“We are well into the layers that were the main reason Gale Crater was chosen as the landing site,” says Curiosity Deputy Project Scientist Joy Crisp. Four years after touching down on the red planet, Curiosity continues its trek up the slopes of Mount Sharp. And its latest discovery adds another notch into the possible past habitability column.
As NASA’s rover climbs the layered Mount Sharp, it’s finding evidence of how ancient lakes and wet underground environments changed billions of years ago. The just announced discovery of boron points to complexity in the old lake environments.
“There is so much variability in the composition at different elevations, we’ve hit a jackpot,” said John Grotzinger. He’s part of Curiosity’s science team, a team “impressed” by the new discoveries made by their little rover.
“A sedimentary basin such as this is a chemical reactor,” Grotzinger adds. “Elements get rearranged. New minerals form and old ones dissolve. Electrons get redistributed. On Earth, these reactions support life.”
Illustration showing the environment around Curiosity today and how scientists believed it looked billions of years ago. Credit: NASA
We still don’t have an answer for if Martian life ever existed. Scientists have yet to find the ‘smoking gun’ for life on the red planet. But they are finding conditions that potentially tease an environment conducive for microbes to grab hold.
When Curiosity first touched down in Gale Crater, scientists examined the surrounding area to see if such an environment ever existed. They found the ancient Martian lake environment had the right chemical ingredients and the energy. The trip up Mount Sharp will try to fill in the how the conditions in the area changed billions of years ago.
“We are now using a strategy of drilling samples at regular intervals as the rover climbs Mount Sharp,” says Crisp. “Earlier we chose drilling targets based on each site’s special characteristics. Now that we’re driving continuously through the thick basal layer of the mountain, a series of drill holes will build a complete picture.”
From June through October, Curiosity drilled at four sites spaced nearly 80 feet apart. The new drill samples show hematite replacing magnetite (less-oxidized) as the main iron oxide in rock samples.
NASA’s Thomas Bristow explains what this means. “Both samples are mudstone deposited at the bottom of a lake, but the hematite may suggest warmer conditions, or more interaction between the atmosphere and the sediments.”
Boron is another element Curiosity is seeing. And it’s the first mission to detect it on Mars. Boron is an exciting discovery because it is often associated with dry environments where the water has evaporated away.
Bottom line, the recent discoveries made by Curiosity point to a dynamic system says Grotzinger. “They [minerals] interact with groundwater as well as surface water. The water influences the chemistry of the clays, but the composition of the water also changes. We are seeing chemical complexity indicating a long, interactive history with the water. The more complicated the chemistry is, the better it is for habitability. The boron, hematite and clay minerals underline the mobility of elements and electrons, and that is good for life.”
On Earth, the Curiosity team is using a test rover to set up diagnostic tests to figure out the problem. They want to run the tests on Earth first before sending the command to Curiosity millions of miles away.
“To be cautious, until we run the tests on Curiosity, we want to restrict any dynamic changes that could affect the diagnosis. That means not moving the arm and not driving, which could shake it,” says Curiosity Deputy Project Manager Steven Lee.
A couple of possibilities the team is looking into center on the brake on the drill feed mechanism not disengaging all the way, or a problem with an electronic encoder for the motor.
So far, Curiosity used its drill on 15 rock targets. At each one, the drill combined hammering action and rotary action to collect samples. On Dec. 1, the team was trying to drill using only rotary action for the first time. “We still have percussion available, but we would like to be cautious and use it for targets where we really need it, and otherwise use rotary-only where that can give us a sample,” says Curiosity Project Scientist Ashwin Vasavada.
As of yesterday (Dec. 13), Curiosity is still undergoing diagnostics. As the rover waits to get rolling again, it’s snapping pictures of its surroundings.