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One of the biggest surprises during the first months of the Dawn mission (the probe in orbit around the asteroid Vesta), has been the discovery of a huge mountain that rises almost 21 km above its surroundings
(photo above). A huge protrusion when we consider Everest is 2.5 times smaller, and that the largest mountain in the solar system, Olympus Mons on Mars, is 27 km high.
But the most interesting thing is not that this mountain is on a body that is only 530 km across itself, but rather that this region seems to be the origin of many of the meteorites that fall to Earth. Over the years, a spectroscopic similarity between many meteorites and Vesta has been noted, suggesting a common chemical composition and hinting at a common origin. The fall of some of these meteors has been witnessed (October 1999, Bilanga Yanga, Africa; October 1960, Millbillillie, Australia).
Now that the Dawn probe has identified a huge mountain, which is thought to have been created by an impact with another asteroid, the idea that this could have been the event which liberated a huge number of fragments, some of which have since fallen to Earth, seems to gain credence.
To investigate this possibility further, a group of researchers at UCLA led by Chris Russell (Dawn Principal Investigator) will attempt to date the Vesta impact event via the level of cratering on its surface near the mountain. This is possible thanks to the fact that the impact has deleted all trace of pre-existing craters in the region, so that those now present should hold information about how long ago the event occurred.
This estimate of the age of the event can then be compared with estimates of the age of the meteorites based on radioactive isotope ratios. If the ages are similar, then an explanation as to why so many 'Vesta' meteorites have fallen on Earth may have been found.
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by Michele Ferrara & Marcel
Clemens |
credit: NASA |
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