Finding alien life may be as simple as watching microbes move

What if the key to extraterrestrial life isn’t hidden in the vastness of the cosmos, but in the tiny movements of microbes? The search for life beyond Earth has captivated humanity for generations, fueling both science fiction adventures and serious space exploration.

One intriguing approach is to observe the spontaneous movement of microorganisms – a key indicator of life. When specific chemicals trigger this movement, the phenomenon is known as chemotaxis.

Alien life detection with microbes

Researchers in Germany have now developed a simplified method to induce chemotactic movement in some of Earth’s smallest life forms. Ultimately, learning how microbes move could make the detection of alien life more efficient.

“We tested three types of microbes – two bacteria and one type of archaea – and found that they all moved toward a chemical called L-serine,” said Max Riekeles, a researcher at the Technical University of Berlin.

“This movement, known as chemotaxis, could be a strong indicator of life and could guide future space missions looking for living organisms on Mars or other planets.”

Microbes that defy extremes

The microorganisms selected for the study are known for their resilience in extreme conditions.

Bacillus subtilis, highly motile in its spore form, can endure temperatures up to 100°C (212°F). Pseudoalteromonas haloplanktis, isolated from Antarctic waters, thrives between -2.5°C (27.5°F) and 29°C (84.2°F).

Meanwhile, the archaeon Haloferax volcanii is adapted to the high-salinity environments of the Dead Sea.

“Bacteria and archaea are two of the oldest forms of life on Earth, but they move in different ways and evolved motility systems independently from each other,” Riekeles explained. “By testing both groups, we can make life detection methods more reliable for space missions.”

The amino acid L-serine, which has been shown to trigger chemotaxis in various life forms, was used to stimulate movement in the microorganisms.

Scientists speculate that if extraterrestrial life exists on Mars and shares biochemical similarities with Earth life, Martian microbes could also be attracted to L-serine.

Simple method for alien life detection

The study revealed that L-serine acted as an attractant for all three species.

“Especially the usage of H. volcanii broadens the scope of potential life forms that can be detected using chemotaxis-based methodologies, even when it is known that some archaea possess chemotactic systems,” Riekeles explained.

“Since H. volcanii is thriving in extreme salty environments, it could be a good model for the kinds of life we might find on Mars.”

To achieve this, the researchers used a straightforward technique which included a slide with two chambers separated by a thin membrane. The microorganisms were placed on one side, while L-serine was introduced on the other.

“If the microbes are alive and able to move, they swim toward the L-serine through the membrane,” Riekeles explained. “This method is easy, affordable, and doesn’t require powerful computers to analyze the results.”

Achieving more with fewer resources

For this technique to be used on extraterrestrial life-detection missions, however, certain modifications will be necessary.

“Smaller and more robust equipment that can survive the harsh conditions of space travel and a system that can work automatically without human intervention are two of them,” noted the researchers.

Once these challenges are addressed, microbial movement could help uncover life in unexpected corners of the cosmos – perhaps even in the subsurface ocean of Jupiter’s moon Europa.

“This approach could make life detection cheaper and faster, helping future missions achieve more with fewer resources,” concluded Riekeles. “It could be a simple way to look for life on future Mars missions and a useful addition for direct motility observation techniques.”

Future research directions

The implications of this research extend beyond Mars. If chemotaxis can serve as a universal biosignature, future missions could deploy similar methods to detect life in other extraterrestrial environments.

Europa, Enceladus, and Titan – with their subsurface oceans and organic-rich chemistry – are prime candidates for exploration.

Chemotaxis-based detection could be particularly useful in missions targeting icy moons, where microbial ecosystems may exist beneath thick ice layers.

These environments pose challenges for direct observation, making indirect detection methods like chemotaxis especially valuable.

This new approach could also complement existing life-detection techniques, such as atmospheric biosignature analysis and organic molecule detection.

By integrating multiple strategies, scientists can improve the reliability of extraterrestrial life detection and refine future astrobiology missions.

As space agencies plan the next steps in the search for alien life, this simplified test on the movement of microbes could become a key tool in identifying signs of life beyond Earth.

The full study was published in the journal Frontiers in Astronomy and Space Sciences.

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