WEST LAFAYETTE, Ind. \u2014 Rocks that stood out as light-colored dots on the reddish-orange surface of Mars now are the latest evidence that areas of the small planet may have once supported wet oases with humid climates and heavy rainfall comparable to tropical climates on Earth.<\/p>\n\n\n\n
The rocks discovered by NASA\u2019s Perseverance Mars rover are white, aluminum-rich kaolinite clay, which forms on Earth after rocks and sediment are leached of all other minerals by millions of years of a wet, rainy climate.<\/p>\n\n\n\n
These findings<\/a> were published Monday (Dec. 1) in the peer-reviewed scientific journal Communications Earth & Environment by lead author Adrian Broz, a Purdue University postdoctoral research associate in the lab of Briony Horgan<\/a>, a long-term planner on NASA\u2019s Mars Perseverance rover mission and professor of planetary science in the Department of Earth, Atmospheric, and Planetary Sciences<\/a> in Purdue\u2019s College of Science<\/a>.<\/p>\n\n\n\n \u201cElsewhere on Mars, rocks like these are probably some of the most important outcrops we\u2019ve seen from orbit because they are just so hard to form,\u201d Horgan said. \u201cYou need so much water that we think these could be evidence of an ancient warmer and wetter climate where there was rain falling for millions of years.\u201d<\/p>\n\n\n\n Broz said tropical climates like rainforests are the most common environments to find kaolinite clay on Earth.<\/p>\n\n\n\n \u201cSo when you see kaolinite on a place like Mars, where it\u2019s barren, cold and with certainly no liquid water at the surface, it tells us that there was once a lot more water than there is today,\u201d said Broz, a postdoctoral collaborator on the Perseverance rover.<\/p>\n\n\n\n The kaolinite fragments, which range from pebbles to boulders, are the latest small pieces to the larger debate regarding Mars\u2019 climate billions of years ago. Initial examinations by the Mars rover\u2019s SuperCam and Mastcam-Z instruments were used to compare the kaolinite to similar rocks found on Earth. The Martian fragments could offer significant insight into not only the planet\u2019s past environmental stages, but also how Mars came to its current barren state.<\/p>\n\n\n\n Horgan said kaolinite also carries its own mystery. There is no major outcropping nearby where the light-colored rocks could have originated despite being scattered throughout the mission path Perseverance has followed since landing at the Jezero crater in February 2021. The crater used to contain a lake about twice the size of Lake Tahoe.<\/p>\n\n\n\n \u201cThey\u2019re clearly recording an incredible water event, but where did they come from?\u201d Horgan said. \u201cMaybe they were washed into Jezero\u2019s lake by the river that formed the delta, or maybe they were thrown into Jezero by an impact and they\u2019re just scattered there. We\u2019re not totally sure.\u201d<\/p>\n\n\n\n Satellite imagery has spotted large outcroppings of kaolinite in other areas of Mars.<\/p>\n\n\n\n \u201cBut until we can actually get to these large outcroppings with the rover, these small rocks are our only on-the-ground evidence for how these rocks could have formed,\u201d Horgan said. \u201cAnd right now the evidence in these rocks really points toward these kinds of ancient warmer and wetter environments.\u201d<\/p>\n\n\n\n Broz compared the Martian kaolinite samples examined by Perseverance with rock samples found in locations near San Diego, California, and in South Africa. The rocks from the two planets were a close match.<\/p>\n\n\n\n Aside from a rain-heavy tropical climate, Broz said kaolinite on Earth also forms in a hydrothermal system when hot water is leaching the rock. But that process creates a different chemical signature in the rock than leaching at lower temperatures by rain over thousands to millions of years. He said datasets from three different sites were used to compare the hydrothermal leaching scenario to the Mars rocks.<\/p>\n\n\n\n Rocks on Mars like the kaolinite are a similar time capsule, potentially holding information from billions of years ago about the history of environmental conditions on the planet.<\/p>\n\n\n\n \u201cAll life uses water,\u201d Broz said. \u201cSo when we think about the possibility of these rocks on Mars representing a rainfall-driven environment, that is a really incredible, habitable place where life could have thrived if it were ever on Mars.\u201d<\/p>\n\n\n\n Purdue University is a public research university leading with excellence at scale. Ranked among top 10 public universities in the United States, Purdue discovers, disseminates and deploys knowledge with a quality and at a scale second to none. More than 106,000 students study at Purdue across multiple campuses, locations and modalities, including more than 57,000 at our main campus locations in West Lafayette and Indianapolis. Committed to affordability and accessibility, Purdue\u2019s main campus has frozen tuition 14 years in a row. See how Purdue never stops in the persistent pursuit of the next giant leap \u2014 including its integrated, comprehensive Indianapolis urban expansion; the Mitch Daniels School of Business; Purdue Computes; and the One Health initiative \u2014 at https:\/\/www.purdue.edu\/president\/strategic-initiatives<\/a>.<\/p>\n\n\n\n Alteration history of aluminum-rich rocks at Jezero crater, Mars<\/em>About Purdue University<\/h2>\n\n\n\n
Paper<\/h2>\n\n\n\n
Communications Earth & Environment
DOI: https:\/\/doi.org\/10.1038\/s43247-025-02856-3<\/a><\/p>\n\n\n