Mars' Hidden Rainy Past: Clues from Unusual Rocks

Mars, the dry and dusty planet we know today, might have once been a much wetter place. Recent findings from NASA's Perseverance rover suggest that tropical storms could have soaked the Red Planet for millions of years. The rover found light-colored rocks scattered around its path. These rocks, made of a clay called kaolinite, are a strong hint that Mars had a wet and humid past, much like Earth's tropical regions. On Earth, kaolinite forms over a long time as rainwater slowly removes other minerals from rocks. Finding this clay on Mars, where there's no liquid water today, suggests that the planet once had much more water than it does now. The kaolinite rocks found by Perseverance are quite large, some as big as boulders. They are similar to rocks found near San Diego, California, and in South Africa. However, the origin of these rocks is a mystery. There are no major rock formations nearby where they could have come from. Perseverance landed near Mars' Jezero crater, which once held a lake about twice the size of Lake Tahoe. The rocks might have been washed into the lake by a river or thrown in by an impact. Scientists are still trying to figure out the exact source. Satellite images have shown large kaolinite outcroppings elsewhere on Mars. But until the rover can reach these places, the small rocks found by Perseverance are the only direct evidence of how these rocks formed. The current evidence points to a past Mars that was warmer and wetter. Scientists are interested in Mars' water history because water is closely linked to life. On Earth, all life forms need water. So, if Mars once had a rainy environment, it could have been a habitable place where life might have thrived.