Asteroid Science

Where would Asteroid Mappers be without the science? No where, that’s where!

You’d be doing useless tasks for no reason whatsoever. We wouldn’t ask you to do
that, so this page attempts to go through some of the major science questions we’re
trying to answer with Asteroid Mappers.

Figuring Out Vesta’s Surface History

Why do we care about craters? Craters can tell us a lot about what’s happening on a planetary surface. One of the main uses of craters is to tell ages. On the moon, we have a chronology that tells us that a surface that has a certain number of craters of a certain size will be a specific age. The basic idea is that if a surface has been around longer (it’s older), it will have accumulated more craters. See more about cratering ages on the Moon Mappers Science page.

The age of Vesta’s surface is really important to know, because it was probably one of the very first objects to fully form in the solar system. Vesta finished forming before the bigger planets (we know that because it is differentiated and because we can analyze samples of Vesta in the form of meteorites) so it’s probably recorded more history than any of these bodies.

But as it turns out, it’s not only the age of a planetary surface but also where you are in the solar system that can affect how many craters you accumulate. For a very long time, we only had the Earth and the Moon to look at to get information about what the early solar system looked like, but that was for our own cosmic neighborhood. The asteroid belt was a very different place, with more objects of varying sizes, so Vesta may have a totally different cratering history from other planets.

Vesta’s Geology

Vesta South Pole ScarpWe all expected to find craters on Vesta, and in particular the giant south polar impact basin now called Rheasilvia that was initially detected by Hubble Space Telescope data. But it turns out Vesta had a few things up her sleeve (see image right).

Vesta has a really thick “regolith”—the upper layer of its crust—probably from being pulverized in the asteroid belt for 4.5 billion years. All of that regolith is basically layer upon layer of impact ejecta, and there are places where these layers can be seen, and where their existence changes how the surface behaves. It’s been surprising to find so many features that show evidence for “mass wasting,” essentially land slides and other evidence for materials moving across the surface probably due to shaking by impacts and gravity (see image below).

Weird craters on Vesta

Ridges on VestaFew people expected to see tectonics—all those ridges and fractures criss-crossing and encircling Vesta. Vesta doesn’t have plate tectonics like Earth, Vesta’s tectonic features are almost certainly associated with the giant impact events. While Vesta is much like the planets in many ways, for example that it differentiated to form a core, mantle and crust, but its tectonic history is one of those places where Vesta acts like an asteroid (see image left).

Vesta has pit chains on its surface that look very similar to crater chains, but these are actually places where the thick regolith layer has been laid down over tectonic features, and then fallen in! (See image below.)

Boulder on Vesta

How and when all these features formed on Vesta is difficult to understand without a lot of context… that’s where mapping comes in! In a geologic map, scientists essentially trace out the different features, so that its easier to tell which one lay on top of or below other features. Then, we can determine the stratigraphy, essentially the layered history of the surface, and reconstruct Vesta’s past. In the coming months, new tools will be added and new projects to teach you how to become a geologic mapper (well, a simplified version of the real deal, since actually, it’s an art form) and to give scientists an idea of where to go with future citizen science. We are looking forward to figuring out just how good you are!

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