NASA's Curiosity rover made a compelling find on Mars' irradiated surface.
The car-sized robot's molecule-sleuthing instrument, called Sample Analysis at Mars, or SAM, identified the longest-ever-found organic compounds on Mars. They could be fragments of "fatty acids," a building block of earthly life that can compose cell membranes. While the discovery in Martian mudstone isn't nearly definitive proof of past life on Mars — these fatty acids can also be formed via non-biological processes — it does show that such potential evidence can be preserved in Mars' extremely harsh surface environs.
It also underscores that NASA's nuclear-powered rovers have done their job — identifying potential evidence of life — and that the samples must now be deeply scrutinized by scientists on Earth.
“We are ready to take the next big step and bring Mars samples home to our labs to settle the debate about life on Mars,” Daniel Glavin, the senior scientist for sample return at NASA’s Goddard Space Flight Center, said in a statement.
The debate about Martian life, however, won't be settled anytime soon. NASA's Mars Sample Return mission is in limbo as the space agency seeks out cheaper and simpler ways to transport samples (collected by Curiosity's sibling robot, Perseverance) in sealed, cigar-sized titanium tubes. Plans won't be finalized until 2026, and it's unlikely the samples will be returned to Earth before the mid-2030s.
These newly identified chains of organic molecules, which are based on carbon similar to much of life on Earth, certainly add more weight to the scientific merit behind the ambitious sample return endeavor. Such a journey to Mars and back may still cost some $6 to $8 billion. Specifically, the rock samples assessed by the Curiosity rover contain decane, undecane, and dodecane, which are composed of long chains of carbon atoms.
The research was published in the peer-reviewed journal Proceedings of the National Academy of Sciences.
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Adding to the samples' intrigue is where they were found. Curiosity drilled the rock from a region in the expansive Gale Crater called "Yellowknife Bay," which is an ancient, dried-up lakebed. On Earth, we know that life thrives in such watery, often nutrient-rich environs. Could it have done so on Mars, too?
"There is evidence that liquid water existed in Gale Crater for millions of years and probably much longer, which means there was enough time for life-forming chemistry to happen in these crater-lake environments on Mars,” Glavin, who coauthored the new Mars research, said.
What's more, each of the fatty acids detected in the rover's microwave-sized Sample Analysis at Mars instrument is a chain of carbons between 11 to 13 long. "Notably, non-biological processes typically make shorter fatty acids, with less than 12 carbons," NASA noted.
This all adds up to a significant amount of scientific intrigue — but no clear answers. Today, Mars is 1,000 times drier than the driest desert on Earth. But amid a warmer, hospitable climate — which hosted expansive lakes, long shorelines, and great Martian oceans — life might have found a way billions of years ago.
Hardy Martian life could have also once thrived well beyond the reach of NASA's rovers, deep in the Red Planet's subsurface, protected from radiation and climate extremes. But that's another story waiting to be written by another, future robot.
