Rosettawatch: Onion layers prove 67P is a slow-mo comet mash-up

[muriel_volestrangler]

It’s the slow-motion crash site that we can’t take our eyes off. The latest findings from the European Space Agency’s Rosetta spacecraft have confirmed earlier suspicions that comet 67P/Churyumov-Gerasimenko was formed by two small bodies coming together at less than walking speed.
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Matteo Massironi, a geologist at the University of Padova, Italy, and his colleagues have now studied the high-resolution images streaming back from the spacecraft and say the erosion scenario just won’t wash. They examined layers of material, or strata, to infer the internal structure of 67P, and say it’s certain that it used to be two separate space rocks.

Because layers that are visible on exposed areas of the surface probably continue underground, linking up patches of strata provides a way to map what’s going on below. Before joining the Rosetta team, Massironi applied the same technique to plans for the Brenner Base Tunnel, a railway line currently under construction through the Alps. “I just borrowed that methodology and transported it to the comet,” he says.
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To firm up the finding, the researchers also calculated the direction of gravity at each point on the comet, which they expected to be at right angles to the strata if the comet was initially a single body.

https://www.newscientist.com/article/dn28249-rosettawatch-onion-layers-prove-67p-is-a-slow-mo-comet-mash-up/