More than fifteen months after landing in Jezero Crater on Mars, NASA’s Perseverance rover has finally begun its hunt for ancient life in earnest.
Two aspects of this mission stand out as momentous: First, the amazing technological achievements involved in sending remote-controlled craft to Mars, and second, the potential significance of finding signs of prior life on a planet other than Earth. What are the ramifications of a life signatures in Martian soil? Astronomers have already suggested that remnants of Earth-life has been “contaminating” Mars for millions of years. Sufficiently powerful meteorite collisions with Earth could eject Earth’s surface material (containing organisms) into an orbit that could eventually settle onto the surface of Mars.
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 of years ago, when a long-vanished river deposited layers of sediment into Jezero, and it is the main reason that NASA sent the rover here. On Earth, river sediment is usually teeming with life.
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. That was a scientific jackpot because scientists can date igneous rocks on the basis of the radioactive decay of their chemical elements. But many researchers have been keen for Perseverance to get to the delta, whose fine-grained sediments have the best chance of harbouring evidence of Martian life.
Like a child assembling a set of gemstones for their prized collection, mission scientists are deliberating over which rocks the rover should sample to amass the most geologically diverse cache. 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.
A productive mission
NASA and ESA are working on a US$5-billion plan to send two landers to Mars — carrying a rover that would pick up the samples, and a rocket that would send them into Mars orbit — as well as a spacecraft that would grab them out of orbit and fly them back to Earth. The first launches were supposed to happen in 2026, but that timeline was changed by Russia’s invasion of Ukraine. ESA halted all cooperation with Russia’s space agency over the war. The tensions have derailed a planned Russian–European Mars rover — and now NASA and ESA are redrawing their Mars-landing plans. They have some time: Perseverance’s sampling tubes are designed to last for decades under Martian conditions.
Along with taking rock samples, Perseverance has made other discoveries in Jezero, including how dust devils loft large amounts of dust into the air1 and how the speed of sound fluctuates in Mars’s carbon dioxide-rich atmosphere2. 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, has been instrumental in some of the rover’s achievements — but its time on Mars might be coming to a close. Originally designed to make just 5 flights, it defied expectations by completing 28. From its vantage point in the skies, it has helped to scout the best routes for Perseverance, and it surveyed the flat area at the delta’s base where future missions could land.
Nature