On our planet, corundum typically forms in the deep layers of the Earth's crust, where high temperature and pressure prevail.
The Perseverance rover has discovered spectral signs of the mineral corundum in rocks at the edge of Jezero Crater, from which rubies and sapphires are formed on Earth. Such spectra have been recorded for the first time on the Red Planet. Now scientists are trying to understand the processes that could have led to its formation there, as conditions on Mars differ significantly from those in which corundum typically forms on Earth.
NASA's Perseverance rover made a soft landing in Jezero Crater. This location was chosen by scientists for a reason: the crater was once filled with water, meaning that traces of ancient life could have been preserved there.
The rover is equipped with state-of-the-art technology. One of its main tools is the SuperCam. It is a true Swiss Army knife in the world of spectroscopy. It not only photographs rocks but also irradiates them with a laser to determine their chemical composition. When the laser hits the rock, it vaporizes a microscopic layer of material and creates plasma, the radiation of which the instrument analyzes by comparing it with the characteristic spectral 'signatures' of various minerals.
An international team of geologists and planetary scientists led by Ann Ollila from Los Alamos National Laboratory in New Mexico (USA) used SuperCam to study the light inclusions found in three rocks from Jezero Crater: Hampden_River, Coffee_Cove, and Smiths_Harbour.
Previous analysis showed that these structures are rich in plagioclase—a common mineral in basaltic and other magmatic rocks, which is often found on Mars. Scientists expected to see the typical luminescence of plagioclase, but instead, they received a clear signal of trivalent chromium (Cr³⁺).
Time-resolved luminescence spectroscopy showed peaks of Cr³⁺ characteristic of corundum, into which chromium is incorporated. On Earth, it is chromium that gives corundum its red color, turning it into ruby.
In simpler terms: the instrument recorded not the mineral itself but its spectral signature (imprint). Corundum is aluminum oxide Al₂O₃, which is colorless in its pure form, and the presence of chromium in its structure provides the signals that suggest a mineral similar to ruby in composition. At the same time, the authors of the study noted that no large grains of corundum were seen in the camera images; the particles were very small—less than 200 micrometers in diameter.
On our planet, corundum typically forms in the deep layers of the Earth's crust, where high temperature and pressure prevail. This most often occurs in metamorphic rocks rich in aluminum, as well as in some magmatic rocks. The movement of tectonic plates creates these extreme conditions, redistributes minerals, and allows aluminum to crystallize into aluminum oxide—corundum. Impurities of chromium or titanium give it red or blue colors, creating rubies and sapphires.
Mars lacks active tectonics, so researchers suggest that corundum could have formed under the influence of shock waves from meteorites, which generate extreme temperatures and pressures conducive to the recrystallization of aluminum into corundum.
The research results were presented at the Lunar and Planetary Science Conference 2026 in Texas (USA).
