The transition zone from a clay-rich region to one filled with a salty mineral called sulfate has been traveled through by the rover. The transition zone is proving to be more interesting than the clay-rich region and sulfate-laden one that were targeted by the science team. The record of a major change in Mars' climate billions of years ago may be provided by this transition.
The base of Mount Sharp is the location of the clay minerals formed when lakes and streams once existed. The streams dried into trickles and sand dunes formed above the lake when they were higher on the mountain.
"We no longer see the lake deposits that we saw for years lower on Mount Sharp," said Ashwin Vasavada, the project scientist at NASA. Dry dunes that occasionally had streams running around them are some of the evidence of drier climates. The lakes that persisted for millions of years before have changed.
The rover is detecting more sulfate as it climbs higher. A more detailed glimpse into the changing mineral composition of the rocks will be provided by the last rock sample that will be taken by the rover.
There are unique geological features in this zone. The hills in the area probably began in a dry environment of large, wind-swept sand dunes. Water can be found in the remains of the dunes and deposited in ponds or small streams. These are stacks of flaky layers that are erosion resistant.
The knowledge that there were multiple periods in which the water ebbed and flowed is making the story more complicated.
It has been ten years and going strong.
It will be 10 years on Mars on August 5. Even though the rover is showing its age after a decade of exploration, nothing has stopped it from continuing its climb.
On June 7, the rover went into safe mode after detecting a temperature that was warmer than expected. When a spacecraft senses an issue and shuts down all but its most essential functions, it's in safe mode.
JPL's engineers are still analyzing the cause of the issue two days after the issue was solved. They think safe mode was triggered after a temperature sensor provided an inaccurate measurement, but there's no sign it will affect rover operations since backup temperature sensors can ensure the electronics are not getting too hot.
There are signs of wear on the wheels. On June 4, the engineering team told the rover to take new pictures of its wheels to check their health.
The zig-zagging treads on the left middle wheel were damaged. Five of the wheel's 19 grousers are broken.
Some of the metal between the grousers appears to have fallen out of the wheel in the past few months and attracted attention online.
The team decided to return to the original cadence by increasing its wheelimaging to every 1,640 feet. Increasing the distance between images was justified by slowing wheel wear.
Megan Lin, the project manager at JPL, said that ground testing has shown that they can safely drive on the wheel rim. If a majority of the grousers were broken by a single wheel, we could take a break and remove the remaining pieces. It seems like we wouldn't need to do that due to recent trends. The traction we need is provided by the wheels.
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