Has there ever been life on Mars? After decades of landers, rovers and orbiters, we still don’t know for sure. If there is evidence for life, it’s hiding in rocks or below ground. Some results have been tantalizing but still inconclusive. On February 21, 2023, an international research team said that obtaining evidence for life – whether ancient or current – may be even harder than thought. Their new study suggests that the science instruments currently being used on the Perseverance and Curiosity rovers may not be sensitive enough to make an accurate determination.
More powerful tools needed to find life on Mars?
Both Perseverance and Curiosity, as well as previous rovers, have already found organic material in Martian rocks. Scientists still don’t know the origin of that material, however. It could be abiotic (no life required), or from ancient organisms, or both. The problem is that the science instruments on the rovers can’t conclusively make that assessment.
Now, senior author Alberto G. Fairén of Cornell University and lead author Armando Azua-Bustos of the Center of Astrobiology (CAB) in Madrid, Spain, reaffirm this, based on studies they conducted here on Earth. The research team tested sedimentary rocks in the Red Stone Jurassic fossil delta of the Atacama Desert in northwestern Chile. Atacama is the oldest and driest desert on Earth, and in many ways serves as an analog for the surface environment on Mars. The four instruments used for the tests are either on Mars now or will be in the future.
Atacama microbes just barely detectable
The instruments did detect the microbial life present in the samples … but barely. They found multiple types of microorganisms, in fact, but couldn’t determine their classification. Scientists call this a dark microbiome. In this case, it is a mixture of both living and ancient microorganisms. However, even with state-of-the-art science tools, detecting them is very difficult. And that’s just on Earth. What about Mars? The paper says:
Our analyses by testbed instruments that are on or will be sent to Mars unveil that although the mineralogy of Red Stone matches that detected by ground-based instruments on the red planet, similarly low levels of organics will be hard, if not impossible, to detect in Martian rocks depending on the instrument and technique used. Our results stress the importance in returning samples to Earth for conclusively addressing whether life ever existed on Mars.
The chance of obtaining false negatives in the search for life on Mars highlights the need for more powerful tools.
You need to decide whether it’s more advantageous having limited capability for analysis on the surface of Mars to interrogate a wide variety of samples. Or having limited samples to be analyzed with the wide variety of state-of-the-art instrumentation on Earth.
Mars Sample Return
The science instruments on the Mars rovers are incredibly sophisticated. And moreover, in the case of Perseverance, designed specifically to look for evidence of past life. But if even those instruments can have trouble conclusively detecting that evidence, then how might they ever find proof?
The answer is to bring samples of rock and soil back to Earth – the Mars Sample Return mission – where the best labs in the world can analyze them. In fact, Perseverance has already collected 10 such samples, which NASA is planning to bring to Earth in the 2030s. That may be the only way that scientists can say for sure that those samples contain the sought-after evidence … or don’t.
Rosalind Franklin rover’s search for life on Mars
In the meantime, there is still reason to be optimistic. The European Space Agency is preparing for its Rosalind Franklin rover to launch later this decade, possibly as soon as 2028. Like Perseverance, its purpose is to look for possible life, but deeper underground. Fairén said that the rover:
… will carry a drill with the unprecedented capability of reaching down to a depth of two meters (6 1/2 feet) to analyze sediments better protected against the harsh conditions on the Martian surface. If biosignatures are better preserved at depth, which we expect, there will be more abundance and diversity, and better preservation of biosignatures, in those deep samples. Our instruments in the rover will therefore have more chances to detect them.
Bottom line: An international team of scientists says that finding conclusive evidence of life on Mars will require better tools than those on the current rovers.