects could form from the merging of smaller bodies in the Kuiper belt, notes Brown.

But an alternative theory proposed by Youdin and a colleague could explain the results. According to his theory, the large Kuiper belt objects formed first. They were rapidly built from pebble-sized pieces of rock or ice that were forced to clump together by turbulent, swirling eddies in the Sun’s primordial, planet-making disk. Collisions between the large objects chipped away at their icy exteriors, forming the small, low-density Kuiper belt members and leaving behind large, rock-rich bodies.

To corroborate that theory, scientists will need to measure the density of more Kuiper belt objects that have a size similar to 2002 UX25, says Youdin. But even if the body turns out to be an oddball, he adds, its extremely low density “can’t be easily dismissed”.


New Imagery of Asteroid Mission

arv-orion_0NASA released Aug. 22 new photos and video animations depicting the agency’s planned mission to find, capture, redirect, and study a near-Earth asteroid. The images depict crew operations including the Orion spacecraft’s trip to and rendezvous with the relocated asteroid, as well as astronauts maneuvering through a spacewalk to collect samples from the asteroid.

Concept animation showing the crew operations on NASA’s proposed Asteroid Redirect Mission:


NASA Radar Reveals Asteroid Has Its Own Moon

First radar images of asteroid 1998 QE2 were obtained when the asteroid was about 3.75 million miles (6 million kilometers) from Earth. Image credit: NASA/JPL-Caltech/GSSR

First radar images of asteroid 1998 QE2 were obtained when the asteroid was about 3.75 million miles (6 million kilometers) from Earth. Image credit: NASA/JPL-Caltech/GSSR

PASADENA, Calif. — A sequence of radar images of asteroid 1998 QE2 was obtained on the evening of May 29, 2013, by NASA scientists using the 230-foot (70-meter) Deep Space Network antenna at Goldstone, Calif., when the asteroid was about 3.75 million miles (6 million kilometers) from Earth, which is 15.6 lunar distances.

The radar imagery revealed that 1998 QE2 is a binary asteroid. In the near-Earth population, about 16 percent of asteroids that are about 655 feet (200 meters) or larger are binary or triple systems. Radar images suggest that the main body, or primary, is approximately 1.7 miles (2.7 kilometers) in diameter and has a rotation period of less than four hours. Also revealed in the radar imagery of 1998 QE2 are several dark surface features that suggest large concavities. The preliminary estimate for the size of the asteroid’s satellite, or moon, is approximately 2,000 feet (600 meters) wide. The radar collage covers a little bit more than two hours.

The radar observations were led by scientist Marina Brozovic of NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

The closest approach of the asteroid occurs on May 31 at 1:59 p.m. Pacific (4:59 p.m. Eastern / 20:59 UTC), when the asteroid will get no closer than about 3.6 million miles (5.8 million kilometers), or about 15 times the distance between Earth and the moon. This is the closest approach the asteroid will make to Earth for at least the next two centuries. Asteroid 1998 QE2 was discovered on Aug. 19, 1998, by the Massachusetts Institute of Technology Lincoln Near Earth Asteroid Research (LINEAR) program near Socorro, N.M.

The resolution of these initial images of 1998 QE2 is approximately 250 feet (75 meters) per pixel. Resolution is expected to increase in the coming days as more data become available. Between May 30 and June 9, radar astronomers using NASA’s 230-foot-wide (70 meter) Deep Space Network antenna at Goldstone, Calif., and the Arecibo Observatory in Puerto Rico, will perform an extensive campaign of observations on asteroid 1998 QE2. The two telescopes have complementary imaging capabilities that will enable astronomers to learn as much as possible about the asteroid during its brief visit near Earth.

Radar is a powerful technique for studying an asteroid’s size, shape, rotation state, surface features and surface roughness, and for improving the calculation of asteroid orbits. Radar measurements of asteroid distances and velocities often enable computation of asteroid orbits much further into the future than if radar observations weren’t available.

NASA places a high priority on tracking asteroids and protecting our home planet from them. In fact, the United States has the most robust and productive survey and detection program for discovering near-Earth objects. To date, U.S. assets have discovered more than 98 percent of the known Near-Earth Objects.

In 2012, the Near-Earth Object budget was increased from $6 million to $20 million. Literally dozens of people are involved with some aspect of near-Earth object research across NASA and its centers. Moreover, there are many more people involved in researching and understanding the nature of asteroids and comets, including those objects that come close to Earth, plus those who are trying to find and track them in the first place.

In addition to the resources NASA puts into understanding asteroids, it also partners with other U.S. government agencies, university-based astronomers, and space science institutes across the country that are working to track and better understand these objects, often with grants, interagency transfers and other contracts from NASA.

NASA’s Near-Earth Object Program at NASA Headquarters, Washington, manages and funds the search, study, and monitoring of asteroids and comets whose orbits periodically bring them close to Earth. JPL manages the Near-Earth Object Program Office for NASA’s Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena.

In 2016, NASA will launch a robotic probe to one of the most potentially hazardous of the known Near-Earth Objects. The OSIRIS-REx mission to asteroid (101955) Bennu will be a pathfinder for future spacecraft designed to perform reconnaissance on any newly-discovered threatening objects. Aside from monitoring potential threats, the study of asteroids and comets enables a valuable opportunity to learn more about the origins of our solar system, the source of water on Earth, and even the origin of organic molecules that lead to the development of life.

Asteroid belts of just the right size are friendly to life

This illustration shows three possible scenarios for the evolution of asteroid belts. In the top panel, a Jupiter-size planet migrates through the asteroid belt, scattering material and inhibiting the formation of life on planets. The second scenario shows our solar-system model: a Jupiter-size planet that moves slightly inward but is just outside the asteroid belt. In the third illustration, a large planet does not migrate at all, creating a massive asteroid belt. Material from the hefty asteroid belt would bombard planets, possibly preventing life from evolving. Credit: NASA/ESA/A. Feild, STScI

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NASA’s WISE Colors in Unknowns on Jupiter Asteroids

Trojan Colors Revealed (Artist’s Concept) –

Scientists using data from NASA’s Wide-field Infrared Survey Explorer, or WISE, have uncovered new clues in the ongoing mystery of the Jovian Trojans — asteroids that orbit the sun on the same path as Jupiter. Like racehorses, the asteroids travel in packs, with one group leading the way in front of the gas giant, and a second group trailing behind.

The observations are the first to get a detailed look at the Trojans’ colors: both the leading and trailing packs are made up of predominantly dark, reddish rocks with a matte, non-reflecting surface. What’s more, the data verify the previous suspicion that the leading pack of Trojans outnumbers the trailing bunch.

The new results offer clues in the puzzle of the asteroids’ origins. Where did the Trojans come from? What are they made of? WISE has shown that the two packs of rocks are strikingly similar and do not harbor any “out-of-towners,” or interlopers, from other parts of the solar system. The Trojans do not resemble the asteroids from the main belt between Mars and Jupiter, nor the Kuiper belt family of objects from the icier, outer regions near Pluto.

“Jupiter and Saturn are in calm, stable orbits today, but in their past, they rumbled around and disrupted any asteroids that were in orbit with these planets,” said Tommy Grav, a WISE scientist from the Planetary Science Institute in Tucson, Ariz. “Later, Jupiter re-captured the Trojan asteroids, but we don’t know where they came from. Our results suggest they may have been captured locally. If so, that’s exciting because it means these asteroids could be made of primordial material from this particular part of the solar system, something we don’t know much about.” Grav is a member of the NEOWISE team, the asteroid-hunting portion of the WISE mission.

The first Trojan was discovered on Feb. 22, 1906, by German astronomer Max Wolf, who found the celestial object leading ahead of Jupiter. Christened “Achilles” by the astronomer, the roughly 220-mile-wide (350-kilometer-wide) chunk of space rock was the first of many asteroids detected to be traveling in front of the gas giant. Later, asteroids were also found trailing behind Jupiter. The asteroids were collectively named Trojans after a legend, in which Greek soldiers hid inside in a giant horse statue to launch a surprise attack on the Trojan people of the city of Troy.

“The two asteroid camps even have their own ‘spy,'” said Grav. “After having discovered a handful of Trojans, astronomers decided to name the asteroid in the leading camp after the Greek heroes and the ones in the trailing after the heroes of Troy. But each of the camps already had an ‘enemy’ in their midst, with asteroid ‘Hector’ in the Greek camp and ‘Patroclus’ in the Trojan camp.”

Other planets were later found to have Trojan asteroids riding along with them too, such as Mars, Neptune and even Earth, where WISE recently found the first known Earth Trojan: .

Before WISE, the main uncertainty defining the population of Jupiter Trojans was just how many individual chunks were in these clouds of space rock and ice leading Jupiter, and how many were trailing. It is believed that there are as many objects in these two swarms leading and trailing Jupiter as there are in the entirety of the main asteroid belt between Mars and Jupiter.

To put this and other theories to bed requires a well-coordinated, well-executed observational campaign. But there were many things in the way of accurate observations — chiefly, Jupiter itself. The orientation of these Jovian asteroid clouds in the sky in the last few decades has been an impediment to observations. One cloud is predominantly in Earth’s northern sky, while the other is in the southern, forcing ground-based optical surveys to use at least two different telescopes. The surveys generated results, but it was unclear whether a particular result was caused by the problems of having to observe the two clouds with different instruments, and at different times of the year.

Enter WISE, which roared into orbit on Dec. 14, 2009. The spacecraft’s 16-inch (40-centimeter) telescope and infrared cameras scoured the entire sky looking for the glow of celestial heat sources. From January 2010 to February 2011, about 7,500 images were taken every day. The NEOWISE project used the data to catalogue more than 158,000 asteroids and comets throughout the solar system.

“By obtaining accurate diameter and surface reflectivity measurements on 1,750 Jupiter Trojans, we increased by an order of magnitude what we knew about these two gatherings of asteroids,” said Grav. “With this information, we were able to more accurately than ever confirm there are indeed almost 40 percent more objects in the leading cloud.”

Trying to understand the surface or interior of a Jovian Trojan is also difficult. The WISE suite of infrared detectors was sensitive to the thermal glow of the objects, unlike visible-light telescopes. This means WISE can provide better estimates of their surface reflectivity, or albedo, in addition to more details about their visible and infrared colors (in astronomy “colors” can refer to types of light beyond the visible spectrum).

“Seeing asteroids with WISE’s many wavelengths is like the scene in ‘The Wizard of Oz,’ where Dorothy goes from her black-and-white world into the Technicolor land of Oz,” said Amy Mainzer, the principal investigator of the NEOWISE project at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “Because we can see farther into the infrared portion of the light spectrum, we can see more details of the asteroids’ colors, or, in essence, more shades or hues.”

The NEOWISE team has analyzed the colors of 400 Trojan asteroids so far, allowing many of these asteroids to be properly sorted according to asteroid classification schemes for the first time.

“We didn’t see any ultra-red asteroids, typical of the main belt and Kuiper belt populations,” said Grav. “Instead, we find a largely uniform population of what we call D-type asteroids, which are dark burgundy in color, with the rest being C- and P-type, which are more grey-bluish in color. More research is needed, but it’s possible we are looking at the some of the oldest material known in the solar system.”

Scientists have proposed a future space mission to the Jupiter Trojans that will gather the data needed to determine their age and origins.

The results were presented today at the 44th annual meeting of the Division for Planetary Sciences of the American Astronomical Society in Reno, Nev. Two studies detailing this research are accepted for publication in the Astrophysical Journal.
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