There is no evidence of microfossils on Mars, says a NASA planetary scientist
Since time immemorial, Mars has puzzled earthlings with the possibility that it might harbor life. But like a bad TV series, its exploration created astrobiological cliffhangers that mostly turned into dead ends.
Today, planetary scientists are confident that for a brief period of 500 million years early in its history, Mars had liquid water walking on its surface, with rivers, lakes, deltas, and perhaps even an ocean. However, the reality at present is that the surface of Mars is much more inhospitable than the drier deserts on Earth.
The surface is completely inhospitable, Jennifer Stern, a planetary scientist at NASA’s Goddard Space Flight Center in Maryland, told me. Besides the fact that there is no liquid water on the surface, Mars also suffers from a constant stream of cosmic and solar radiation, she says. It’s really hard to imagine that some kind of organism could adapt to these really bad conditions, Stern says.
From what we’ve measured at least on the surface, everything points to abiotic, non-biological processes, Stern says in a presentation last week at the 241st meeting of the American Astronomical Society (AAS) here in Seattle. She says the best hope for future Mars exploration lies in the Earth’s interior.
Stern notes in her AAS summary that a near-surface, undiscovered surface can maintain a habitable environment for longer than a surface. She writes that records of organic molecules may persist beyond the reach of ionizing radiation from galactic cosmic rays.
How has the Mars habitability paradigm changed since the Viking lander?
When NASA sent out two Viking landers, they really threw everything into the matter of life, says Stern.
But when they didn’t detect life, it was kind of the death knell for NASA’s Mars exploration over the next 25 years, she says.
Then as we went back in time, we started to think about what the most basic thing life needed to do, Stern asks. It is indisputable, she says, that water must exist for life as we know it to exist.
But so far, there is no definitive evidence of life on Mars.
With NASA’s Mars rover, and discoveries of complex organics in both the 3.8-billion-year-old Gale Crater and Jezero Crater mudstones, we now know that organic carbon is likely to be widely distributed on Mars, Stern noted in her AAS presentation. .
Certain organic molecules, such as amino acids and lipids, are more indicative of life and the things we see in the fossil record on Earth, Stern says. But we don’t see those particles on Mars, she says. We don’t see evidence of microfossils, says Stern.
Are we halfway to understanding Mars’ history of life?
I think we’re a long way off, says Stern. With the Curiosity and Perseverance rovers, we’ve confirmed the presence of carbon-bearing organic molecules on Mars, she says.
Is there currently any flowing water on Mars?
There’s a lot of evidence that there was water in the past, but we don’t have evidence of water flowing today, says Stern. She says the minerals we find are minerals that can only be made in water.
Why did Mars go wrong so terribly quickly?
“I don’t know if Mars got that wrong or if Earth was really lucky with its habitability,” Stern said.
However, Stern says, Mars has the misfortune of being smaller than Earth, which means it cools faster. Mars likely lost its internal dynamo early on that would have generated a global magnetic field that protected the Red Planet from the sun’s charged particle damage.
NASA’s MAVEN spacecraft has shown that Mars may have been stripped of its atmosphere due to the charged particles of the solar wind.
Stern says: We know that there is ice in the interior of Mars, and there may be liquid water in the interior of the Earth, but we don’t know that. On Mars it’s completely unexplored, but we know the Earth’s interior is a habitable environment, she says. Stern says there is life on Earth five kilometers deep.
Does Mars also live beneath its surface?
I think all bets are off because we haven’t been there yet, so we don’t know, says Stern. If there could be life deep on Earth, then there might be life deep on Mars, she says.