Mars's dense layer reveals the fate of rocky planets ⚡ экспресс
In the early stages, terrestrial planets were covered by an ocean of magma, whose crystallization determined the structure of the mantle. Recent seismic data pointed to a silicate layer at the base of Mars' mantle, but no such layer exists on Earth. The authors modeled how partial melting in the growing mantle influenced the composition of the overlying magma ocean. It turns out that mantle melts act as a 'buffer,' limiting iron accumulation and layering. This effect is stronger on larger planets with active convection (mixing), which is why Earth's mantle is better mixed, while Mars retained a dense lower layer. The study predicts that distant exoplanets divide into two types: some maintain a layered mantle, others an almost homogeneous one.
If you don’t stir a layered cocktail, the heavy syrup sinks to the bottom. A young planet is much the same—a seething ocean of molten rock. As it cools, minerals crystallize: some, like iron, get heavy and sink, while others float. You’d think a dense layer would pile up at the core.
But from below, out of the solidifying depths, melts rise: light droplets, like oil in water, float up and churn the ocean. The bigger the planet and the hotter the 'stirring,' the harder it is for iron to settle.
The Martian ocean was shallower, the heat-driven motion weaker, and the iron quietly flowed to the bottom. This layer was recently detected through the echoes of marsquakes—it acts like a sponge, damping seismic waves.
The discovery explains the inner structure of many rocky exoplanets. In essence, we’ve read the recipe nature uses to cook up planetary interiors: some it stirs, others it lets separate into layers.
🎯 If Earth's interior had been as calm as Mars's, we would have formed a hidden dense layer too—and that would have completely changed the planet's look: continents would have moved differently, volcanoes would have erupted differently.