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<\/p>\nLIFE, especially the microbes too small to see, has left an indelible mark on rocks on Earth, creating minerals that would otherwise not be there.<\/p>\n
If some of those minerals turn up in rocks on Mars, is that not good evidence that life once existed there, too?<\/p>\n
Maybe.<\/p>\n
Nasa\u2019s Perseverance robotic rover has discovered such minerals in one particular rock on Mars. It came across the specimen in an outcrop of hardened mud along what was once a flowing river.<\/p>\n
\u201cI think it\u2019s very intriguing,\u201d Joel Hurowitz, a professor of geosciences at Stony Brook University on Long Island and a member of the Perseverance science team, said in an interview.<\/p>\n
He said he had worked on Mars missions for more than two decades and this was the most confident he had been of potential biosignatures in a Martian rock.<\/p>\n
\u201cThese observations, to me, are really compelling,\u201d he said.<\/p>\n
Hurowitz and his colleagues described their findings in a paper published in the journal Nature.<\/p>\n
During a news conference, Sean Duffy, the acting administrator of Nasa who is also the secretary of transportation, said: \u201cThis very well could be the clearest sign of life that we\u2019ve ever found on Mars.\u201d<\/p>\n
Nicola Fox, Nasa\u2019s associate administrator for the science directorate, added context that this was not a definitive conclusion.<\/p>\n
\u201cThis certainly is not the final answer,\u201d she said.<\/p>\n
The news conference highlighted a divide in the stated priorities for Nasa during the Trump administration.<\/p>\n
Duffy in his remarks quickly pivoted from the agency\u2019s robotic science missions \u2013 a part of Nasa where the White House is looking to make deep budget cuts \u2013 to the agency\u2019s human spaceflight programme, including sending astronauts to the moon and eventually Mars.<\/p>\n
But he said that science was still important.<\/p>\n
\u201cScience isn\u2019t going away at Nasa,\u201d he said. \u201cWe are leaning into the science because we need it to make sure that we\u2019re successful on our missions to the moon and to Mars.\u201d<\/p>\n
A year ago, Nasa scientists were already giddy about this rock, because it possessed features that were reminiscent of what microbes could have left behind when this area was warm and wet several billion years ago, part of an ancient river delta.<\/p>\n
Jezero Crater, the landing site for Perseverance, was once a lake, and the sediments along the river that flowed into the crater were a promising place to look for signs of past life on Mars.<\/p>\n
However, Perseverance found few indications of it until this part of the riverbed, one of the rover\u2019s last stops before it exited the crater.<\/p>\n
The Nature paper describes in much greater detail the mineralogy of the rock, which the scientists named Cheyava Falls, and of the nearby terrain.<\/p>\n
\u201cLast summer was kind of a, \u2018Hey, we think we found something really interesting and cool\u2019,\u201d Hurowitz said.<\/p>\n
\u201cNow we\u2019re at the point where we\u2019re actually saying in detail, \u2018Here is what we have found\u2019.\u201d<\/p>\n
What attracted the most attention were what the scientists called poppy seeds \u2013 dark specks a few thousandths of an inch wide within the mudstone.<\/p>\n
The specks contain vivianite, an iron phosphate mineral.<\/p>\n
The scientists also observed larger features nicknamed leopard spots \u2013 dark rings containing vivianite surrounding off-white centres that included greigite, an iron sulfide mineral.<\/p>\n
\u201cThe leopard spots kind of look like they maybe started out as poppy seeds but were able to continue growing to a larger size,\u201d Hurowitz said.<\/p>\n
On Earth, vivianite and greigite often form in sedimentary deposits in freshwater lakes, river estuaries and marshlands.<\/p>\n
\u201cThese would be examples of microbially influenced environments where the microbes are consuming the organic matter and making these minerals as a byproduct,\u201d Hurowitz said.<\/p>\n
<\/p>\n
The minerals can also be produced by chemical reactions not involving living organisms.<\/p>\n
But in laboratory experiments, the greigite reactions require heating to more than 250\u00b0F, and, so far, it appears that the minerals on Mars formed at cooler temperatures.<\/p>\n
\u201cWithin the sort of limitations of our rover payload capabilities, they don\u2019t look like they\u2019ve been cooked,\u201d Hurowitz said.<\/p>\n
The rock also contains organic compounds \u2013 molecules with carbon and hydrogen \u2013 which adds more intrigue.<\/p>\n
Organic compounds are the building blocks for life, but those, too, can be produced by geological processes that have nothing to do with life.<\/p>\n
However, the rocks and the answers they hold may remain stranded on Mars indefinitely.<\/p>\n
Last year, the Mars Sample Return mission, which is to bring back the samples that Perseverance collected, was put on hold as cost estimates spiralled upward to US$11bil. Nasa then solicited proposals for alternative possibilities.<\/p>\n
In its budget request this year, the Trump administration sought to cancel the Mars Sample Return mission entirely.<\/p>\n
\u201cWe believe there\u2019s a better way to do this, a faster way to get these samples back,\u201d Duffy said during the news conference.<\/p>\n
\u201cAnd so that is the analysis we\u2019ve gone through. Can we do it faster? Can we do it cheaper? And we think we can.\u201d<\/p>\n
He did not provide any details about how or when.<\/p>\n
With Nasa\u2019s plans uncertain, the first rocks brought back from Mars could instead arrive on the other side of the planet. China is planning a robotic mission launching in 2028 to collect Martian rocks and drop them off on Earth three years later. \u2014 \u00a92025 The New York Times Company<\/p>\n