深空视界
深空视界
Mars hasn't given us proof of life, but it has handed scientists a new kind of mystery.
On the western edge of Jezero Crater, NASA's has been exploring Neretva Vallis, a river-carved valley that once fed a vast Martian lake. There, in an outcrop of ancient mudstone called the Bright Angel formation, the rover found one of its : an arrowhead-shaped rock nicknamed Cheyava Falls, flecked with tiny black "poppy seeds" and ringed "leopard spots.""
signs of vivianite (an iron phosphate) and greigite (an iron sulfide). On Earth, both minerals typically form through redox reactions — the electron-swapping processes that underpin all life. Plants rely on redox in photosynthesis, humans and other animals use it to extract energy from food during respiration, and microbes employ it to "breathe" metals in oxygen-starved settings such as .On our planet, such signatures are often the fingerprints of biology. On , they remain a tantalizing "maybe" — chemical traces that could point to life, or could also arise from purely non-living processes. Either way, they mark a departure from the chemistry that scientists are used to seeing on the Red Planet.
"Whatever their origin, this is a very distinct chemistry than anything we've seen in ~20-25 years of roving the planet," Joel Hurowitz, a geoscientist at Stony Brook University in New York who led the recent study, told .
Even if the reactions turn out to be non-biological, he added, they could reveal "prebiotically useful chemistry we haven't thought about before," while also serving as a reminder of the ways that abiotic nature can mimic life's signals — false positives for "that we'll have to do some really hard thinking about.""
A window into Mars' past
Mars' surface usually tells a story of oxidation: iron reacting with oxygen billions of years ago, when liquid water and a thicker atmosphere were still present, leaving behind the global blanket of rust that earned Mars its enduring nickname, the Red Planet. At Cheyava Falls, however, Perseverance identified minerals that formed through the other half of the equation, known as reduction, where iron and sulfur gained electrons instead of losing them.