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  Model crater Linné & why we needed asteroidsNov 08, 2012 1:57 AM PST | url
 
Added 1 new A* page:NASA has created a video about the 1.4 mile-wide Linné Crater on the Moon; Linné is so remarkably young, for a lunar crater--just 10 million years old!--and untouched by other asteroid strikes that it is still in "pristine" condition, and thus perfect for studying a crater in its most basic form. One of the big surprises so far is that it isn't actually a bowl shape, but more of an inverted cone shape--implying that other craters we see get their bowl shapes due to erosion of the original cone shape.
 
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This article talks about a new study that has presented the theory that an asteroid belt like the one we have in our solar system between Mars and Jupiter is necessary to the formation of life; not only may these icy and rocky asteroids, hitting a planet, provide that planet with the water and organic molecules necessary to create life, but major asteroid strikes, like the one on Earth 65 million years ago that wiped out the dinosaurs, allowing mammals to evolve and proliferate, may be essential to evolution (granted, we may have a bit of a bias in that particular case). And even more specifically, this theory says that the asteroid belt has to be at about the distance that the Mars-Jupiter belt is from its central star, which is beyond the "snow line" where it is cold enough for water and vital gases to condense and collect into ices; furthermore, you need a massive, Jupiter-sized planet out there to keep disrupting the belt with its gravity, preventing it from collapsing and forming into its own planet, and probably also shaking things loose to go sail toward the inner planets. This all further suggests that, with these conditions being relatively narrow, life as we know it may be less common throughout the galaxy than some earlier estimates (*cough* Sagan *cough*) had expected.
 
 
 
 
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