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NASA's Dawn spacecraft has provided researchers with the firstorbital analysis of the giant asteroid Vesta, yielding new insightsinto its creation and kinship with terrestrial planets and Earth'smoon. Vesta now has been revealed as a special fossil of the early solarsystem with a more varied, diverse surface than originally thought.Scientists have confirmed a variety of ways in which Vesta moreclosely resembles a small planet or Earth's moon than anotherasteroid. Results appear in this week's edition of the journalScience. "Dawn's visit to Vesta has confirmed our broad theories of thisgiant asteroid's history, while helping to fill in details it wouldhave been impossible to know from afar," said Carol Raymond, deputyprincipal investigator at NASA's Jet Propulsion Laboratory inPasadena, Calif. "Dawn's residence at Vesta of nearly a year hasmade the asteroid's planet-like qualities obvious and shown us ourconnection to that bright orb in our night sky." Scientists now see Vesta as a layered, planetary building blockwith an iron core - the only one known to survive the earliest daysof the solar system. The asteroid's geologic complexity can beattributed to a process that separated the asteroid into a crust,mantle and iron core with a radius of approximately 68 miles (110kilometers) about 4.56 billion years ago. The terrestrial planetsand Earth's moon formed in a similar way. Dawn observed a pattern of minerals exposed by deep gashes createdby space rock impacts, which may support the idea the asteroid oncehad a subsurface magma ocean. A magma ocean occurs when a bodyundergoes almost complete melting, leading to layered buildingblocks that can form planets. Other bodies with magma oceans endedup becoming parts of Earth and other planets. Data also confirm a distinct group of meteorites found on Earthdid, as theorized, originate from Vesta. The signatures ofpyroxene, an iron- and magnesium-rich mineral, in those meteoritesmatch those of rocks on Vesta's surface. These objects account forabout 6 percent of all meteorites seen falling on Earth. This makes the asteroid one of the largest single sources forEarth's meteorites. The finding also marks the first time aspacecraft has been able to visit the source of samples after theywere 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 nearlyvertical sides, with landslides occurring more frequently thanexpected. Another unexpected finding was that the asteroid's central peak inthe Rheasilvia basin in the southern hemisphere is much higher andwider, relative to its crater size, than the central peaks ofcraters on bodies like our moon. Vesta also bears similarities toother low-gravity worlds like Saturn's small icy moons, and itssurface has light and dark markings that don't match thepredictable patterns on Earth's moon. "We know a lot about the moon and we're only coming up to speed nowon Vesta," said Vishnu Reddy, a framing camera team member at theMax Planck Institute for Solar System Research in Germany and theUniversity of North Dakota in Grand Forks. "Comparing the two givesus two storylines for how these fraternal twins evolved in theearly solar system." Dawn has revealed details of ongoing collisions that battered Vestathroughout its history. Dawn scientists now can date the two giantimpacts that pounded Vesta's southern hemisphere and created thebasin Veneneia approximately 2 billion years ago and the Rheasilviabasin about 1 billion years ago. Rheasilvia is the largest impactbasin on Vesta. "The large impact basins on the moon are all quite old," said DavidO'Brien, a Dawn participating scientist from the Planetary ScienceInstitute in Tucson, Ariz. "The fact that the largest impact onVesta is so young was surprising." Launched in 2007, Dawn began exploring Vesta in mid-2011. Thespacecraft will depart Vesta on August 26 for its next studytarget, the dwarf planet Ceres, in 2015. The e-commerce company in China offers quality products such as China Bearing Steels , Alloy Steel Round Bar, and more. For more , please visit Plastic Mold Steel today!
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