Space

May 10, 2012

NASA Dawn spacecraft reveals secrets of large asteroid

NASA’s Dawn spacecraft has provided researchers with the first orbital analysis of the giant asteroid Vesta, yielding new insights into its creation and relation to the terrestrial planets and Earth’s moon.

Vesta now has been revealed as a special fossil of the early solar system with a more varied, diverse surface than originally thought. Scientists have confirmed a variety of ways Vesta more closely resembles a small planet or Earth’s moon than another asteroid. Results appear in today’s edition of the journal Science.

“Dawn’s visit to Vesta has confirmed our broad theories of this giant asteroid’s history, while helping to fill in details it would have been impossible to know from afar,” said Carol Raymond, deputy principal investigator at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “Dawn’s residence at Vesta of nearly a year has made the asteroid’s planet-like qualities obvious and shown us our connection to that bright orb in our night sky.”

Scientists now see Vesta as a layered, planetary building block with an iron core – the only one known to survive the earliest days of the solar system. The asteroid’s geologic complexity can be attributed to a process that separated the asteroid into a crust, mantle and iron core with a radius of approximately 68 miles about 4.56 billion years ago. The terrestrial planets and Earth’s moon formed in a similar way.

Dawn observed a pattern of minerals exposed by deep gashes created by space rock impacts, which may support the idea the asteroid once had a subsurface magma ocean. A magma ocean occurs when a body undergoes almost complete melting, leading to layered building blocks that can form planets. Other bodies with magma oceans ended up becoming parts of Earth and other planets.

Data also confirm a distinct group of meteorites found on Earth did, as theorized, originate from Vesta. The signatures of pyroxene, an iron- and magnesium-rich mineral, in those meteorites match those of rocks on Vesta’s surface. These objects account for about 6 percent of all meteorites seen falling on Earth.

This makes the asteroid one of the largest single sources for Earth’s meteorites. The finding also marks the first time a spacecraft has been able to visit the source of samples after they were identified on Earth.

Scientists now know Vesta’s topography is quite steep and varied. Some craters on Vesta formed on very steep slopes and have nearly vertical sides, with landslides occurring more frequently than expected.

Another unexpected finding was that the asteroid’s central peak in the Rheasilvia basin in the southern hemisphere is much higher and wider, relative to its crater size, than the central peaks of craters on bodies like our moon. Vesta also bears similarities to other low-gravity worlds like Saturn’s small icy moons, and its surface has light and dark markings that don’t match the predictable patterns on Earth’s moon.

“We know a lot about the moon and we’re only coming up to speed now on Vesta,” said Vishnu Reddy, a framing camera team member at the Max Planck Institute for Solar System Research in Germany and the University of North Dakota in Grand Forks. “Comparing the two gives us two storylines for how these fraternal twins evolved in the early solar system.”

Dawn has revealed details of ongoing collisions that battered Vesta throughout its history. Dawn scientists now can date the two giant impacts that pounded Vesta’s southern hemisphere and created the basin Veneneia approximately 2 billion years ago and the Rheasilvia basin about 1 billion years ago. Rheasilvia is the largest impact basin on Vesta.

“The large impact basins on the moon are all quite old,” said David O’Brien, a Dawn participating scientist from the Planetary Science Institute in Tucson, Ariz. “The fact that the largest impact on Vesta is so young was surprising.”

Launched in 2007, Dawn began exploring Vesta in mid-2011. The spacecraft will depart Vesta on August 26 for its next study target, the dwarf planet Ceres, in 2015.

Dawn’s mission to Vesta and Ceres is managed by JPL for NASA’s Science Mission Directorate in Washington. Dawn is a project of the directorate’s Discovery Program managed by NASA’s Marshall Space Flight Center in Huntsville, Ala. UCLA is responsible for overall Dawn mission science. Orbital Sciences Corp. in Dulles, Va., designed and built the spacecraft. The German Aerospace Center, the Max Planck Institute for Solar System Research, the Italian Space Agency and the Italian National Astrophysical Institute are international partners on the mission team.

 




All of this week's top headlines to your email every Friday.


 
 

 

Headlines December 19, 2014

News: SpaceX’s attempt to land rocket on floating barge postponed - It’s set to be one of the most groundbreaking moments in humanity’s six decades of space exploration. Obama signs $1.1 trillion spending bill into law - President Obama signed the $1.1 trillion federal spending measure into law Dec. 16, officially ending any threat of a government...
 
 

News Briefs December 19, 2014

Trial set for ex-Navy engineer in military secrets case A former Navy civilian engineer is scheduled to stand trial next summer on charges of trying to steal aircraft carrier schematics. Media outlets report that 35-year-old Mostafa Awwad of Yorktown, Va., pleaded not guilty Dec. 17 to two counts of attempted exportation of defense articles and...
 
 
Army photograph by C. Todd Lopez

Army to launch cruise missile-detecting aerostat at Aberdeen Proving Ground

Army photograph by C. Todd Lopez The Army plans to launch an aerostat, part of the “Joint Land Attack Cruise Missile Defense Elevated Netted Sensor,” in late December 2014. The JLENS aerostat will be tethered to the...
 

 
Air Force photograph by SrA. Jordan Castelan

AF delivers Iraqi F-16s for training in US

Air Force photograph by SrA. Jordan Castelan Iraqi air force captain Hama conducts preflight inspections while inside a new to service Iraqi F-16 Fighting Falcon Dec. 17, 2014, located at the nearby Tucson International Airport...
 
 
Air Force photograph by SSgt. Derek VanHorn

Short-notice: A new way to exercise

Air Force photograph by SSgt. Derek VanHorn Airmen from Kadena Air Base, Japan, prepare for an aeromedical evacuation exercise on a KC-135 Stratotanker Dec. 5, 2014, at Misawa Air Base, Japan. The operation was executed in supp...
 
 
Lockheed Martin photograph by Andy Wolfe

Japan, Australia to provide F-35 maintenance sites in Pacific region

Lockheed Martin photograph by Andy Wolfe An F-35C Lightning II joint strike fighter carrier variant prepares to launch from the aircraft carrier USS Nimitz in the Pacific Ocean, Nov. 6, 2014. Japan and Australia will be sharing...
 




0 Comments


Be the first to comment!


Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>