So you might imagine that the crust forms a solid, complete shell, like an eggshell around a softer inside.

所以你可以想象成地壳形成了一个坚实的完整的外壳，就像蛋壳包裹着更软的内部一样。

It tells from a time when mars were just 100 million years old, this was a turbulent period and scientists believed the piece have crust formed as volcanoes erupted all over the planet's surface.

当时火星的年龄只有一亿年，那是个充满动荡不定的时期，科学家认为这块石头表面的壳表明当时火星表面到处都有火山爆发。