Ruby-Forming Mineral on Mars Hints at Violent Meteorite Impacts

NASA's Perseverance rover has found small, pale rocks in Mars' Jezero Crater that carry tiny grains of corundum, the same mineral that forms rubies and sapphires on Earth. The discovery, described in a new study in the journal Geophysical Research Letters by a team led by Ann Ollila of Los Alamos National Laboratory, hints that some Martian surface rocks were shaped by violent meteorite impacts rather than the volcanic and water-driven processes that explain most of the planet's known minerals.

Most of what scientists understand about Martian geology comes from rocks that formed from ancient volcanic lava and were later altered by long periods of water flowing through them. But as Perseverance travelled along the rim of Jezero Crater in 2025, it came across small rocks that looked out of place, apparently carried in from elsewhere rather than part of the surrounding bedrock. Using its SuperCam spectroscopic instrument, the rover detected corundum in these rocks — a finding the researchers called strange, since corundum normally needs abundant aluminum and very little silicon, yet the rocks were also rich in a silicon-heavy mineral that should have consumed the available aluminum first.

To explain the puzzle, Ollila's team looked at the violent origin of Jezero Crater itself, which was carved out by a massive meteorite impact capable of generating enough heat and pressure to alter the chemical make-up of rocks. The tiny grain size of the corundum, combined with the rocks' location right on the crater rim, led the researchers to conclude that the minerals were most likely formed suddenly during the impact, with fluid moving through the rocks afterward further altering their chemistry.

The rocks lie close to other, similar corundum-bearing rocks near the rim of Jezero Crater, the researchers noted, describing a formation pathway that differs from the volcanic and water-altered rocks documented elsewhere on Mars.