Dawn at Vesta

NASA’s Dawn probe has recently reached orbit around Vesta, and has started to return data. Since it’s astronomy-related, a lot of that data is in the form of pictures, for instance:

Credit: Dawn/NASA, via Wikipedia.

Doubtless many more will follow.

Vesta is an interesting object. It’s one of the biggest of the main-belt asteroids. It’s large enough to be somewhat-spherical, having an average diametre of 529 km. (There’s a lot of variation, though – it’s a ball, but a lumpy ball!) It’s beig enough that its surface gravity is actually about two percent that of the Earth. You’d be heavy enough there that you certainly wouldn’t float away, but a jump from a cold start would carry you many feet straight up.

A quick bit of (somewhat-unscientific) experimentation suggests that I can jump about 20 cm straight up, from a cold start. On Vesta, the same amount of downward-force would translate into just over nine metres straight up. Or put it another way, if the building I live in was on Vesta, I could jump from the garden outside to the top of the roof. (It’s probably just as well the building I live in isn’t on Vesta … goodness only knows what some of the neighbours would do if they could jump onto the roof!)

There is some evidence to suggest that, structurally, Vesta is more akin to a planet than you would expect an asteroid to be. We tend to picture asteroids as largely-undifferentiated rocky masses. However, various meteors have reached the Earth from Vesta, and these meteors seem to suggest a different picture. Rather, they seem to suggest that Vesta has a core/mantle/crust structure, rather like a planet.

It may even have experienced internal convection and surface vulcanism during its early years, before the mantle would have frozen solid. Strange to picture volcanoes on an asteroid! An interesting question that doubtless the Dawn people are looking into, I suppose, will be whether or not any of these putative volcanoes have survived into the present day. Although they obviously won’t still be active now, their cones/shields might still be visible on the asteroid’s surface.

So, Vesta is a fascinating object and like many others, I await developments with much curiosity!


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