Clay minerals were formed when lakes and streams flowed across the Gale Crater, depositing sediments in the area now the source of Mount Sharp, a 3-mile (5-kilometer) mountain range under Curiosity that has been rising since 2014. on a mountain in the transition area, Curiosity’s observations indicate that streams dried up into dunes formed above the lake floor.
“We are no longer seeing the lake deposits we have seen for years on Mount Sharp,” said Ashwin Vasavada, a Curiosity project scientist at NASA’s Jet Propulsion Laboratory in Southern California. “Instead, we see a lot of evidence of dry weather.”
As the rover climbs higher into the transition area, it sees less clay and more sulfate. Curiosity will soon be digging for the last rock sample to be taken from the site, providing a more detailed view of the mineral composition of these rocks.
Different geologic features also stand out in this zone. The hills in this area probably originate in the arid region of giant, windswept sand dunes, which harden into rocks over time. Among the remnants of these mounds are other water-carrying debris, perhaps deposited in lakes or small streams that once flowed between the mounds. These remnants now appear as erosion-resistant stacks of loose layers, such as the so-called “Prow.”
To make the story more prosperous and more difficult is the knowledge that there have been many times when groundwater recedes and flows over time, leaving many puzzling pieces for Curiosity scientists to come together into an accurate timeline.