Fresh analysis of Mercury's surface composition has turned up a surprise: the planet's crust contains considerably less silicon dioxide than scientists previously believed. Because silica-rich rocks typically form during cooler, shallower melting, the low abundance points instead to lava that originated from deeper and more thoroughly melted parts of the mantle.
That interpretation gives Mercury an unexpectedly fiery past. The chemistry of the surface suggests ancient volcanic activity was driven by hotter, more extensive melting than standard models of the planet's interior had allowed for. The new results effectively rewrite the expected recipe for Mercury's crust, offering a clearer window into how the innermost planet evolved.