The Barberton greenstone belt is considered one of the oldest pieces of continental crust on the planet. About 100 kilometers long and 60 kilometers wide, the belt is in South Africa east of Johannesburg and not far from the border of Swaziland, a region where gold was first discovered in South Africa. Greenstone belts, however, are numerous, widely distributed geographically and throughout geological history, all of them marked by the characteristic green hue imparted by the metamorphic minerals within their rocks. The Barberton greenstone belt is now yielding evidence of a massive ancient impact well over three billion years old. The paper on this work is slated to appear in the journal Geochemistry, Geophysics, Geosystems, where scientists will make the case that the impact they are tracking occurred 3.26 billion years ago at the end of the Late Heavy Bombardment, a period between three and four billion years ago when numerous large asteroids are thought to have struck the planet....

It was just a year ago, on February 15, 2013, that the 30-meter asteroid 2012 DA14 whisked past the Earth at a distance of well less than 30,000 kilometers, inside the orbits of our geosynchronous satellites. If you don't recall 2012 DA14, it's probably because it was later on the same day that the Chelyabinsk impactor struck, a 20-meter asteroid that released the energy of approximately 460 kilotons of TNT. Chelyabinsk made it into 2014 Olympic news at Sochi, with ten gold medals for February 15 winners being embedded with fragments from the object. Today we get the passage of near-Earth asteroid 2000 EM26, whose closest approach will be covered by the Slooh network of automated telescopes starting at 2100 EST (0200 UTC), live from the Canary Islands. An iPad app is available or you can watch on Slooh.com, with the live image stream accompanied by commentary from astronomer Bob Berman and guests discussing the event and fielding questions from viewers using the hashtag #asteroid....

The same issue of Nature that carried Ian Crossfield's weather map of Luhman 16B, published yesterday, also featured a paper from Francesca DeMeo on planetary systems in chaos. Specifically, DeMeo (a Hubble postdoctoral fellow at the Harvard-Smithsonian Center for Astrophysics), looks at main belt asteroids in terms of their composition and history. Her findings reveal an early system nothing like the relatively sedate situation we see today, with small, rocky worlds near to the Sun and gas giants on much more distant orbits. Indeed, the migration of giant planets produced what DeMeo likens to "flakes in a snow globe" as asteroids were disrupted and interplanetary debris was thrown into new trajectories. The dynamical processes thus unleashed may have played a huge role in Earth's development. Working with data from the Sloan Digital Sky Survey, DeMeo teamed with Benoit Carry (Paris Observatory) to chart more than 100,000 asteroids throughout the Solar System, finding that especially...

Just over 8300 people have now signed the petition supporting the New Horizons Message Initiative. The approach of the 10,000 figure reminds me to jog those who haven't to stop by the site to sign the petition. For those not yet aware of the NHMI, the idea is to upload a crowdsourced package of images and data to the New Horizons spacecraft once it has completed its science mission at Pluto/Charon and any Kuiper Belt Object within range. Jon Lomberg's team calls the NHMI a 'Voyager Golden Record 2.0,' a worthy goal indeed, and I'll also mention that the names of the first 10,000 signing the petition will be uploaded along with the images and data. For me, one of the most interesting aspects of the initiative will be to see how the crowdsourcing project works to determine both the form and the content of the message. New Horizons' principal investigator Alan Stern has signed off on the idea, saying "I think it will inspire and engage people to think about SETI and New Horizons in new...

The Pan-STARRS survey telescope in Hawaii has reminded us how much we still have to learn about asteroids. We saw yesterday that the Chelyabinsk impactor could be studied through physical evidence as well as the ample photographic records made by witnesses on the ground. But P/2013 P5, discovered by Pan-STARRS and then the object of Hubble scrutiny, is in the main belt between Mars and Jupiter, and rather than appearing as a mere point source, the object shows six comet-like tails that have confounded all those who have looked at it. "It's hard to believe we're looking at an asteroid," said lead investigator David Jewitt, a professor in the UCLA Department of Earth and Space Sciences and the UCLA Department of Physics and Astronomy. "We were dumbfounded when we saw it. Amazingly, its tail structures change dramatically in just 13 days as it belches out dust." Image: This NASA Hubble Space Telescope set of images reveals a never-before-seen set of six comet-like tails radiating from a...

We’re still trying to learn how frequently asteroid events like the spectacular fireball over Chelyabinsk occur. The Chelyabinsk object was the largest to fall to Earth since the Tunguska explosion in 1908, which leveled thousands of acres of forest in Siberia. This BBC story discusses Peter Brown (University of Western Ontario) and colleagues’ recent paper in Nature and goes on to quote Brown as saying that a few days’ to a week’s warning would have been valuable so that we would have been prepared for what happened near the Siberian city. True enough, but what’s significant here is that the Brown team studied 20 years of data from sensors positioned around the world to estimate the frequency of such events. The upshot: About sixty asteroids up to 20 meters in size entered Earth’s atmosphere during this period, a significantly higher number than was previously assumed. Brown’s team reports we’ve been underestimating the strike rate of asteroids between 10 and 20 meters in size by...

Voyager 1 is now an interstellar spacecraft, according to the latest reports (and I'll have thoughts on Voyager, its progress and its implications, on Monday). For today, though, Keith Cooper is envisioning other ways of going interstellar, methods that take advantage of natural objects like comets. Can we harness their resources and change the paradigm of deep space flight? Keith has written often for Centauri Dreams despite a busy schedule as editor of the British monthly Astronomy Now and equivalent duties at Principium, the newsletter of the Institute for Interstellar Studies. This look at how we might expand into the Oort Cloud and beyond takes us into a future in which our species may well differentiate as we explore different ways of reaching the stars. by Keith Cooper Amidst the clamor for giant metal-hulled ships, fusion engines and warp drive, our interstellar pioneers may be missing a trick. Why go to all the trouble of building a starship when there are trillions of...

When we study extrasolar planetary systems, we're seeing stars and planets in a wide variety of ages and configurations, helpful in making sense out of our own system's past. New work out of the University of Antioquia (Medellin, Colombia) suggests changes to the main belt of asteroids between Mars and Jupiter of a kind that we may one day be able to spot in the disks around stars younger than the Sun. What Ignacio Ferrin and team have found is that the main belt, already known to house more than a million objects from one meter to 950 kilometers in size, is also what their paper calls "an enormous graveyard of ancient dormant and extinct rocky comets." That conclusion emerges from a study of main belt asteroids recently discovered to have cometary characteristics (the paper calls these 'asteroidal belt comets', or ABCs). These objects sublimate ices and otherwise behave like comets even though their orbits are entirely asteroidal. The researchers believe that what we are seeing is...

Although we have little observational data to go on, the existence of the Oort Cloud simply makes sense. We see new comets coming into the inner system that are breaking up as they approach the Sun, obviously not candidates for long survival. There has to be a source containing billions of comets to account for those we do see. The Kuiper Belt is stuffed with what we can call 'iceteroids,' all moving more or less along the plane of the ecliptic until, well beyond the Kuiper Belt itself at about 10,000 AU, the disk shaped belt of material spreads into the spherical Oort Cloud. A nudge from a rogue planet or passing star is enough to produce the velocity change to send a comet inward. We've been looking this week at possible human uses for cometary objects, including the fact that they're rich in water but also nitrogen and carbon wrapped up in interesting organic compounds. From the standpoint of resource extraction, we also find interesting elements like silicon, sulfur, nickel,...

It's hard to imagine a sane human being who would choose to live in the Oort Cloud, on a colony world where the outside temperature is in the single digits Kelvin and small bands of maybe 25 each would tend to the problems of energy production and resource extraction. Human contact beyond this would be sporadic, though Richard Terra makes the case (in "Islands in the Sky," an Analog article I referenced yesterday) that a larger community dispersed through nearby settlements would meet regularly to ensure genetic diversity and relieve isolation. History tells us that people do all kinds of inexplicable things, and perhaps a small number of adventurers, outcasts, zealots and other dissidents would find a home here. But given the abundant resources closer to the inner system, I'm more inclined to look at the Oort Cloud as a source of raw materials for colonies on the move between stars. These would be generation ships moving perhaps no faster than Voyager 1 moves now, about 17...

We can hope that the celestial events of February 15, including the spectacular fireball over Chelyabinsk and the near-miss from asteroid 2012 DA14, have raised public consciousness about Earth's neighbors in space. And indeed, this seems to be the case. Media outlets were flooded with articles, photos and video, and talk show hosts found themselves asking what could be done to prevent future impacts. Could all of this prompt a new surge of interest in space? The scenario is exactly what Arthur C. Clarke wrote about in Rendezvous with Rama (1972), where what it takes for humanity to get serious about developing a protective system (and, by extension, about pushing its space program forward) is an impact. We can be grateful that the one we've just seen was far smaller than Clarke's, as described in the first chapter of the novel: At 0946 GMT on the morning of September 11 in the exceptionally beautiful summer of the year 2077, most of the inhabitants of Europe saw a dazzling fireball...

Deep Space Industries is announcing today that it will be engaged in asteroid prospecting through a fleet of small 'Firefly' spacecraft based on cubesat technologies, cutting the costs still further by launching in combination with communications satellites. The idea is to explore the small asteroids that come close to Earth, which exist in large numbers indeed. JPL analysts have concluded that as many as 100,000 Near Earth Objects larger than the Tunguska impactor (some 30 meters wide) are to be found, with roughly 7000 identified so far. So there's no shortage of targets (see Greg Matloff's Deflecting Asteroids in IEEE Spectrum for more on this. 'Smaller, cheaper, faster' is a one-time NASA mantra that DSI is now resurrecting through its Firefly spacecraft, each of which masses about 25 kilograms and takes advantages of advances in computing and miniaturization. In its initial announcement, company chairman Rick Tumlinson talked about a production line of Fireflies ready for action...

Let's talk this morning about the 'snow line,' the boundary in the Solar System beyond which volatiles like water ice remain cold enough to keep intact. Rebecca Martin (University of Colorado) and Mario Livio (Space Telescope Science Institute) have been running simulations using models of planet-forming disks around young stars. The idea: To calculate the location of the snow line in these disks as measured against the mass of the central star. Their hypothesis is that asteroid belts in other solar systems will be located at the snow line, with implications for life. Here's the thinking on this. We know that asteroids, in addition to creating impact threats that can trigger world-changing events, may also have had a crucial role delivering water and organic compounds to the early Earth. Occasional asteroid impacts, says the theory of punctuated equilibrium, may have accelerated biological evolution, forcing species to adapt to rapidly changing conditions. And there are still other...

Planetary Resources has us thinking about mining the asteroids to extract useful materials, but learning more about these objects will benefit us in all kinds of ways. Not only do asteroids offer up clues about the early Solar System, but getting to understand their composition and structure will be a key element in any future plans to change an asteroid trajectory. The topic comes to mind periodically as various asteroids make close approaches, and right now I'm looking at asteroid 2012 DA14, which will close to within 22,000 kilometers this coming February. 2012 DA14 is a small asteroid, discovered in early 2012 at the Observatorio Astronómico de La Sagra in Spain, and it is not an impact threat for us next year, although prudence dictates keeping an eye on it for future orbits -- the object is recently enough discovered that we'll need to study it longer to get a better read on future encounters. I see that the University of Central Florida is organizing a viewing party in...

About a year ago a French couple by the name of Comette returned to their home to find that a meteorite had struck their house while they were away on holiday. It could be said that the Comettes already had a celestial connection -- if in name only -- but now the heavens impinged upon their lives again, a fact they didn't realize until their roof began to leak. Living in Draveil, about 12 miles south of Paris, the couple discovered that the space rock had blown right through a thick tile and wedged itself in glass wool insulation. It turns out to be an iron-rich chondrite some 4.57 billion years old. France, according to this article in The Telegraph, receives the highest number of meteorites per capita in the world, and the Comettes have no intention of parting with this one. The story reminded me of 14-year old Gerrit Blank, who was hit on the hand by a red-hot piece of rock about the size of a pea that went on to create a foot-wide crater in the ground. This was back in 2009 in...

Asteroids are certainly having their moment in the press, what with the combined attention being paid first to Planetary Resources and its plans for asteroid mining, and now the B612 Foundation, with a plan that in some ways tracks the Planetary Resources model. As announced yesterday, B612 intends to build a space telescope using private funding and launch it into a Solar orbit, from which it can carry out discovery and mapping operations targeting asteroids that might pose a threat to the Earth. You'll recall that Planetary Resources also has an ambitious agenda in terms of developing a series of small space telescopes. NASA, it's true, is already searching for Earth-crossing asteroids, and between ground-based efforts and space-borne missions like the Wide-Field Infrared Survey Explorer, thousands of asteroids that pass near the Earth have been discovered. But what the B612 Foundation is calling Sentinel will be dedicated to finding the smaller objects whose effect could still be...

We know that the early Earth was a violent place, but just how violent? The so-called Late Heavy Bombardment is thought to have occurred from 4.1 billion to 3.8 billion years ago, likely the result of asteroids being destabilized in their orbits by shifts in the orbits of the outer planets. That model is self-limiting, with the unstable asteroids being depleted over time and the Late Heavy Bombardment winding down, and it matches the dating of rocks from the lunar basins that show vivid evidence of the battering both Earth and Moon took. But as I mentioned last week, the question of the length of the Late Heavy Bombardment is in play, with two papers in Nature suggesting that heavy impacts may have continued for a much longer time, perhaps half of the Earth's history. William Bottke (Southwest Research Institute) and team are suggesting that during this early period, the inner edge of the asteroid belt was just 1.7 AU from the Sun -- in a region called the E-belt, a largely extinct...

Still catching up after the recent series on antimatter propulsion, I want to move into some intriguing work on panspermia, the idea that life may spread throughout a Solar System, and perhaps from star to star, because of massive impacts on a planetary surface. Catching up with older stories means leaving some things unsaid about antimatter -- in particular, I want to return to the question of antimatter storage, which in my mind is far more significant a problem even than antimatter production. But there's time for that next week, and as I said yesterday, interesting stories keep accumulating and deserve our attention. Planetary Ejecta and Trapped Microorganisms What Tetsuya Hara (Kyoto Sangyo University) and colleagues put forth in a recent paper are their calculations about the ejection of life-bearing rocks and water into space from events like the possible 'dinosaur killer' asteroid impact some 65 million years ago, which involved an asteroid 10 kilometers in diameter. It's a...

As we continue to think about the implications of Planetary Resources and its plans for asteroid mining, I was interested to see exoplanet hunter Sara Seager (MIT) make a rousing case for the company's ideas and for commercial space ventures in general. Seager, who works with Planetary Resources as a science advisor, tells The Atlantic's Ross Andersen in a May 14 interview that one reason for optimism is the progress we're making with robotics. Mining operations currently being managed beneath the seas are being handled by robotics. Couple that with our ability to get to and orbit an asteroid as well as to scoop up surface materials and you have all the ingredients for a workable mining operation in a low-gravity environment. Seager explains that asteroids are attractive mining targets because unlike fully formed planets like the Earth, their heavier elements have not largely sunk inside through planetary differentiation in the early days of the planet's existence. Asteroids are...

One of the topics receiving fairly little coverage in the excitement of the Planetary Resources announcement is asteroid deflection. It seems clear that learning how to reach an asteroid and extract everything from water to platinum-group metals from it will also teach us strategies for changing an asteroid's trajectory, in the event we find one likely to hit the Earth. The recent report from the Keck Institute of Space Studies makes this point clearly in the context of its own mission study, a plan to retrieve a small (7 m) asteroid and park it in lunar orbit. What Asteroid Operations Can Teach Us Although Planetary Resources estimates there are more than 1500 asteroids that are as easy to get to as the Moon, we still have a long way to go in understanding basic facts about these objects and their composition. Take dust, which will probably vary from object to object, but which could cause problems for 'gravity tractor' concepts where a spacecraft is used to deflect an asteroid...