Has NASA found evidence of ancient life of Mars? An expert examines the latest discovery

NASA has announced the first detection of possible biosignatures in a rock on the floor of Mars. The rock comprises the primary martian natural matter to be detected by the Perseverance rover, in addition to curious discolored spots that might point out the previous exercise of microorganisms.

Ken Farley, mission scientist on the mission, has referred to as this “essentially the most puzzling, complicated, and probably essential rock but investigated by Perseverance.”

Perseverance is a part of Mars 2020, the primary mission since Viking that’s explicitly designed to hunt life on Mars (formally, to “seek for potential proof of previous life utilizing observations concerning habitability and preservation as a information”). Arguably, that goal has now been achieved: potential proof for previous life has been discovered. However far more work is required to check this interpretation of the information. This is what we do know.

Since touchdown in Jezero crater a couple of years in the past, Perseverance has traversed a sequence of rocks shaped practically 4 billion years earlier than current. Mars again then was way more liveable than the chilly, dry, poisonous pink planet of at present.

There have been 1000’s of rivers and lakes, a thick environment, and cozy temperatures and chemical circumstances for all times. Most of the rocks in Jezero are sedimentary: mud, silt and sand dumped by a river flowing right into a lake.

The brand new discovery issues one among these rocks. Informally named “Cheyava Falls” (a waterfall in Arizona), it’s a small reddish block of what seems like a mudstone, enriched with natural molecules. The rock can also be laced with parallel white veins. Between the veins are millimeter-scale whitish spots with darkish rims. For an astrobiologist, all these options are intriguing. Let’s take them one-by-one.

First, “organic molecules”, are made from carbon and hydrogen (generally with sulfur, oxygen or nitrogen as properly). Examples embrace the proteins, fat, sugars, and nucleic acids from which all life as we all know it’s constructed.

Natural matter is frequent in rocks on Earth, most of it derived from the stays of historical organisms. However the time period “natural” is barely deceptive: such molecules may also be produced by non-biological reactions (in truth, we know this was happening 4 billion years in the past on Mars).

Easy non-biological natural molecules are frequent within the universe, and NASA’s Curiosity rover already discovered them in mudstones in Gale Crater. They have been additionally reportedly detected by Perseverance in Jezero crater final yr.

Nonetheless, Ken Farley considers the brand new statement the primary actually “compelling detection” of organics made by Perseverance. NASA has not informed us which forms of organic molecules are literally current in Cheyava Falls, so it’s laborious to guage their origins. They may turn into organic, however a full evaluation utilizing laboratories on Earth can be wanted to settle this query.

Subsequent, the veins. These are composed of calcium sulfate, which precipitated like limescale when liquid water ran alongside fractures within the subsurface. Veins like these are frequent in Martian sedimentary rocks (Curiosity noticed loads of them), and naturally they aren’t “biosignatures” although they usually symbolize liveable circumstances.

My own work has shown that microorganisms inhabiting subsurface fractures can produce chemical fossils that get trapped in calcium sulfate veins. Surprisingly, nevertheless, the veins in Cheyava Falls additionally include olivine, an igneous mineral. This would possibly counsel that the water was injected at temperatures too excessive for all times. We want extra knowledge to know in some way.

Lastly, what about these whitish, discolored spots? These seem like the “discount spots,” additionally referred to as “leopard spots,” generally seen in pink sedimentary rocks on Earth. Such rocks are rusty-red as a result of they include an oxidized type of iron. When chemical reactions modify the iron to a much less oxidized state, it turns into soluble. Water carries the pigment away, leaving a bleached spot behind.

On Earth, these reactions are sometimes pushed by subsurface-dwelling micro organism. They use the oxidized iron as a supply of power, simply as you and I exploit oxygen within the air. On Mars, bacteria-like organisms might have used the organic matter within the rock to finish the response (simply as we use glucose from the meals we eat).

Discount spots have not been seen earlier than on Mars, though bleached linear “halos” noticed by Curiosity in Gale crater are considerably related. As one of many few astrobiologists to have studied discount spots on Earth—and located proof for organic processes inside them—I’m personally delighted. However as ever, warning is required.

Potential non-biological causes have to be explored and dominated out. Iron-dissolving reactions can and do occur in sedimentary rocks with out life. The darkish margins of the Cheyava Falls spots are enriched in each iron and phosphate, an affiliation beforehand instructed to happen round some calcium sulfate veins on Mars. This statement is in keeping with life, but in addition with chemical reactions pushed by acidic fluids.

The brand new findings will however embolden these calling on NASA and the European Area Company to proceed with the troubledmulti-billion-dollar sample retrieval program, which Perseverance was supposed to start. The rover has now cored out a chunk of the Cheyava Falls rock. If present plans are realized—a giant if—then future spacecraft will acquire this piece (and others) and convey it to Earth.

It is going to then be analyzed in state-of-the-art laboratories way more succesful than the devices aboard Perseverance. Till that occurs, we can’t be certain whether or not Perseverance has actually discovered fossils of historical life on Mars. The proof to date will not be definitive, however it’s definitely tantalizing.

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