NASA's Curiosity Rover has come a long way since it came to Mars seven years ago. It has traveled a total of 13 miles (21 kilometers) and has climbed 207 feet (368 meters) to its present location. Along the way, Curiosity discovered that Mars had the conditions to sustain the life of germs in the ancient past, among other things.
And the rover is far from over, having just punched its 22nd sample from the surface of the Martian. It is still several years before its nuclear system is decommissioned enough to significantly limit its operation. Then a careful budgeting of its power will allow the rover to continue exploring the Red Planet.
Curiosity is already halfway through the region, which scientists call the "clay unit" on the side of Mount Sharp, inside Galle Crater. Billions of years ago there were streams and lakes in the crater. The water changes the sediment deposited in the lakes, leaving behind many clay minerals in the region. This clay signal was first discovered by NASA's Mars Reconnaissance Orbiter (MRO) space a few years before Curiosity launched.
"This area is one of the reasons we come to Galle Crater," said Kristen Bennett of the US Geological Survey, one of the flagships for the Curiosity Clay Campaign. "We have been studying orbital images in this area for 10 years, and we are finally able to get a closer look."
The rock samples that the rover drilled here revealed the highest amount of clay minerals found during the mission. Curiosity, however, has found similarly large amounts of clay in other parts of Mount Sharp, including in areas where MRO has not found clay. This made scientists wonder what caused the differences from orbit and surface.
The scientific team is considering possible reasons why the clay minerals here stand out before the MRO. The rover came across a "parking lot full of gravel and pebbles" when it first entered the area, said another campaign co-host, Valerie Foxx of Kaltech. One idea is that pebbles are key: Although the individual pebbles are too small to be seen by MROs, they can collectively appear in orbit as a single clay signal scattered around the area. Dust also settles more easily over flat rocks than over pebbles; the same dust can obscure the signals seen from space. The pebbles were too small to raise curiosity, so the scientific team was looking for other clues to solve this puzzle.
Curiosity left the pebble parking lot back in June and began to encounter more sophisticated geological features. He stopped to take a 360-degree panorama at sunrise called "Teal Ridge." Most recently, she took detailed images of Stratton, a rock made of dozens of sediments that solidified into a fragile wavy pile. Unlike the thin flat layers associated with the lake sediments Curiosity has studied, the wavy layers in these characteristics suggest a more dynamic environment. Wind, running water or both could shape this area.
Both Til Ridge and Stratton represent changes in the landscape. "We see an evolution in the ancient lake environment recorded in these rocks," Fox said. "It wasn't just a static lake. It helps us move from a simplified view of Mars that goes from wet to dry. Instead of a linear process, the history of the water was more complicated."
Curiosity reveals a richer, more complex story behind the waters of Mount Sharp – a process that Fox resembled in order to finally read the paragraphs in a book – a dense book with torn pages but a fascinating tale to blend together.
The NASA Curiosity Mars rover finds a clay cache
For more information on the NASA Curiosity Mars Rover Mission, visit mars.nasa.gov/msl/
New Findings for Mars Rover Seven Years After Landing (2019, August 6)
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