NASA’s flashy new Perseverance Mars rover may be getting all the attention these days, but its predecessor, Curiosity, is still making breakthroughs.
More than 2,000 kilometers from Perseverance’s landing site, Curiosity has been orbiting Mars’ storm surge crater for the past nine years. Since 2014, it has been slowly climbing the 3-kilometer mountain in the center of the crater: Mount Sharp. Curiosity has discovered signs that ancient Mars experienced wild climatic fluctuations – ranging from a water world rich in rivers to a dry desert planet, according to a study published Thursday.
Scientists have known for decades that Mars lost its water about 3.5 billion years ago, but the new discovery suggests that the lakes and rivers of the planet may have disappeared and returned several times before disappearing completely. Compiling the history of water on Mars can help scientists find out if it ever offered life.
Curiosity is likely to discover more secrets about Mars’ past as it explores the foothills of Mount Sharp, where billions of years of Mars history are embedded in 3 miles of rock. Each era of the planet’s history left different marks on the mountain – low sediment from the flow of an old river, clay that once lay on the bottom of the lake, or dust and sand blown over a dry valley . As the rover climbs, it gets a chronological tour of Mars’ climatic history.
Recently, the rover reached the base of a half-mile thick mountain of sediment in the area.
“We are now arriving at a very interesting place,” William Rapin, a planetary scientist at the French National Center for Scientific Research and lead author of the new study, told Insider.
NASA awarded Curiosity this extended mission, which has an indefinite timeline, after the rover completed its original mission in 2014. In the first two years on Mars, Curiosity confirmed that the Gale Crater was once a more lifelong fill with the chemical ingredients. (Perseverance is now investigating a similar ancient Martian bed in search of fossils from ancient microbial life.)
Since then, Curiosity has discovered organic matter, sniffed the mysterious spikes in the methane levels of the Martian atmosphere, measured the red planet’s gravitational fields, and found evidence that small, salty ponds remained behind as Mars dried up. Curiosity is still building the puzzle of Mars history little by little.
Curiosity’s laser camera detects curious low rock
An illustration of the Jezero crater, as it looked billions of years ago on Mars, when it was a lake.
NASA / JPL-Caltech
While Curiosity climbed Mount Sharp, the ChemCam instrument plunged the surrounding rock beds with lasers. It evaporates pieces of rock, and the instrument can then analyze the light wavelengths of the gases being analyzed. From there, scientists can determine which chemicals are present in the rock. The instrument also contains a telescope that can see rocks, is five to ten times smaller than previous high-resolution rovers could capture.
“That’s why we headed to this site with this rover to explore for the first time a mile-thick stratigraphy of ancient Mars history,” Rapin said. “We could see for the first time how the sediment was laid.”
Using its telescope, Curiosity’s ChemCam discovered drastic changes in the rock bed as it climbed the mountain. An ancient lake left mineral deposits at the foot of Mount Sharp. Above the multilayer, Curiosity discovers horizontal stripes probably made by wind dunes blowing across the crater. Above there is another multilayer.
The sedimentary structures observed in ChemCam’s telescope images.
NASA / JPL-Caltech / MSSS / CNES / CNRS / LANL / IRAP / IAS / LPGN
Collectively, this indicates that the storm surge went from a lake to a dry, arid desert, and then again to a lake. Rapin and his team think that such drastic climatic fluctuations may have occurred several times before Mars’ surface water completely dried up. It is not clear how long these periods of wet and dry lasted, but Rapin thinks it is in the order of millions of years.
“This is really the first time we can start writing a climate history down to millions of years,” he said.
Understanding how Mars transformed from a water world full of habitable environments to an arid planet can help scientists determine the probability that a strange life exists, and where to hunt for it.
“I’m not surprised we’re making discoveries, and I really hope the robber stays well and keeps moving around,” Rapin said. “We have a lot to learn.”