NASA’s Perseverance rover discovered corundum—the crystalline mineral behind rubies and sapphires—within three pale, plagioclase-rich rocks along the rim of Jezero Crater.
Laser Spectroscopy Reveals Martian Corundum
When NASA’s Perseverance rover directed its onboard laser at pale float rocks scattered across the Jezero Crater rim in 2025, the instrument’s time-resolved luminescence (TRL) spectroscopy produced an entirely novel spectral signal. The rocks, identified as Hampden River, Coffee Cove, and Smiths Harbour, yielded the unmistakable signature of chromium-bearing corundum.
Corundum forms as aluminum oxide in crystalline structures. On Earth, trace amounts of the element chromium substitute for aluminum atoms inside the crystal lattice to produce the distinctive pinkish-red hues of rubies.
According to research published in Geophysical Research Letters, finding corundum in a Martian setting surprised scientists because the mineral requires bulk chemical compositions enriched in aluminum and depleted in silicon. Ordinarily, abundant silicon binds with available aluminum to create silicate rocks like plagioclase feldspar. Because all three corundum-bearing float rocks discovered by the rover were themselves dominated by plagioclase, their coexistence presents a geological puzzle.
Ancient Impact Dynamics and Hydrothermal Activity
Because the three discoveries are float rocks—loose boulders sitting on the surface rather than attached bedrock—their exact original formation site remains uncertain. Researchers analyzing the data suggest the minerals may have formed when hot water moved through cracks in the rock millions or even billions of years ago. Such hydrothermal conditions support crystal growth and provide further evidence that water once played an important role in shaping the Martian landscape.
Beyond fluid interactions, scientists examining the regional geology point to another major mechanism: the colossal impact that excavated Jezero Crater itself. Modeling studies led by planetary scientists exploring ancient Martian impacts indicate that planet-scale collisions can dredge up deep-seated materials and fling them across the surface. Alexander Trowbridge of the SETI Institute and his colleagues used numerical simulations to reconstruct the massive 3.9-billion-year-old impact that carved out the neighboring Isidis basin—a scar stretching more than 930 miles across.
Simulations tracking debris dispersal show that impact shock waves capable of squeezing minerals to extreme pressures between 6.5 and 8.7 million pounds per square inch can loft rocks from deep within the Martian mantle. While previous missions recovered numerous samples of surface lavas and lake sediments, identifying rocks bearing the scars of extreme shock pressure offers a reliable field marker for material originating far beneath the crust.
Curiosity Encounters a Vast Sea of Polygons
While Perseverance investigates the crater rim, NASA’s Curiosity rover has documented a completely different style of geological puzzle while climbing through a valley nicknamed “Valle Grande.” Panoramic images captured during sols 4,930 and 4,931 revealed the valley floor covered in honeycomb-like polygonal fractures measuring 1.5 to 3 inches across.
The geometric patterns climb the flanks of a nearby 20-foot-tall butte named “Miraflores,” which is capped by a thick layer of sand. Although Curiosity has encountered small groups of polygons during its 14-year journey across the Red Planet, the sheer scale of the Valle Grande polygon field surprised the mission team.
Researchers evaluating the honeycomb structures are weighing multiple formation hypotheses. While some polygonal formations observed previously began as mud cracks indicating ancient wet-dry cycles, other physical mechanisms can generate identical geometry. Repeated warming and cooling can fracture the ground into geometric shapes, and sediment burial can force trapped water outward through compression.
Piecing Together the Red Planet’s Deep History
Both rover missions continue to add detail to an increasingly complex picture of ancient Mars. The polygonal terrain documented by Curiosity builds upon earlier discoveries by William Rapin and colleagues at France’s Institut de Recherche en Astrophysique et Planétologie regarding seasonal wetting and drying cycles that could support molecular evolution. Concurrently, Curiosity’s ascent up Mount Sharp has uncovered carbon-based organic molecules believed to be precursors to RNA and DNA alongside sulfur crystals and reflective meteorites.
The detection of corundum along the Jezero rim and the modeling of deep mantle ejecta reinforce the view that Mars experienced extensive thermal and dynamic activity. Perseverance continues sealing rock cores inside titanium tubes, building a cache intended for a future return flight to Earth, where laboratories could examine mantle chemistry and gemstone signatures atom by atom.
