Mars’ enduring role in the search for life

On the stage that is the search for life beyond Earth, Mars has spent a long time in the spotlight. The planet next door shows evidence of a more Earthlike past, with liquid water abundant on the surface. Many missions have visited Mars over the decades to study its potential for life, whether long ago in its watery past or somehow persisting today. In recent years, other worlds have started to creep closer to center stage: Europa and Enceladus with their huge subsurface oceans of liquid water and even Titan with its alien seas of liquid hydrocarbons. Mars was never displaced as a promising world in the search for life, but it increasingly shared the limelight with these other worlds. This year, though, two discoveries proved that Mars would not be upstaged anytime soon.

The first big announcement came in July from NASA’s Perseverance mission, along with a selfie. The Mars rover had found a rock, partially buried in a dry riverbed, with a smattering of black and white spots across its surface. On Earth, such “leopard spots” are mainly known to form in two ways: from microbes or through chemical reactions that can provide fuel for life. This is far from conclusive evidence of past life on Mars, but it’s the most intriguing hint of life we’ve found so far. And even if these spots weren’t created by living processes, they at least suggest that the building blocks of life may be common on Mars. Only by bringing the rock back to Earth for further study can we know what caused those leopard spots. But no matter what, the picture of Mars as a habitable planet is getting clearer.

The red planet wasn’t finished surprising us yet. In August, a team of scientists analyzing data from NASA’s now-defunct InSight lander shared evidence of huge amounts of liquid water beneath Mars’ surface. InSight’s mission was to study Marsquakes, and the data it collected can tell us things about the rock those tremors travel through. Through these insights, researchers can tell that the planet’s midcrust, about 10-20 kilometers (6-12 miles) down, may be riddled with cracks and pores filled with water — enough to cover all of Mars with an ocean over a kilometer deep. If Mars does have liquid water hidden beneath its surface, it could be hiding life there as well. Yet again, we can’t know for certain what’s down there until we explore further. 

With these tantalizing discoveries hinting at Mars’ potential for life, one thing is clear: This planet will always have a role to play in humanity’s search for our cosmic kin.