Identifying Extraterrestrial Life Through Its Escape Responses: A Bold Gamble or a Stroke of Genius?

Movement as a biosignature

From the 1960s, some researchers had suggested that motility could serve as a biosignature – a reliable index of the presence of life. But at the time, the technology on board landingers did not make it possible to precisely observe the movement of microbes. Today, the progress in computer science and artificial intelligence change the situation. In a laboratory of astrobiology, a researcher and his team developed a system of visual analysis which distinguishes the voluntary movements of the microbes of the simple random movement of the particles, called the Brownian movement.

Their automatic learning algorithms reach an accuracy of more than 99 % to identify an intentional movement. It is a real advance, because it means that it is finally possible to detect a biological activity, and therefore potentially life, on another planet.

Test the limits of life

To go further, the researchers submitted bacteria like E. coli on conditions close to those reigning on the surface of Mars: salty environment, extreme temperatures, lack of nutrients. The result? The microbes react. Exposed to high concentrations of sodium perchlorates, substances, however toxic for most cells, some microbes have started to speed up their movement during a short period of time. As if they were trying to flee an environment that has become too hostile.

This ability to move away from a stress zone is a strong signal: it could constitute tangible proof of the presence of life, capable of reacting to its environment.

Stimulate microbes to better see them move

But there is a downside. In some cases, microorganisms prefer not to move at all and wait for a more favorable environment. To get around this problem, the team has tested different types of stimulation: light, magnetic fields, or chemical attractors such as le-Sérine, an amino acid. The latter has systematically attracted different microbial species, including bacteria as Bacillus subtilis Or Pseudoalteromonas haloplanktisas well as an extreme archaeon (Haloferax Volcanii).

This type of approach, in addition to being effective, is very compact and easily integrated into a spatial mission. It would make it possible to design an uppercase instrument, embarked on a Martian landing, to test the motility in situ.

Credits: Wildpixel/ISTOCK

Take water with you

It remains to resolve a major constraint: liquid water, essential to observe the displacement of microbes. As it is rare, even absent on the surface of March, the idea would be to take some drops and place them on samples of Martian soil. The other option is to target particularly promising regions:

• The high lands of the South,
• Valles Marineris funds,
• Or the interior of Martian caves, where pressure would allow salt water to subsist.

A useful method also on earth

Interestingly, this technology would not only be used to explore Mars. It could also be used to detect pathogens in water on earth, such as cholera bacteria, responsible for millions of deaths each year in developing countries. The researchers have already managed to simulate their characteristic movements and identify them.

By extending this approach, it would be possible to identify other pathogens such as Salmonella Or Legionellaor even adapt the technique to other biological liquids such as blood.

Towards a future where we “see” life move

In short, motility could well become one of the most robust keys to detect life elsewhere. Not only is this approach based on fundamental behavior of the living, but it is also reproducible, observable and now measurable with precision thanks to AI. From the red planet to our earthly waters, the same strategy could soon revolutionize our way of seeking life.

And maybe one day, looking at a drop of water sliding on a Martian blade, we will see the proof that we are not alone.