New Test For Life On Mars Could Help Prove We Are Not Alone In The Universe

Finding life on another planet would be a world-changing discovery for humanity. But actually detecting it is no simple task. Rovers sent to Mars by NASA have equipment to search for signs of life trapped in the rocks at the surface.

“However, the rovers’ current equipment wouldn’t be able to detect it on Mars,” Belinda Ferrari, Professor of Microbiology at UNSW Sydney, explains in a piece for The Conversation. “In samples with such scarce biomass, we use highly sensitive laboratory methods to detect microbial life, including gene sequencing and visualising cells using microscopic analysis. Prototypes for genome sequencing in the field are being developed, but they do not have the sensitivity needed for low biomass samples – yet.”

In a new study, researchers propose a method to detect signs of life in situ on the Red Planet and beyond, focusing on motility.

“Microbial motility, the directed motion of microbes under their own propulsion, can be clearly distinguished from random Brownian movement by microscopic techniques and is, therefore, a prominent biosignature of life,” the team explains in their study. “Given that it has evolved independently multiple times on Earth, motility might also be a fundamental trait of extraterrestrial life that can be exploited for its detection in a resource-depleted setting.”

Detecting motility in microbes may be something we can do easily on Earth, but less so on an alien planet. However, the team tested a way of stimulating motility in microbes. Assuming motility is universal to life, this could be a preliminary way of detecting life on the Red Planet.

“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,” Max Riekeles, a researcher at the Technical University of Berlin, explained in a statement. “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.”

The three microbes chosen by the team were selected for their hardiness, surviving in extreme environments on Earth which are closest to those found on Mars. Bacillus subtilis, a bacterium that naturally inhabits soils and the human gut, was chosen for its ability to withstand temperatures up to 100°C (212°F), while Pseudoalteromonas haloplanktis was chosen for its ability to thrive in the colder temperatures of Antarctic waters. Haloferax volcanii, the archaeon of the study, was selected for its ability to survive in highly saline environments, such as the Dead Sea.

“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.”

All three microbes studied were attracted towards L-serine, indicating that it could be a good method for finding signs of life. To simplify the process, the team used slides with two chambers separated by a thin membrane, with the sample placed in one chamber and L-serine on the other.

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

However, this would still be tricky to perform on another planet, and will require further refining if we are to use it to detect signs of life on other words.

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

The study is published in Frontiers in Astronomy and Space Sciences.