Rovers sent to Mars have so far failed to detect life, probably because it does not exist on the Red Planet. But we can’t say for sure, so the search must continue, using ever-evolving methods, including this out-of-the-box idea from a team of scientists.
As detailed in a study published today in the journal Frontiers in Astronomy and Space Sciences, astrobiologists from Germany and Portugal have shown that three types of microbes are attracted to an amino acid called L-serine and will move toward it. The process, known as chemotaxis – the movement of an organism in response to a chemical – could be the basis for a simple new approach to searching for tiny extraterrestrial life in places like Mars.
“Given that the early Earth and Mars were bombarded by carbonaceous asteroids, L-serine is likely to exist on Mars,” the researchers write in their study. Previous studies have already shown that L-serine causes chemotaxis in some life forms. “If life has evolved on Mars with biochemistry similar to that known on Earth, then it is likely that L-serine could also be a powerful chemoattractant for hypothetical Martian microbes.”
Because of the extremely harsh conditions on the surface of Mars, the researchers used “hypothetical Martian microbes” known for their ability to survive in harsh environments – organisms often referred to as extremophiles. Their stand-ins were the bacteria Bacillus subtilis and Pseudoalteromonas haloplanktis, as well as the archaea Haloferax volcanii.
“Bacteria and archaea are two of the oldest forms of life on Earth, but they move in different ways and have evolved their propulsion systems independently of each other,” Max Riqueles, an aerospace engineer at the Technical University of Berlin and co-author of the study, said in a statement to Frontiers. Motor skills are the ability of a small organism to move independently. “By testing both groups, we can make life detection methods more reliable for space missions.”
For their approach to have the best chance of success on future space missions, simplicity was another important aspect of the study. Their equipment included a slide (a flat piece of glass) divided into two chambers by a thin membrane. They placed the microbes in one chamber, the L-serine in the other, and waited.
“If the microbes are alive and able to move, they will swim to the L-serine through the membrane,” explained Riqueles. Fortunately, that’s exactly what happened, suggesting that future astronauts could use this method to detect the presence of similar microorganisms in extraterrestrial samples. According to the study, this is usually difficult to achieve even with advanced microscopic techniques.
“This method is simple, affordable, and does not require powerful computers to analyze the results,” he added.
Although an automated system with smaller and more powerful hardware would have to be used to actually apply this method in future space missions, this study still highlights the potential for a cheaper and easier way to search for extraterrestrial life based on inducing microbial movement. The fact is that cheap and simple are not two words we usually hear in connection with the search for alien civilizations.
