NASA’s fashion new rover Perseverance Mars may be attracting all the attention these days, but its predecessor Curiosity is still making progress.
More than 2,000 miles away from the landing site of Perseverance, Curiosity has wandered the crater of Mars Gale for the past nine years. Since 2014, it has been slowly climbing a 3-kilometer-high mountain in the center of the crater: Mount Sharp. There, Curiosity discovered signs that ancient Mars was experiencing wild climate fluctuations – it oscillated between the water world being rich in rivers and the dry desert planet, according to a study published on Thursday.
Scientists have known for decades that Mars lost water about 3.5 billion years ago, but a new discovery suggests that the lakes and rivers on the planet may have disappeared and returned several times before they completely disappeared. Compiling a history of water on Mars can help scientists understand if it has ever hosted life.
Curiosity is likely to reveal more secrets about Mars ’past as it explores the foothills of Mount Sharp, where billions of years of Martian history are embedded in 3km of rock layers. Each era of the planet’s history has left different traces on the mountain – layers of sediment from the course of an ancient river, clay that once settled to the bottom of a lake or dust and sand blown by a dry valley. As the rover climbs, it embarks on a chronological tour of Mars’ climate history.
Recently, a rover reached the base of a mountain of sediments half a mile thick in the area.
“We are now arriving at a very interesting location,” William Rapin, a planetary scientist from the French National Center for Scientific Research and lead author of the new study, told Insider.
NASA has assigned Curiosity this extended mission, which has an indefinite time frame, after the rover completed its original mission in 2014. In the first two years on Mars, Curiosity confirmed that Gale Crater was once a lake filled with chemicals for life. (Perseverance is now exploring a similar bed of ancient Lake Martian in search of fossils of ancient microbial life.)
Since then, Curiosity has discovered organic material, sniffed out mysterious jumps in methane levels in Mars ’atmosphere, measured the red planet’s gravitational field, and uncovered evidence that tiny, salty ponds remained behind Mars. Curiosity still solves the puzzle of Martian history, little by little.
Curiosity’s laser camera detected unusual layers of stone
As curiosity crawled across Mount Sharp, her ChemCam instrument pierced the surrounding rocks with a laser. This evaporates pieces of rock, and the instrument can then analyze the light wavelengths of the resulting gases. From there, scientists can determine what chemicals are in the rock. The instrument also includes a telescope that can detect rock features five to ten times smaller than what previous rovers could record in high resolution.
“That’s why we targeted this place with this rover, so we could explore a mile-thick stratigraphy of ancient Martian history for the first time,” Rapin said. “For the first time, we could see how the sediment was laid.”
Using his telescope, Curiosity’s ChemCam discovered drastic changes in the rock bed as he climbed the mountain. The ancient lake left mineral deposits at the foot of Mount Sharp. Above that lake layer, Curiosity discovered horizontal streaks that were probably created by the wind blowing sand dunes across the crater. Above that there is another lake layer.
All of this together suggests that Gale Crater crossed from the lake into a dry, dry desert and then back into the lake. Rapin and his team believe that such drastic climate fluctuations could have occurred several times before Mars’ surface water completely dried up. It is not clear how long these wet and dry periods lasted, but Rapin thinks these are orders of millions of years.
“It’s really the first time we can start setting a climate history on a scale of millions of years,” he said.
Understanding how Mars has transformed from an aquatic world full of habitable environments into a barren planet could help scientists better assess the likelihood of the existence of extraterrestrial life and where to hunt it.
“I’m not surprised what we’re discovering and I really hope the rover stays well and continues to roam,” Rapin said. “We have a lot to learn.”