Giant impact formed asteroid Vesta's Rheasilvia basin

A high-speed camera recorded a laboratory simulation of colliding heavenly bodies. 

An analysis of shock propagation suggests what may have caused the tilted canyon-like grooves around the equator of the asteroid Vesta. 

Credit: Angela Stickle and Peter Schultz

When NASA's Dawn spacecraft visited the asteroid Vesta in 2011, it showed that deep grooves that circle the asteroid's equator like a cosmic belt were probably caused by a massive impact on Vesta's south pole.

Now, using a super high-speed cannon at NASA's Ames Research Center, Brown

University researchers have shed new light on the violent chain of events deep in Vesta's interior that formed those surface grooves, some of which are wider than the Grand Canyon.

"Vesta got hammered," said Peter Schultz, professor of earth, environmental, and planetary sciences at Brown and the paper's senior author.

"The whole interior was reverberating, and what we see on the surface is the manifestation of what happened in the interior."

The research suggests that the Rheasilvia basin on Vesta's south pole was created by an impactor that came in at an angle, rather than straight on, but that glancing blow still did an almost unimaginable amount of damage.

The study shows that just seconds after the collision, rocks deep inside the asteroid began to crack and crumble under the stress.

Within two minutes major faults reached near the surface, forming deep the canyons seen today near Vesta's equator, far from the impact point.

The research, led by Angela Stickle, a former graduate student at Brown and now a researcher at the Johns Hopkins University Applied Physics Laboratory, will appear in the February issue of the journal Icarus and is now available online.

"As soon as Pete and I saw the images coming down from the Dawn mission at Vesta, we were really excited," Stickle said.

"The large fractures looked just like things we saw in our experiments. So we decided to look into them in more detail, and run the models, and we found really interesting relationships."


For the study, the researchers used the Ames Vertical Gun Range, a cannon with a 14-foot barrel used to simulate collisions on celestial bodies.

The gun uses gunpowder and compressed hydrogen gas to launch projectiles at blinding speed, up to 16,000 miles per hour.

For this latest research, Schultz and his colleagues launched small projectiles at softball-sized spheres made of an acrylic material called PMMA.

When struck, the normally clear material turns opaque at points of high stress. By watching the impact with high-speed cameras that take a million shots per second, the researchers can see how these stresses propagate through the material.



The experiments showed that that damage from the impact starts where one would expect: at the impact point, but shortly after, failure patterns begin to form inside the sphere, opposite the point of impact.

Those failures grow inward toward the sphere's center and then propagate outward toward the edges of the sphere like a blooming flower.

Using numerical models to scale the lab collision up to the size of Vesta, the second-largest object in the asteroid belt, the researchers showed that the outward-blooming "rosette" of damage extending to the surface is responsible for the troughs that form a belt around Vesta's equator.

The results answer some questions about Vesta's belt that had long been puzzling. Chief among them is the orientation of the belt with respect to the crater.

The belt's angle isn't exactly what would be expected if it were caused by the Rheasilvia impact.

"The belt is askew," Schultz said, "as if Vesta were making a fashion statement."

These new experiments suggest that the crooked belt is the result of the angle of impact. An oblique impact causes the damage plane to be tilted with respect the crater.

The orientation of Vesta's belt sheds light on the nature of the impact. The researchers conclude that the object that created Rheasilvia came in at an angle less than 40 degrees, traveling at about 11,000 miles per hour.

"Vesta was lucky," Schultz said. "If this collision had been straight on, there would have been one less large asteroid and only a family of fragments left behind."

The research shows that even a glancing blow can have tremendous consequences.
"When big things happen to small bodies," Schultz said, "it shakes them to the core."

ESA Rosetta - Lutetia's Lineaments: Dark side of asteroid hosts hidden crater

ESA's Rosetta spacecraft data. Tracing Lutetia’s grooves.

Credit: ESA /Rosetta /MPS for OSIRIS Team MPS /UPD /LAM /IAA /SSO /INTA /UPM /DASP /IDA

Grooves found on Lutetia, an asteroid encountered by ESA's Rosetta spacecraft, point to the existence of a large impact crater on the unseen side of the rocky world.

ESA's Rosetta spacecraft flew past Lutetia at a distance of 3168 km in July 2010, en route to its 2014 rendezvous with its target comet.

The spacecraft took images of the 100 km-wide asteroid for about two hours during the flyby, revealing numerous impact craters and hundreds of grooves all over the surface.

Impact craters are commonly seen on all Solar System worlds with solid surfaces, recording an intense history of collisions between bodies. However, grooves are much less prevalent.

To date, they have been discovered by visiting spacecraft only on the Martian moon Phobos and the asteroids Eros and Vesta.

The way in which grooves are formed on these bodies is still widely debated, but it likely involves impacts.

Shock waves from the impact travel through the interior of a small, porous body and fracture the surface to form the grooves.

"For Lutetia, by assuming that the grooves were formed in concentric patterns around their source impact crater, we identified 200 such features falling into distinct 'families', correlated with three different impact craters," describes Sebastien Besse, a research fellow at ESA's Technical Centre, ESTEC, in the Netherlands, and lead author of the paper published in Planetary and Space Science this month.

One of the groove systems on Lutetia is associated with the Massilia crater and another with the North Pole Crater Cluster, which comprises a number of superimposed craters. Both are on the asteroid's northern hemisphere.

This anaglyph 3D image of Lutetia can be viewed using stereoscopic glasses with red–green or red–blue filters. 

The two images making up this image were taken several minutes before Rosetta’s closest approach to the asteroid on 10 July 2010. 

The left-eye view was captured at 15:41:39 GMT from a distance of 4274 km from Lutetia’s surface and the right-eye view at 15:41:03 GMT from 4038 km (closest approach was at 15:45 GMT). 

Credit: ESA/H. Sierks (MPS, Göttingen, Germany)

But another group of grooves points to a crater not seen during Rosetta's brief flyby, in the asteroid's southern hemisphere.

Its implied presence has earned it the nickname 'Suspicio'. The grooves related to Suspicio cover a large area on the asteroid, suggesting it may span several tens of kilometres .

By comparison, Massilia, the largest known crater on Lutetia, is about 55 km wide, and the largest of the polar cluster is about 34 km across.

"These three major impacts seriously deformed Lutetia's surface," adds Sebastien.

Looking face on at the North Pole Crater Cluster (purple outline) on asteroid Lutetia, with Massilia crater to the lower left (red outline). 

Marked on the image are the concentric grooves or ‘lineaments’ associated with the large craters. 

The lineaments coloured blue infer the presence of a large crater, nicknamed Suspicio, on the unseen portion of Lutetia. 

Yellow denotes lineaments not associated with any of the craters discussed in this study. 

Credit: ESA /Rosetta /MPS for OSIRIS Team MPS /UPD /LAM /IAA /SSO /INTA /UPM /DASP /IDA

"As with grooves seen on other asteroids that may also be associated with impact events, this study provides new insights into the catastrophic history of these small bodies."

By observing how subsequent small craters lie over the grooves on Lutetia, the scientists determined the relative ages of the three larger cratering events.

Massilia is thought be the oldest of the three craters and the polar cluster the youngest, with Suspicio between.

The authors also looked at other, independent measurements of Lutetia, including ground-based observations with the Infrared Telescope Facility and space-based observations with ESA's Herschel and NASA's Spitzer.

The infra-red location of Suspicio crater on the unseen southern hemisphere of asteroid Lutetia (marked in blue). 

The hidden crater could be up to 45 km in diameter, the blue outlines correspond to diameter estimates of 15, 30 and 45 km, respectively. 

The crater is inferred based on the numerous grooves or ‘lineaments’ seen concentric to the crater in the northern hemisphere of the asteroid. 

There are no image data available for this side of the asteroid, as can be inferred from the blank shape model. 

Credit: ESA /Rosetta /MPS for OSIRIS Team MPS /UPD /LAM /IAA /SSO /INTA /UPM /DASP /IDA

The Infrared Telescope Facility suggested different compositions between the northern and southern hemisphere of the asteroid.

Sebastien and his colleagues propose that a large impact, presumably the one forming Suspicio, excavated enough material of a different composition to account for the observed differences.

"Our study ties together several independent analyses of Lutetia into one coherent story that is consistent with the presence of a large impact crater on the far side of the asteroid," says co-author Michael Küppers, from ESA's Space Astronomy Centre in Spain.

"Four years on and we are delighted still to be learning from just two hours' worth of data collected during the Lutetia flyby," says Matt Taylor, ESA's Rosetta project scientist.

"Rosetta is now in its main mission phase at its comet, where we are on the cusp of fantastic results. Rosetta is a true small bodies mission, two asteroids and one comet in single trip."

More information: S. Besse, M. Küppers, O.S. Barnouin, N. Thomas, J. Benkhoff, "Lutetia׳s lineaments," Planetary and Space Science, Volume 101, 15 October 2014, Pages 186-195, ISSN 0032-0633, dx.doi.org/10.1016/j.pss.2014.07.007

NASA DAWN: Spacecraft operating normally after safe mode triggered

Artist concept of NASA's Dawn spacecraft orbiting Ceres during an upcoming flyby. 

Credit: NASA/JPL-Caltech/UCLA

The Dawn spacecraft has resumed normal ion thrusting after the thrusting unexpectedly stopped and the spacecraft entered safe mode on September 11.

That anomaly occurred shortly before a planned communication with NASA's Deep Space Network that morning.

The spacecraft was not performing any special activities at the time.

Engineers immediately began working to restore the spacecraft to its normal operational state.

The team determined the source of the problems, corrected them, and then resumed normal ion thrusting on Monday night, Sept. 15.

"This anomaly presented the team with an intricate and elaborate puzzle to solve," said Robert Mase, Dawn project manager at NASA's Jet Propulsion Laboratory in Pasadena, California.

After investigating what caused the spacecraft to enter safe mode, the Dawn team determined that it was likely triggered by the same phenomenon that affected Dawn three years ago on approach to the protoplanet Vesta: An electrical component in the ion propulsion system was disabled by a high-energy particle of radiation.

"We followed the same strategy that we implemented three years ago to recover from a similar radiation strike, to swap to one of the other ion engines and a different electronic controller so we could resume thrusting quickly," said Dawn Mission Director and Chief Engineer Marc Rayman of JPL.

"We have a plan in place to revive this disabled component later this year."

Complicating the issue, the team discovered that the spacecraft had experienced not just one anomaly, but also a second one that affected the ability to point the main antenna at Earth to communicate.

Because the spacecraft could not communicate using its main antenna, the team had to utilize the weaker signals of another antenna, slowing their progress.

In addition, Dawn is so far from Earth that radio signals take 53 minutes to make the round trip.

Although they have not yet specifically pinpointed the cause of this issue, it could also be explained by a high-energy particle corrupting the software running in the main computer.

Ultimately the team reset the computer, which restored the pointing performance to normal.

As a result of the change in the thrust plan, Dawn will enter into orbit around dwarf planet Ceres in April 2015, about a month later than previously planned.

Ceres

The plans for exploring Ceres once the spacecraft is in orbit, however, are not affected.

Vesta

Dawn orbited Vesta, the second most massive object in the main asteroid belt, from July 2011 until September 2012.

The spacecraft's ion propulsion system enabled it to spiral away from Vesta and head toward Ceres, the most massive object in that region.

ESA's Space Situational Awareness (SSA): Bug Eyed Telescope

The SSA-NEO system is based on syndicating and federating observation and tracking data provided by a large number of European and international sources. 

Credit: ESA - P.Carril

Spotting Earth-threatening asteroids is tough partly because the sky is so big but insects offer an answer, since they figured out long ago how to look in many directions at once.

As part of the global effort to hunt out risky celestial objects such as asteroids and comets, ESA is developing an automated telescope for nightly sky surveys.

This telescope is the first in a future network that would completely scan the sky and automatically identify possible new near-Earth objects, or NEOs, for follow up and later checking by human researchers.

But a web of traditional telescopes would be complex and expensive because of the number required.

Adding to the problem, the system must be able to discover objects many times fainter than the naked eye can perceive.

While no network can spot all potentially hazardous objects, under favourable conditions it should detect everything down to about 40 m in diameter at least three weeks before impact.

The answer is a new, European telescope nicknamed 'fly-eye' that splits the image into 16 smaller subimages to expand the field of view, similar to the technique exploited by a fly's compound eye.

The design is modular, and allows for mass and cheaper production and lower maintenance costs. It will be used to build the prototype, to be fielded by ESA's Space Situational Awareness (SSA) programme early next year.

"This novel technology is key to the future NEO survey network," says Gian Maria Pinna of the SSA office.

A new, European telescope nicknamed ‘fly-eye’ splits the image into 16 smaller subimages to expand the field of view, similar to the technique exploited by a fly’s compound eye. 

Such fly-eyed survey telescopes provide a very large field of view: 6.7° x 6.7° or about 45 square degrees. 6.7° is about 13 times the diameter of the Moon as seen from the Earth (roughly 0.5 degrees). 

Credit: ESA/Compagnia Generale dello Spazio CGS

Performance equivalent to large telescope

These fly-eyed survey telescopes offer performance equivalent to a 1 m-diameter telescope, and provide a very large field of view: 6.7° x 6.7° or about 45 square degrees; 6.7° is about 13 times the diameter of the Moon as seen from the Earth.

"The new telescopes would provide the resolution necessary to determine the orbits of any detected objects," says Gian Maria.

"If the prototype confirms the expected performance, it will pave the way to full procurement and deployment of the operational network of telescopes."


Future telescope in operation. Credit: Compagnia Generale dello Spazio – CGS

This summer, ESA signed a contract for about €1 million with a consortium led by CGS S.p.A (Italy), comprising Creotech Instruments S.A. (Poland), SC EnviroScopY SRL (Romania) and Pro Optica S.A. (Romania) for the detailed design of the advanced telescope.

It is expected that the detailed design will be followed by several additional contracts with European companies valued at up to €10 million for building and deploying the first survey prototype telescope.

"The development of the first optical sensor specific to ESA's NEO search and discovery activities is a fundamental step toward Europe's contribution to safeguarding our planet from possible collisions by dangerous objects," notes Nicolas Bobrinsky, Head of the SSA Programme.

Cohesive Forces that hold gravity-defying near-earth asteroid together revealed

An asteroid 1950 DA. Credit: NASA

Researchers at the University of Tennessee, Knoxville, have made a novel discovery that may potentially protect the world from future collisions with asteroids.

The team studied near-Earth asteroid 1950 DA and discovered that the body, which rotates so quickly it defies gravity, is held together by cohesive forces called van der Waals, never detected before on an asteroid.

The findings, published in this week's edition of the science journal Nature, have potential implications for defending our planet from a massive asteroid impact.

Previous research has shown that asteroids are loose piles of rubble held together by gravity and friction. However, the UT team found that 1950 DA is spinning so quickly that it defies these forces.

Ben Rozitis, a postdoctoral researcher; Eric MacLennan, a doctoral candidate; and Joshua Emery, an assistant professor in the Department of Earth and Planetary Sciences, wanted to know what keeps the body from breaking apart.

Looking at thermal images and orbital drift to calculate thermal inertia and bulk density, the team detected the action of cohesive forces in an environment with little gravity.

"We found that 1950 DA is rotating faster than the breakup limit for its density," said Rozitis. "So if just gravity were holding this rubble pile together, as is generally assumed, it would fly apart. Therefore, interparticle cohesive forces must be holding it together."

In fact, the rotation is so fast that at its equator, 1950 DA effectively experiences negative gravity. If an astronaut were to attempt to stand on this surface, he or she would fly off into space unless he or she were somehow anchored.

The presence of cohesive forces has been predicted in small asteroids, but definitive evidence has never been seen before.

The finding provides important information for efforts aimed at stopping an asteroid from crashing into Earth.

"Following the February 2013 asteroid impact in Chelyabinsk, Russia, there is renewed interest in figuring out how to deal with the potential hazard of an asteroid impact," said Rozitis.

"Understanding what holds these asteroids together can inform strategies to guard against future impacts."

This research reveals some potential techniques, such as a kinetic impactor which would deploy a massive object on a collision course with the asteroid, could exacerbate the impact's effects.

For example, this technique could destabilize the cohesive forces keeping the asteroid together, causing it to break apart into several threatening asteroids headed for Earth.

This may be what occurred with the asteroid P/2013 R3, which was caught by the Hubble Space Telescope in 2013 and 2014 coming undone, possibly due to a collision with a meteor.

"With such tenuous cohesive forces holding one of these asteroids together, a very small impulse may result in a complete disruption," said Rozitis.

The researchers' findings also have implications for space exploration. For example, the European Space Agency's Rosetta spacecraft landed on Comet 67P/Churyumov-Gerasimenko's surface last week and it may find a dusty surface dominated by such cohesive forces.

More information: Cohesive forces prevent the rotational breakup of rubble-pile asteroid (29075) 1950 DA, Nature, dx.doi.org/10.1038/nature13632

NASA Neowise: A comet that looked like an asteroid

Comet C/2013 UQ4 (Catalina) appeared to be a highly active comet one day past perihelion on July 7, 2014.

Credit: NASA/JPL-Caltech

Comet C/2013 UQ4 (Catalina) has been observed by NASA's Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) spacecraft just one day after passing through its closest approach to the sun.

The comet glows brightly in infrared wavelengths, with a dust tail streaking more than 62,000 miles (100,000 kilometers) across the sky.

Its spectacular activity is driven by the vapourisation of ice that has been preserved from the time of planet formation 4.5 billion years ago.

"The tail forms a faint fan as the smaller dust particles are more easily pushed away from the sun by the radiation pressure of the sunlight," said James Bauer, researcher at NASA's Jet Propulsion Laboratory in Pasadena, California.

C/2013 UQ4 takes more than 450 years to orbit the sun once and spends most of its time far away at very low temperatures.

Its orbit is also retrograde, which means that the comet moves around the sun in the opposite direction to the planets and asteroids.

The comet was originally thought to be an asteroid, as it appeared inactive when discovered by the Catalina Sky Survey on October 23, 2013.

NEOWISE also observed the comet to be inactive on New Year's Eve, 2013, but since then the comet has become highly active, allowing astronomers around the world to observe it.

The comet's activity should decline as it once again returns to the cold recesses of space.

Argon Isotope Laboratory: Nullarbor meteorite a fragment of an unknown asteroid

Full View of Asteroid Vesta

The first meteorite ever located solely using data from specially-placed cameras has been found to be geologically unique, presenting questions of its origins.

Geochronologist Fred Jourdan says the Bunburra Rockhole meteorite, found seven years ago on the WA side of the Nullarbor Plain, appears to be part of an asteroid that may no longer exist.

It consists of basalt with a character never before found in a meteorite.

"This one has a particular composition—which makes us think that it comes from a different body that has not been sampled before," Associate Professor Jourdan says.

Based on present scientific knowledge, he says most basalt meteorites are thought to have originated from volcanic eruptions on the asteroid Vesta, that NASA's Dawn spacecraft spent a year orbiting.

Vesta is the solar system's second-largest asteroid, more than 500km wide, that had a magmatic eruption at the beginning of its history 4.5 billion years ago, exhausting its heat.

This meteorite was unknown asteroid
However A/Prof Jourdan says a giant impact may have destroyed another, previously unknown asteroid about 3.6 billion years ago.

The Bunburra Rockhole meteorite is thought to be a fragment of this former asteroid.

The impact generated tremendous heat that "reset" the rock's isotopic signature.

"There's no way, with our knowledge of the current laws of physics, that we would have vulcanism at this time because all the heat is long gone from the asteroids," he says.

"It [the unknown asteroid] was born 4.5 – 6 billion years ago and then it probably got shattered 3.6 billion years ago."

He says this occurred at a time when asteroid bombardments were common—most appear to have happened between 3.8 and 3.3 billion years ago.

Argon dating back in time
Prof Jourdan is director of Curtin University's Argon Isotope Laboratory, a facility the team used to date the Bunburra Rockhole meteorite using the "argon-argon" method.

"Potassium decays in Argon and with that we can measure the age of a given geological event," he says.

"By measuring Argon 39 and Argon 40 we can back calculate major events.

"We take a chunk of rock, we separate the different crystals if we can, if it's too small we take bulk rock, and we put them under a Laser.

"The Laser heats the grain and releases the argon, and the argon is measured on a mass spectrometer."

He says finding part of a "new" asteroid helps confirm existing knowledge of the solar system's bombardment history by increasing the sample size, which has been biased by most available specimens coming from the asteroid Vesta.

More information: 40Ar/39Ar impact ages and time–temperature argon diffusion history of the Bunburra Rockhole anomalous basaltic achondrite,Geochimica et Cosmochimica Acta, Volume 140, 1 September 2014, Pages 391–409 www.sciencedirect.com/science/… ii/S001670371400386X

NASA NEOWISE: Asteroid 2014 HQ124 to Pass Earth Safely

This diagram shows the orbit of asteroid 2014 HQ124, and its location relative to Earth on June 8.

Image Credit: NASA/JPL-Caltech

A newfound asteroid will safely pass Earth on June 8 from a distance of about 777,000 miles (1.25 million kilometers), more than three times farther away than our moon.

Designated 2014 HQ124, the asteroid was discovered April 23, 2014, by NASA's NEOWISE mission, a space telescope adapted for scouting the skies for asteroids and comets.

The telescope sees infrared light, which allows it to pick up the infrared glow of asteroids and obtain better estimates of their true sizes.

The NEOWISE data estimate asteroid 2014 HQ124 to be between 800 and 1,300 feet (250 and 400 meters).

More than one hundred follow-up observations from NASA-funded, ground-based telescopes and amateur astronomers were used to pin down the orbit of the asteroid out to the year 2200, during which time it poses no risk to Earth.

Its trajectory will continue to be recalculated past that time frame as additional observations are received.

"There is zero chance of an impact," said Don Yeomans, manager of NASA's Near-Earth Object Program Office at NASA's Jet Propulsion Laboratory in Pasadena, California.

"In fact, it's fairly common for asteroids to pass near Earth. You'd expect an object about the size of 2014 HQ124 to pass this close every few years."

Yeomans said that 2014 HQ124 is a good target for radar observations using NASA's Deep Space Network antenna at Goldstone, California, and the Arecibo Observatory in Puerto Rico, shortly after the closest approach on June 8.

Radar measurements of asteroid distances and velocities often enable computation of asteroid orbits much further into the future than otherwise known.

2014 HQ124 is designated a "potentially hazardous asteroid," or PHA, which refers to those asteroids 460 feet (140 meters) in size or larger that pass within 4.6 million miles (7.4 million kilometers) of Earth's orbit around the sun.

There are currently 1,484 known PHAs, but none pose a significant near-term risk of impacting Earth.

"Because NEOWISE is a space telescope observing the dawn and twilight sky at infrared wavelengths, it is particularly good at finding large NEOs that make relatively close passes to Earth," said Amy Mainzer, the principal investigator of NEOWISE at JPL.

"Using infrared light, we can estimate the object’s size, and we can tell that it reflects a fair amount of light. That means it’s most likely a stony object.”

NASA detects, tracks and characterizes asteroids and comets passing close to Earth using both ground- and space-based telescopes.

The Near-Earth Object Program, commonly called "Spaceguard," discovers these objects, characterizes a subset of them and identifies their orbits to determine if any could be potentially hazardous to our planet.

To date, U.S. assets have discovered more than 98 percent of the known near-Earth objects.

Asteroid and Comet Impacts: Impact glass stores biodata for millions of years

The scorching heat produced by asteroid or comet impacts can melt tons of soil and rock, some of which forms glass as it cools. 

Some of that glass preserves bits of ancient plant material. 

Credit: Brown University

Bits of plant life encapsulated in molten glass by asteroid and comet impacts millions of years ago give geologists information about climate and life forms on the ancient Earth.

Scientists exploring large fields of impact glass in Argentina suggest that what happened on Earth might well have happened on Mars millions of years ago. Martian impact glass could hold traces of organic compounds.

Asteroid and comet impacts can cause widespread ecological havoc, killing off plants and animals on regional or even global scales.

But new research from Brown University shows that impacts can also preserve the signatures of ancient life at the time of an impact.

A research team led by Brown geologist Pete Schultz has found fragments of leaves and preserved organic compounds lodged inside glass created by a several ancient impacts in Argentina.

The material could provide a snapshot of environmental conditions at the time of those impacts. The find also suggests that impact glasses could be a good place to look for signs of ancient life on Mars.

The work is published in the latest issue of Geology magazine.

The scorching heat produced by asteroid or comet impacts can melt tons of soil and rock, some of which forms glass as it cools.

The soil of eastern Argentina, south of Buenos Aires, is rife with impact glass created by at least seven different impacts that occurred between 6,000 and 9 million years ago, according to Schultz.

One of those impacts, dated to around 3 million years ago, coincides with the disappearance of 35 animal genera, as reported in the journal Science a few years back.

"We know these were major impacts because of how far the glass is distributed and how big the chunks are," Schultz said.

"These glasses are present in different layers of sediment throughout an area about the size of Texas."

Within glass associated with two of those impacts—one from 3 million years ago and one from 9 million years ago, Schultz and his colleagues found exquisitely preserved plant matter.

"These glasses preserve plant morphology from macro features all the way down to the micron scale," Schultz said. "It's really remarkable."

The glass samples contain centimeter-size leaf fragments, including intact structures like papillae, tiny bumps that line leaf surfaces.

Bundles of vein-like structures found in several samples are very similar to modern pampas grass, a species common to that region of Argentina.

Chemical analysis of the samples also revealed the presence of organic hydrocarbons, the chemical signatures of living matter.

"Impact glass may be where the 4 billion-year-old signs of life are hiding," Schultz said. "On Mars they're probably not going to come out screaming in the form of a plant, but we may find traces of organic compounds, which would be really exciting."

More information: Paper: geology.gsapubs.org/content/early/2014/04/14/G35343.1.abstract

Read the full article here

NASA OSIRIS-REx: Spacecraft that will visit asteroid in 2018

This is an artist's concept of NASA's OSIRIS-REx spacecraft preparing to take a sample from asteroid Bennu. 

Credit: NASA/Goddard

NASA has given the OSIRIS-REx mission, led by the University of Arizona, the go-ahead to begin building the spacecraft, flight instruments, ground system and launch support facilities.

OSIRIS-REx is the first U.S. mission slated to send a spacecraft to a near-Earth asteroid and collect samples.

The mission will focus on finding answers to basic questions about the composition of the very early solar system and the source of organic materials and water that made life possible on Earth.

It will also aid NASA's asteroid initiative and support the agency's efforts to understand the population of potentially hazardous near-Earth objects and characterize those suitable for future asteroid exploration missions.

The UA got the thumbs up on April 9 after a successful Mission Critical Design Review (CDR) for NASA's Origins Spectral Interpretation Resource Identification Security Regolith Explorer (OSIRIS-REx).

The review was held at the Lockheed Martin Space Systems Company in Littleton, Colo., April 1-9. An independent review board, comprised of experts from NASA and several external organizations, met to review the system design.

"Successfully passing mission CDR is a major accomplishment, but the hard part is still in front of us—building, integrating and testing the flight system to meet our tight launch window," said Mike Donnelly, OSIRIS-REx project manager at NASA's Goddard Space Flight Center in Greenbelt, Md.

"It marks a major shift in our mission," said Ed Beshore, a scientist at the UA Lunar and Planetary Laboratory and the Department of Astronomy and Steward Observatory, who is the mission's deputy principal investigator.

"For all of us involved with OSIRIS-REx, it is a transition from designing the mission to implementing it. It means we are now cutting metal, building a spacecraft and writing software."

OSIRIS-REx is scheduled to launch in the fall of 2016, rendezvous with the asteroid Bennu in 2018 and spend a year studying the asteroid before collecting a sample of at least 2 ounces (60 grams) of surface material and returning it to Earth for scientists to study in 2023.

NASA's Goddard Space Flight Center will provide overall mission management, systems engineering and safety and mission oversight for OSIRIS-REx. The UA will lead the effort, provide the camera system and science processing and operations center.

Lockheed Martin Space Systems in Denver will build the spacecraft. OSIRIS-REx is the third mission in NASA's New Frontiers Program, which is managed by the Marshall Spaceflight Center.

Asteroid Chariklo found to have two rings

Observations at many sites in South America, including ESO's La Silla Observatory, have made the surprise discovery that the remote asteroid Chariklo is surrounded by two dense and narrow rings. 

This is the smallest object by far found to have rings and only the fifth body in the Solar System, after the much larger planets Jupiter, Saturn, Uranus and Neptune, to have this feature. 

The origin of these rings remains a mystery, but they may be the result of a collision that created a disc of debris. 

This artist's impression shows how the rings might look from close to the surface of Chariklo. 

Credit: ESO /L. Calçada /Nick Risinger (skysurvey.org)


Observations at many sites in South America have made the discovery that the asteroid Chariklo is surrounded by two dense and narrow rings.

This is the smallest object by far found to have rings and only the fifth body in the Solar System to have this feature.

The origin of these rings remains a mystery, but they may be the result of a collision that created a disc of debris.

The rings of Saturn are one of the most spectacular sights in the sky, and less prominent rings have also been found around the other giant planets.

Despite many careful searches, no rings had been found around smaller objects orbiting the Sun in the Solar System.

Now observations of the distant minor planet (10199) Chariklo as it passed in front of a star have shown that this object too is surrounded by two fine rings.

"We weren't looking for a ring and didn't think small bodies like Chariklo had them at all, so the discovery, and the amazing amountof detail we saw in the system, came as a complete surprise!" says Felipe Braga-Ribas (Observatório Nacional/MCTI, Rio de Janeiro, Brazil) who planned the observation campaign and is lead author on the new paper.

Chariklo is the largest member of a class known as the Centaurs and it orbits between Saturn and Uranus in the outer Solar System.

Predictions had shown that it would pass in front of the star UCAC4 248-108672 on 3 June 2013, as seen from South America.

Astronomers using telescopes at seven different locations, including the 1.54-metre Danish and TRAPPIST telescopes at ESO's La Silla Observatory in Chile, were able to watch the star apparently vanish for a few seconds as its light was blocked by Chariklo—an occultation.

Chariklo is a comet-like miniature planet located between Saturn and Uranus. 

It has a diameter of 250 km and new observations show that there are two rings of ice particles and pebbles. 

This is the first time such a small celestial body with rings has been observed. 

Credit: Lucie Maquet

But they found much more than they were expecting. A few seconds before, and again a few seconds after the main occultation there were two further very short dips in the star's apparent brightness.

Something around Chariklo was blocking the light! By comparing what was seen from different sites the team could reconstruct not only the shape and size of the object itself but also the shape, width, orientation and other properties of the newly discovered rings.

The team found that the ring system consists of two sharply confined rings only seven and three kilometres wide, separated by a clear gap of nine kilometres—around a small 250-kilometre diameter object orbiting beyond Saturn.

"For me, it was quite amazing to realise that we were able not only to detect a ring system, but also pinpoint that it consists of two clearly distinct rings," adds Uffe Gråe Jørgensen (Niels Bohr Institute, University of Copenhagen, Denmark), one of the team.

"I try to imagine how it would be to stand on the surface of this icy object, small enough that a fast sports car could reach escape velocity and drive off into space, and stare up at a 20-kilometre wide ring system 1000 times closer than the Moon."

The special camera is Irish, and the software programs were specially developed over five years at the Niels Bohr Institute by three astronomers and two Ph.D. students. 

It takes 40 images per second and the resolution is just as fantastic as if it was out in space. 

It is now sitting on the Danish telescope at the La Silla Observatory in Chile. 

The main purpose of the camera is to observe exoplanets, which are planets orbiting a star other than the Sun, but the sensitive camera has also shown its strength for making extremely precise observations of other objects. 

Credit: Jesper Skottfelt, Niels Bohr Institute

Although many questions remain unanswered, astronomers think that this sort of ring is likely to be formed from debris left over after a collision. It must be confined into the two narrow rings by the presence of small putative satellites.

"So, as well as the rings, it's likely that Chariklo has at least one small moon still waiting to be discovered," adds Felipe Braga Ribas.

The rings may prove to be a phenomenon that might in turn later lead to the formation of a small moon. Such a sequence of events, on a much larger scale, may explain the birth of our own Moon in the early days of the Solar System, as well as the origin of many other satellites around planets and asteroids.

The leaders of this project are provisionally calling the rings by the nicknames Oiapoque and Chuí, two rivers near the northern and southern extremes of Brazil.

More information: Paper: dx.doi.org/10.1038/nature13155

Astronomers witness mysterious and unique disintegration of asteroid

This series of Hubble Space Telescope images reveals the breakup of an asteroid over a period of several months in late 2013. 

The largest fragments are up to 200 yards in radius, each with "tails" caused by dust lifted from their surfaces and pushed back by the pressure of sunlight. 

The 10 pieces of the asteroid drift apart slowly and show a range of breakup times, suggesting that the disintegration cannot be explained by a collision with another asteroid. 

One idea for the breakup is that the asteroid was accelerated by sunlight to spin at a fast enough rate to fly apart by centrifugal force. 

The images were taken in visible light with Hubble's Wide-Field Camera 3. 

Credit: NASA, ESA, D. Jewitt/UCLA

Astronomers have witnessed for the first time the breakup of an asteroid into as many as 10 smaller pieces.

The discovery is published online March 6 in Astrophysical Journal Letters.

Though fragile comet nuclei have been seen falling apart as they near the sun, nothing resembling this type of breakup has been observed before in the asteroid belt. NASA's Hubble Space Telescope photographed the demolition.

"Seeing this rock fall apart before our eyes is pretty amazing," said David Jewitt, a professor in the UCLA Department of Earth, Planetary and Space Sciences and the UCLA Department of Physics and Astronomy, who led the astronomical forensics investigation.

The crumbling asteroid, designated P/2013 R3, was first noticed as an anomalous, fuzzy-looking object on Sept. 15, 2013, by the Catalina and Pan-STARRS sky-survey telescopes.

Pan-STARRS sky-survey telescope

A follow-up observation on Oct. 1 with the W.M. Keck telescope on Hawaii's Mauna Kea revealed three co-moving bodies embedded in a dusty envelope that is nearly the diameter of Earth.

"The Keck telescope showed us that this asteroid was worth looking at with Hubble," Jewitt said.

With its superior resolution, the Hubble telescope revealed that there were really 10 embedded objects, each with comet-like dust tails.

The four largest rocky fragments are up to 200 yards in radius, about twice the length of a football field.

The Hubble data showed that the fragments are drifting away from each other at a leisurely pace of one mile per hour—slower than a strolling human.

The asteroid began coming apart early last year, but new pieces continue to emerge in the most recent images.

This makes it unlikely that the asteroid is disintegrating because of a collision with another asteroid, which would be instantaneous and violent.

Some of the debris from such a high-velocity smash-up would also be expected to travel much faster than observed.

Huge Peanut-Shaped Asteroid Buzzes Earth in NASA - Video

A large asteroid shaped like a cosmic peanut zipped safely by Earth this month, and a new NASA video retells the entire space rock encounter as it happened using impressive radar images.

Scientists using NASA's Deep Space Network Goldstone antenna in California tracked the near-Earth asteroid 2006 DP14 using radar imaging as the space rock passed within 2.6 million miles (4.2 million kilometers) of our planet on Feb. 12.

The new radar images show that 2006 DP14 is about 1,300 feet long (400 meters) and 660 feet wide (200 m).

NASA video of asteroid 2006 DP14's Earth flyby with the Goldstone radar images is shown above.

The asteroid is known as a "contact binary" because the two halves of its peanut shape seem to be touching and moving through space together.

2006 DP14 made its closest approach to Earth on Feb. 10 when it traveled about 1.5 million miles (2.4 million km) from the planet's surface, NASA officials said.

Scientists then observed the asteroid on Feb. 12 from 12:03 a.m. EST to 2:27 a.m. EST (0503 GMT to 0727 GMT).

"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," NASA representatives wrote in a statement.

"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."

Earlier studies have shown that about 10 percent of near-Earth asteroids larger than 650 feet (200 m) have contact binary shapes, NASA officials said.

Comets and asteroids are considered near-Earth objects (NEOs) of they fly within about 28 million miles (45 million km) of Earth's orbital distance, NASA officials have said.

ESO: The anatomy of an asteroid

This is a schematic view of the strange peanut-shaped asteroid Itokawa. 

By making exquisitely precise timing measurements using ESO's New Technology Telescope (NTT), and combining them with a model of the asteroid's surface topography, a team of astronomers has found that different parts of this asteroid have different densities. 

As well as revealing secrets about the asteroid's formation, finding out what lies below the surface of asteroids may also shed light on what happens when bodies collide in the Solar System, and provide clues about how planets form. 

The shape model used for this view is based on the images collected by JAXA's Hayabusa spacecraft. 

Credit: ESO. Acknowledgement: JAXA

ESO's New Technology Telescope (NTT) has been used to find the first evidence that asteroids can have a highly varied internal structure.

By making measurements astronomers have found that different parts of the asteroid Itokawa have different densities.

As well as revealing secrets about the asteroid's formation, finding out what lies below the surface may also shed light on what happens when bodies collide in the Solar System, and provide clues about how planets form.

Stephen Lowry

Using very precise ground-based observations, Stephen Lowry (University of Kent, UK) and colleagues have measured the speed at which the near-Earth asteroid (25143) Itokawa spins and how that spin rate is changing over time.

They have combined these delicate observations with new theoretical work on how asteroids radiate heat.

This small asteroid is an intriguing subject as it has a strange peanut shape, as revealed by the Japanese spacecraft Hayabusa in 2005.

To probe its internal structure, Lowry's team used images gathered from 2001 to 2013, by ESO's New Technology Telescope (NTT) at the La Silla Observatory in Chile among others, to measure its brightness variation as it rotates.

This timing data was then used to deduce the asteroid's spin period very accurately and determine how it is changing over time.

When combined with knowledge of the asteroid's shape this allowed them to explore its interior—revealing the complexity within its core for the first time.

"This is the first time we have ever been able to to determine what it is like inside an asteroid," explains Lowry.

"We can see that Itokawa has a highly varied structure—this finding is a significant step forward in our understanding of rocky bodies in the Solar System."

The spin of an asteroid and other small bodies in space can be affected by sunlight. This phenomenon, known as the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect, occurs when absorbed light from the Sun is re-emitted from the surface of the object in the form of heat.

When the shape of the asteroid is very irregular the heat is not radiated evenly and this creates a tiny, but continuous, torque on the body and changes its spin rate.

Lowry's team measured that the YORP effect was slowly accelerating the rate at which Itokawa spins. The change in rotation period is tiny—a mere 0.045 seconds per year.

But this was very different from what was expected and can only be explained if the two parts of the asteroid's peanut shape have different densities.

This is the first time that astronomers have found evidence for the highly varied internal structure of asteroids.

Up until now, the properties of asteroid interiors could only be inferred using rough overall density measurements.

This rare glimpse into the diverse innards of Itokawa has led to much speculation regarding its formation.

One possibility is that it formed from the two components of a double asteroid after they bumped together and merged.

Lowry added, "Finding that asteroids don't have homogeneous interiors has far-reaching implications, particularly for models of binary asteroid formation."

"It could also help with work on reducing the danger of asteroid collisions with Earth, or with plans for future trips to these rocky bodies."

This new ability to probe the interior of an asteroid is a significant step forward, and may help to unlock many secrets of these mysterious objects.

More information: This research was presented in a paper "The Internal Structure of Asteroid (25143) Itokawa as Revealed by Detection of YORP Spin-up", by Lowry et al., to appear in the journal Astronomy & Astrophysics.

First Asteroid of 2014 Spotted: 2014 AA

This animated GIF shows Asteroid 2014 AA, discovered by the NASA-sponsored Catalina Sky Survey on Jan. 1, 2014, as it moved across the sky. 

Credit: CSS/LPL/UA

Early Wednesday morning (Jan. 1, 2014), while New Year's 2014 celebrations were still underway in the United States, the Catalina Sky Survey near Tucson, Ariz., collected a single track of observations with an immediate follow-up on what was possibly a very small asteroid—7 to 10 feet (2 to 3 meters) in size—on a potential impact trajectory with Earth.

Designated 2014 AA, which would make it the first asteroid discovery of 2014, the track of observations on the object allowed only an uncertain orbit to be calculated.

However, if this was a very small asteroid on an Earth-impacting trajectory, it most likely entered Earth's atmosphere sometime between 11 a.m. PST (2 p.m. EST) Wednesday and 6 a.m. PST (9 a.m. EST) Thursday.

Steve Chesley

Using the only available observations, three independent projections of the possible orbit by the independent orbit analyst Bill Gray, of the Minor Planet Center in Cambridge, Mass., and Steve Chesley, of NASA's Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, Calif., are in agreement that 2014 AA would hit Earth's atmosphere.

According to Chesley, the potential impact locations are widely distributed because of the orbit uncertainty, falling along an arc extending from Central America to East Africa.

The most likely impact location of the object was just off the coast of West Africa at about 6 p.m. PST (9 p.m. EST) Jan. 1.

It is unlikely asteroid 2014 AA would have survived atmospheric entry intact, as it was comparable in size to asteroid 2008 TC3, which was about 7 to 10 feet (2 to 3 meters) in size.

2008 TC3 completely broke up over northern Sudan in October 2008. Asteroid 2008 TC3 is the only other example of an object discovered just prior to hitting Earth.

So far, there have been a few weak signals collected from infrasound stations in that region of the world that are being analyzed to see if they could be correlated to the atmospheric entry of 2014 AA.