Scientists suspect that the surface of Mars was once filled with water, a lush oasis filled with river systems and lakes, until dramatic changes in Mars’ magnetic field caused it to lose much of its atmosphere, turning it into the arid hellscape we know today.
Now, an unusual new set of rocks discovered by NASA’s Perseverance Mars rover suggests the Red Planet’s ancient history was wetter and more tropical than scientists previously thought, an intriguing new question in our efforts to figure out whether the planet was ever habitable.
As detailed in a new paper published in the journal Communications Earth & EnvironmentA team of researchers analyzed the rocks, which have interesting light-colored dots ranging in size from pebbles to boulders. They suspect it’s the aluminum-rich kaolinite clay, which formed after millions of years of humid, rainy weather on Earth absorbed all the other minerals from it.
“Elsewhere on Mars, rocks like this may be among the most important outcrops we see from orbit because they are so difficult to form,” co-author Briony Hogan, a professor of planetary science at Purdue University and a member of NASA’s Perseverance team, said in a statement. “You need so much water, we think these could be evidence of an ancient warm, humid climate where there was millions of years of rainfall.”
On Earth, kaolinite clay is most commonly found in tropical climates such as rainforests, suggesting Mars may have once been home to lush oases. The team compared the rocks with samples from San Diego, California and South Africa and found interesting similarities.
“So when you see kaolinite in a place like Mars, which is barren, cold, and has no liquid water on the surface, it tells us that there was once a lot more water than there is now,” added lead author Adrian Broz, a postdoctoral researcher at Purdue University.
The rover found fragments of kaolinite in numerous places along its path to Jezero Crater, which is suspected to be a giant dry lake bed — a discovery that left scientists with a conundrum.
“They clearly documented incredible water events, but where did they come from?” Hogan said in the statement. “Maybe they were washed into Lake Jezero by the rivers that formed the delta, or maybe they were thrown into Lake Jezero by an impact and then scattered there. We’re not entirely sure.”
Larger outcrops of light-colored rock could help them solve the mystery, but that would require closer observation by Perseverance.
“But until we actually get to these large outcrops with rovers, these small rocks are our only ground-based evidence of how these rocks were formed,” Hogan said. “Now the evidence in these rocks really points to a warmer, wetter environment in ancient times.”
“All life needs water,” Broz added. “So when we think about the possibility that these rocks on Mars represent a rainfall-driven environment, it really makes sense that this would be an incredibly hospitable place where life could potentially thrive, if there was life on Mars.”
As well as painting a fascinating picture of ancient tropical oases on Mars, researchers believe the rocks may also shed new light on how the Red Planet turned into a barren wasteland – an extreme transformation that remains a mystery to this day.
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