Will we EVER find signs of life on Mars? Scientific instruments lack sensitivity, study warns

The instruments scientists use to find signs of life on Mars may not be sensitive enough, a study has found.

Researchers from the Autonomous University of Chile have tested the advanced gadgets used by NASA’s Curiosity and Perseverance rovers in the Atacama Desert.

While lab equipment identified biosignatures — molecules that indicate the existence of life, past or present — in the samples, locating them using rover technology proved “hardly possible.”

This suggests that the lack of results so far obtained during missions on the Red Planet could be a result of the instruments, rather than what is in the samples.

“Our results highlight the importance of returning samples to Earth to definitively determine whether life ever existed on Mars,” the authors wrote.

Since the 1970s, scientists from all over the world have been scanning the surface of Mars for signs of life.

This began with the Viking Lander missions, which took samples from the Martian soil to search for carbonaceous “organic” molecules.

Carbon is a primary component of all known life on Earth, so molecules containing it act as potential biosignatures.

Other missions over the years include Mars Pathfinder, which brought the first rover to the planet, and the Spirit and Opportunity rovers that searched for water.

Today, the Perseverance rover roams a delta of Mars collecting interesting samples that it hopes to return to Earth.

However, so far none of these missions have yielded any indisputable evidence of extraterrestrial life, which the researchers speculated may not actually be due to its absence.

“We hypothesize that current instrument limitations and the nature of organics in Martian rocks may also hinder our ability to find evidence of life on the red planet,” they wrote.

For their study, published today in Nature communicationthey carefully inspected soil samples at Red Stone, a more than 100 million-year-old river delta in the Atacama Desert.

Known as the most ‘Mars-like’ area on Earth, this accurately mimics the harsh, irradiated environment.

Red Stone soil is often exposed to water vapor through fog, allowing microbial life to exist within it.

The researchers first examined samples using lab techniques and equipment, giving them a complete picture of what biosignatures were present.

They found that most of them could be considered “microbial dark matter” — from species that have yet to be formally described.

They then analyzed samples using instruments, or similar versions of them, that had been sent to the Red Planet in the past or are currently there.

The first was one similar to the “Sample Analysis on Mars” instrument, or SAM, currently aboard the Curiosity rover, but 10 times more sensitive.

Initially, it turned out to be “hardly possible” to identify organic molecules known as alkanes, as the signals were obscured by the noise from the minerals.

“The fact that alkanes were detected at the detection limit of the commercial instrument used indicates that they may not be detectable with the SAM flight model,” the authors wrote.

Only when the sample underwent a chemical treatment that made the organic molecules in it easier to detect were they picked up by the SAM-like tool.

These include proline, an amino acid that could have been produced by the bacteria in the sample.

While this suggests that the real SAM could have detected them as well, it would depend on their abundance and the instrument’s settings.

Second, they analyzed the sample using the “Mars Organic Molecular Analysis,” or MOMA — an instrument that will be on board the European Space Agency’s ExoMars rover.

It was supposed to be deployed to the Red Planet this summer, but the launch was postponed due to the war in Ukraine.

The MOMA uses ‘flash pyrolysis’ – where an organic sample is heated rapidly in the absence of oxygen to break it down into detectable components.

However, it couldn’t detect organic molecules in the Red Stone soil sample unless it first underwent the same chemical treatment as with the SAM-like instrument.

Even then, only a few were picked up, showing that “most Red Stone samples contained organic levels below MOMA detection limits.”

The authors say these results also demonstrate the “critical importance” of testing instruments in Mars-like environments on Earth before launching them.

Finally, samples were analyzed using ‘SOLID-LDChip’, a technology designed to search for Martian biosignatures, but there are no current plans to deploy it.

This provided some evidence of bacteria, including certain species not currently living in Red Stone soil.

The authors say this suggests that the river delta “million years ago had enough water to support photosynthesis, but no longer as the Atacama became drier over time.”

This result makes SOLID-LDChip a “promising technique for detecting microbial life…although microorganisms present on Mars in concentrations lower than those found in Red Stone may still be undetectable.”