NASA’s Perseverance rover has discovered that a 28-mile-wide basin on Mars known as Jezero Crater preserves a complex water history where liquid soaked volcanic rocks at least three separate times in three different ways. Researchers examining data from 185 rocks across an 870-foot elevation range found that the crater’s margin unit—long thought from orbit to be an ancient shoreline—actually originated from cooled underground magma rather than lake sediment.
Volcanic Origins and Underground Magma Cooling
Scientists initially hoped to find sedimentary deposits along the crater’s edge to support orbital lake predictions. Instead, the rover’s SuperCam instrument revealed that the margin unit consists of igneous rocks. According to research led by Purdue University scientist Candice Bedford, published in Communications Earth & Environment, these formations began deep underground when cooling magma formed olivine, a mineral common in volcanic environments. Later erosion exposed these rocks at the surface, where carbon dioxide-rich groundwater seeped into cracks to create threads of carbonate minerals that outlasted the surrounding stone.
Did you know? Jezero Crater sits inside one of the largest exposures of carbonate on Mars, a mineral known for locking in traces of past microbes in environments similar to shallow Earth oceans.
Multiple Water Episodes and Carbonate Alteration
Further analysis revealed subsequent phases of aqueous activity that left distinct chemical signatures across the landscape. Eleni Ravanis, a co-author and planetary scientist at the University of Hawaii at Manoa, noted that turning olivine into carbonate leaves behind silica, which researchers detected in abundance below the former water line. In a separate study published in Science, led by Blue Marble Space Institute of Science research investigator Kenneth Williford, scientists examined similar carbonated ultramafic igneous rocks. Nikole Haney, a research geochemist and grant specialist with Texas State University’s Office of Research and Sponsored Programs’ Johnson Space Center Astromaterials Research Exploration and Science division who contributed to the Science study as a collaborating scientist on the SHERLOC instrument suite, stated that the findings provide in situ evidence of water-rock interaction on ancient Mars.
Pro tip: Instruments like SHERLOC use deep ultraviolet Raman spectrometry to study minerals and support ground-truthing of rover data collected directly on the Martian surface.
Hydrothermal Activity and the Search for Ancient Life
Perseverance also detected mineral veins containing calcium sulfate and fluorite in specific parts of the strip of land. These minerals point to a third wet episode involving hot water passing through the volcanic rocks, resembling a terrestrial hot spring system. While the rover data found no direct evidence of life, a site that experienced repeated wet episodes provides microbial life with multiple opportunities to emerge and leave behind biosignatures. The rover has collected samples from the formation, though future analysis depends on whether NASA can overcome funding setbacks for the Mars Sample Return mission, which faced congressional cancellation in January.
Frequently Asked Questions
What is the margin unit in Jezero Crater?
The margin unit is an elevation range of about 870 feet explored by Perseverance along the rim of Jezero Crater. Although it resembled an ancient shoreline from orbit, rover instruments revealed it consists of altered igneous volcanic rocks rather than lake sediments.
Why are carbonates important in the search for Martian life?
Carbonates are minerals that excel at locking in traces of past microbes. On Earth, these minerals frequently form in shallow oceans and lakes that support living organisms.
How many times did water interact with the margin unit rocks?
Data gathered by Perseverance indicates that water soaked the rocks at least three separate times in three different ways: through carbon dioxide-rich groundwater, lake-related aqueous activity, and a hot spring-like hydrothermal system.
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