Heat could be retained as debris fall back into impact craters, creating an insulating blanket.

当碎片落回撞击坑时，热量可以被保留下来，形成隔热层。

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The Mariner spacecraft found that the surface of Mars, as well as that of its two moons, is pitted with impact craters formed by meteoroids falling in from space.

水手号宇宙飞船发现火星表面，还有它的两个卫星表面，都有由太空坠落的流星体造成的陨石坑。

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From the small number of impact craters that appear on Martian lava flows, one can estimate that the planet was volcanically active as recently as a half-billion years ago—and may be active today.

从火星熔岩流上出现的少量陨石坑中，我们可以估计，在5亿年前，这个星球上的火山还很活跃——也许现在依然活跃。

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What's more, Pratt said his map showed that the feature is circular, which is characteristic of impact craters.

MSN: Massive meteorite crater found in Canadian Arctic

The Shoemakers also travelled each year to the well-preserved impact craters in Australia.

ECONOMIST: Gene Shoemaker

Shoemaker was studying asteroid impact craters in Australia and once said he would like to take a geologist's hammer to Eros.

BBC: At a glance: Asteroid touchdown