More than 15 months after landing in Jezero Crater on Mars, NASA’s Perseverance rover has finally begun its hunt for ancient life in earnest.
On 28 May, Perseverance ground a 5-centimetre-wide circular patch into a rock at the base of what was once a river delta in the crater. This delta formed billions years ago when a long-gone river deposited layers in Jezero. It is the main purpose that NASA sent the rover there .. River sediment on Earth is often teeming in life.
Images taken from the freshly ground spot show small sediment grains. Scientists hope these will contain chemical or other signs of life. Sanjeev Gopta, a planetary geologist at Imperial College London, on twitter ., wrote that William Blake’s poem “To see a whole world in a grain or sand” comes to mind.
The rover will spend the next few month exploring the Jezero Delta, while mission scientists decide on where to drill and extract rocks samples. NASA and the European Space Agency (ESA) plan to retrieve those samples and fly them back to Earth for study, no earlier than 2033, in the first-ever sample return from Mars.
‘Going for the buffet ‘
Perseverance landed in February 2021, several kilometres from the delta’s edge. It spent many of its early months exploring the crater floor — which unexpectedly is made of igneous rocks, a type that forms as molten materials cool. This was a scientific breakthrough because scientists can date igneous rock based on radioactive decay of their chemical components. Many researchers wanted Perseverance to reach the delta, where fine-grained sediments have a better chance of containing evidence of Martian life.
The rover finally reached the base of the delta in April. It soon found grey, thinly layered rocks known as mudstones. These could have been sediments that were deposited by slow rivers or lakes. It also discovered sandstones with coarse grains that could have formed in a fast flowing river. These kinds of rock are excellent targets for studying a variety of Martian environments where life could have thrived, Katie Stack Morgan, Perseverance’s deputy project scientist at the Jet Propulsion Laboratory (JPL) in Pasadena, California, said on 17 May during the online portion of the 2022 Astrobiology Science Conference.
Mission engineers drove Perseverance out of this area, called Enchanted Lake and towards Hawksbill Gap where it is currently operating. The newly abraded patch was made from a sandstone in one the lowest rock layers of the delta. This means that it is one the oldest rocks formed in Jezero’s ancient stream and makes it an excellent spot to hunt for signs ancient life.
The delta rises about 40 metres above the crater floor. Perseverance will be sent by Rover drivers to the delta’s front and back again to assess where and how to collect samples. Jennifer Trosper, JPL’s project manager for the mission, says that it’s like eating at a buffet before you eat. It will survey the rocks and even remove more to view the interiors of the rocks on the way up. It will drill for samples and collect the most interesting ones on the way down.
Mission scientists are deciding which rocks to sample in order to create the most diverse and geologically rich cache. It’s like a child making a collection of precious gemstones. Perseverance carries 43 tubes for samples, each a little thicker than a pencil. NASA and ESA are planning to bring around 30 filled tubes back to Earth.
Mission scientists have already begun to plan where to place the first set of samples that a future spacecraft will retrieve. The rover will likely place some tubes at the base of the delta, which is located in an area between Enchanted Lake, Hawksbill Gap, and large, flat areas. “There is a strong possibility that we may put down a first cache” once the rover reaches there, says Kenneth Farley (mission’s project scientist, and geochemist at California Institute of Technology in Pasadena). “That’s when it becomes .”
Mission planners didn’t expect to lay down samples this quickly, but the site is great — flat and without any rocks that could hinder a future sample return spacecraft. Trosper states, “It’s just great place to land in Mars.”
NASA will organize a September community meeting for planet scientists to evaluate whether the collection has been’scientifically worthy enough’ to be taken up. This is a crucial question due to the amount of time and money needed to return the tubes. Farley states that NASA wants the wider community to assess the view of the mission team that “we have assembled most valuable cache that we believe this site offers to us”.
A productive mission
NASA, ESA are working together on a US$5 billion plan to send two landers (with a rover to pick up the samples and a rocket to send them into Mars orbit) to Mars. The spacecraft would also grab them from orbit and fly them back home to Earth. The first launches were supposed to happen in 2026, but that timeline was changed by Russia’s invasion of Ukraine. Russia’s invasion of Ukraine caused the ESA to stop all cooperation with Russia’s satellite agency. The tensions have derailed a planned Russian-European Mars rover — and now NASA and ESA are redrawing their Mars-landing plans. They have time: Perseverance’s sampling tube is designed to withstand Martian conditions for many decades.
Perseverance made other discoveries in Jezero. These included how dust devils loft large quantities of dust in the air and how sound speed fluctuates in Mars’s carbon dioxide-rich atmosphere. The rover has so far driven more than 11 kilometres, and it set an extraterrestrial distance record when it covered 5 kilometres in 30 Martian days, in March and April.
Perseverance’s sidekick The tiny helicopter Ingenuity , was instrumental in some of the rover’s achievements. But its time on Mars may be drawing to a close. Originally designed to make just 5 flights, it defied expectations by completing 28. It has helped to find the best routes for Perseverance from its high vantage point. It also surveyed the area at the delta’s base, where future missions might land.
In May, however Ingenuity lost communication due to dust blocking sunlight. The helicopter requires sunlight to charge its solar panels. Ingenuity may have difficulty flying in the future due to the Martian winter’s dusty skies and cold temperatures.
“No matter what happens,” Farley says, “Ingenuity has b