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.


 
 

 
Image courtesy of NASA Ames/JPL-Caltech/T Pyle

NASA’s Kepler reborn, makes first exoplanet find of new mission

Image courtesy of NASA Ames/JPL-Caltech/T Pyle The artistic concept shows NASA’s planet-hunting Kepler spacecraft operating in a new mission profile called K2. Using publicly available data, astronomers have confirmed K2&...
 
 
NASA illustration

NASA, planetary scientists find meteoritic evidence of Mars water reservoir

This illustration depicts Martian water reservoirs. Recent research provides evidence for the existence of a third reservoir that is intermediate in isotopic composition between the Red Planetís mantle and its current atmosphe...
 
 
Lockheed Martin photograph

Lockheed Martin-built MUOS-3 satellite encapsulated in launch vehicle fairing

Lockheed Martin photograph The U.S. Navy’s Mobile User Objective System-3 satellite (above) is encapsulated in its payload fairings for a scheduled Jan. 20, 2015 launch aboard a United Launch Alliance Atlas V rocket. MUOS ope...
 

 
NASA photograph

NASA’s Orion arrives back at Kennedy

NASA photograph NASA’s Orion spacecraft returned to the agency’s Kennedy Space Center in Florida Dec. 18, 2014. The spacecraft flew to an altitude of 3,600 miles in space during a Dec. 5 flight test designed to stre...
 
 

NASA launches new Micro-g NExT for undergraduates

NASA is offering undergraduate students an opportunity to participate in a new microgravity activity called Micro-g Neutral Buoyancy Experiment Design Teams. The deadline for proposals is Jan. 28, 2015. Micro-g NExT challenges students to work in teams to design and build prototypes of spacewalking tools to be used by astronauts for spacewalk training in the...
 
 
launch1

Storm fails to quench liftoff of secret reconnaissance satellite

The fiery launch of an Atlas V (541), among the most powerful of the venerable Atlas family, briefly dispelled the gloom over Californiaís Central Coast on the evening of Dec. 12. A team of personnel from United Launch Allianc...
 




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>