Earth and Mars formation processes differ, study finds

A study led by the University of Copenhagen suggests that Earth and Mars formed through significantly different processes, despite originating from the same rotating cloud of gas and dust 4.5 billion years ago.

Researchers analyzed chemical compositions in the crust and mantle of both planets to reconstruct their early development. The findings, published in Nature Astronomy, indicate that Earth’s mass is largely derived from two protoplanets that grew through pebble accretion—the accumulation of millimeter- to centimeter-sized particles. At least 75 per cent of Earth’s mass appears to have come from these larger planetary embryos.

In contrast, Mars appears to have formed primarily through collisions with planetesimals, which are kilometer-sized solid building blocks. Approximately 73 to 75 per cent of Mars's mass originated from these planetesimals, with only about a quarter coming from pebble accretion. This research supports a hybrid model of rocky planet formation where the relative importance of pebble accretion versus planetesimal collisions varies between worlds.