Image Credit: Ollila et al., Geophys. Res. Lett., 2026

NASA’s Perseverance rover has detected what appears to be chromium-bearing corundum in three rocks at Mars’ Jezero Crater, marking the first reported identification of the mineral on the Red Planet. On Earth, corundum is the crystalline material that forms rubies and sapphires.

The discovery came after Perseverance examined three pale, plagioclase-rich rocks using its SuperCam instrument in 2025. The laser-based analysis revealed distinctive signatures of chromium-bearing corundum, a finding that researchers say is difficult to explain given the chemistry of the Martian rocks. The findings were reported in Geophysical Research Letters.

The rocks, named Hampden River, Coffee Cove and Smiths Harbour, are all “float rocks,” meaning they are no longer attached to the bedrock where they originally formed. Perseverance analyzed them in March, April and July 2025 using time-resolved luminescence spectroscopy, which uses a laser to excite minerals and measures the light they emit.

All three samples produced two prominent luminescence peaks at 692.7 and 694.1 nanometers. Those signals are characteristic of corundum containing chromium, the same element responsible for the red or pink color of rubies. In the Smiths Harbour sample, the glow also lasted roughly 3 milliseconds, matching measurements from corundum found on Earth.

The discovery is surprising because corundum generally forms in environments rich in aluminum and relatively poor in silicon. The three Martian rocks, however, are dominated by plagioclase, an aluminum-silicate mineral that normally incorporates much of the available aluminum.

Researchers believe several processes could potentially explain the unusual combination. Volcanic activity or interactions with hot fluids are possibilities, but the team considers a massive impact that created Jezero Crater billions of years ago a particularly interesting explanation.

The impact would have subjected surrounding rocks to extreme heat and pressure. Evidence of ancient hydrothermal activity in the crater could also have allowed fluids to alter the rocks’ chemistry, creating conditions favorable for corundum formation.

The evidence remains indirect, however. Finding the original outcrop from which the float rocks came would provide stronger clues about their history. Researchers say returning a core sample to Earth would allow far more detailed testing and could help determine exactly how the corundum formed.

For now, Perseverance has not found fields of Martian rubies, but it has uncovered a mineralogical puzzle that could reveal more about the ancient geological history of Mars.