Mars had a Tropical Climate, According To Weird, Pale Jezero Rocks

Mars was a wet, warm, humid planet bathed in heavy rains around 4 billion years ago, when life on Earth likely arose. New evidence continually reveals more details about Mars’ downright tropical past, painting a picture of an incredibly hospitable world — in stark contrast to the planet we see today: barren, dusty, and rocky. This holds especially truer at the Jezero Crater.
Yet it’s some of these same rocky features that now offer additional clues about the many millions of years when the red planet was a lot bluer.
This newest Mars research comes courtesy of a recent study from Purdue University, in which scientists examined a number of oddly pale rock fragments found by the Perseverance rover during its travels through Jezero Crater, which once held a body of water about as large as Lake Tahoe. Intriguingly, these pale rocks are composed of a softish mineral called kaolinite, commonly found in Earth’s tropical areas, like rainforests:
“On Earth, these minerals form where there is intense rainfall and a warm climate or in hydrothermal systems such as hot springs. Both environments are ideal conditions for life as we know it,” explains Roger Wiens, co-author and the Purdue planetary scientist who led the design team for the Perseverance rover’s head-mounted SuperCam.
Accordingly, the researchers utilized SuperCam’s laser, camera, and spectrometers to examine the oddly light-colored rocks. They are hydrated and aluminum-rich, suggesting they formed due to extensive weathering, such as through rainfall sustained over millions of years, in conditions where warm, flowing water leeches away most of the elements within the rock, leaving only those that are truly insoluble.
Ranging in size from pebbles to boulders, these specimens are also known as “float rocks” because they’ve been carried away from where they formed and are not part of the bedrock. Where exactly they formed is still a mystery, though they may have been carried miles away from their origin by water and erosion, or scattered by impacts.
Outcroppings full of this kaolinite-rich material are globally abundant across the Martian equator and subequatorial regions, with dates spanning hundreds of millions of years across the Noachian period (4.1 to 3.7 billion years ago) and beyond.
And while Perseverance discovered pebble-sized float rocks the day it landed, scientists are only recently finding the time to precisely analyze the thousands of available fragments.
Their existence also implies that even though our red neighbor is barren and hostile to life as we know it, it’s “possible that a lot of the water is still there, on Mars, bound up in the minerals.”
These minerals can also help explain how Mars become so dry: since Mars lacks the tectonic forces that help recycle the water in these rocks back into the atmosphere, via volcanic eruptions, it’s possible that these rocks may have contributed to drying Mars by hoarding its atmospheric moisture.
Additional research is warranted. As the study concludes, these kaolinite-forming conditions examined are linked to the “wettest, and possibly most habitable portions of Mars’ history,” even perhaps reminiscent of past greenhouse climates on Earth.