For the past 10 years, the Curiosity rover has travelled across the Martian terrain, looking for clues to the planet’s potentially habitable past. Recently, the car-sized robot drove through a transition zone, going from an area that may have once hosted lakes on the surface to one that signifies drier conditions for the Red Planet.
NASA’s Curiosity rover took note of the change in scenery higher up on a Martian mountaintop, which the robot has been climbing since 2014. The 5 km-tall Mount Sharp is the central peak in Mars’ Gale Crater, which the rover is exploring for signs of ancient water. At the base of Mount Sharp, Curiosity collected evidence for clay minerals that formed from lakes and streams that once ran through Gale Crater. But higher up on the mountain, those streams had seemingly dried up into trickles and sand dunes, which had formed above the lake sediments.
This so-called transition zone is marked by a shift from a clay-rich region to one filled with the salty mineral sulfate, and could potentially signify a major shift in Mars’ climate that took place billions of years ago. The higher up Curiosity goes on Mount Sharp, it detects less clay, and more sulfate. Curiosity will soon start drilling the last rock sample collected in the transition zone in hopes of learning more about the change in the mineral composition of the rocks in that area.
“We no longer see the lake deposits that we saw for years lower on Mount Sharp,” Ashwin Vasavada, Curiosity’s project scientist at NASA’s Jet Propulsion Laboratory, said in a NASA news release. “Instead, we see lots of evidence of drier climates, like dry dunes that occasionally had streams running around them. That’s a big change from the lakes that persisted for perhaps millions of years before.”
The area that Curiosity is currently exploring also boasts hills that may have formed in dry conditions, and those hills are marked by large, wind-swept sand dunes that likely hardened into rock over time, according to NASA. Meanwhile, the rover also found evidence of sediments that were carried over by streams of water through the sand dunes. Those sediments now appear as stacked layers of flaky-looking rocks.
Although Mars is a desolate, dry planet today, scientists believe that it may have once been habitable, hosting lakes and other bodies of water on its surface. Early on in its history, Mars somehow lost some of its atmosphere, and its water dried up. Various robotic missions, from NASA and other space agencies, have worked to piece together this ancient history. A newer Mars rover, Perseverance, landed on the planet in February 2021 and has been searching for microfossils — preserved evidence of ancient microbial life.
As it inches closer to its 10-year anniversary on Mars, Curiosity has started to show some signs of ageing. On June 7, Curiosity went into the dreaded safe mode when a temperature reading showed warmer temperatures than usual, according to NASA. The rover was back in action two days later, but NASA engineers are still looking into the cause of the issue, hoping that it won’t affect the rover’s operations as it climbs to the top of a new era of Martian history.