A promising (and surprisingly simple) way to detect alien life
A promising (and surprisingly simple) way to detect alien life
By Dirk Schulze-Makuch | Published: 2025-01-17 16:41:00 | Source: Hard Science – Big Think
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The central question for astrobiologists — researchers who, like me, explore the possibility of extraterrestrial life — seems deceptively simple: What is the best way to detect and learn about life?
So far, we’ve only been able to launch one spacecraft mission dedicated to this problem: The decline of the Vikings in the 1970s. The results of the Viking experiments in biology were generally thought to be inconclusive, and their interpretation remains controversial today. But what has become clear over the past 50 years is that new methods are needed that can more specifically distinguish between soil samples with living and non-living content. One of the most promising of these methods relies on the motility of microbes, that is, their ability to move in a liquid medium.
Movement
The movement has actually been proposed as a “biosignature.” Early 1960sBut at the time, technology was not advanced enough to perform automated microscopic observations on the Mars lander. Today’s more powerful minicomputers make this an option Not only on Mars but also on the icy moons of the outer solar system.
The work being done in my laboratory to develop locomotion as a means of detecting life is headed by Max Riklis, an applied engineer Algorithms to track the movement of microbes in liquid water Using machine learning algorithms, we were able to distinguish between microbial movement and the random movement of inorganic particles (such as sediment grains) Accuracy greater than 99%. (This random movement is called… Brownian motionIt results when molecules collide with each other, which often happens as temperatures rise.)
We have continued this research in the past few years by exposing microbes to Mars-like conditions and using stimuli to initiate movement. in New paper, we report How distinctive movement patterns of Escherichia coli Bacteria changed when exposed to different harsh environments, especially high-salt solutions of the type found on Mars.
Interestingly, we observed a short-term increase in bacterial motility at certain salt concentrations, especially with sodium chlorate and sodium perchlorate, which are cytotoxic. We interpret this as an effort by the organism to move away from stressful high salt concentrations. Given that bacteria are already known to navigate harsh and variable environments, this is a key biosignature for identifying life on Mars.
There’s a problem, though. It can be difficult to get microbes to start moving away from stressors in the first place. They often like to sit around waiting for better times, which means returning to benign environmental conditions with plenty of food. To overcome this trend, our group has been experimenting with microorganisms while also stimulating movement, which can be done by stimulating them with light, electric, or magnetic fields, or certain chemicals. We used the amino acid L-serine as bait and found that all of the organisms tested were two different bacteria (Bacillus subtilis and Pseudohaloplankton(and one effect)Haloferax volcanicum) – will move towards L-serine. We think this type of approach would be well-suited to experiment with detecting life on another planet because the setup is so small and easy to embed in a spacecraft.
One of the big problems facing the life-detection mission is finding a place where the lander can reach, but where there may also be liquid water near the surface. We could get around this by taking water with us on the landing mission, exposing Martian soil to a drop or two, and then seeing if microbes move around in the liquid. Otherwise, we have to identify potential habitats where water already exists. These may include brines that exist only at very low temperatures and for short periods, or environments containing sodium chloride-rich salt rocks that allow microbes to draw life-sustaining water from the atmosphere. The southern highlands of Mars will meet these conditions. A third possibility is to land in topographically low places such as the floor of Valles Marineres or inside caves, where atmospheric pressures are sufficient to support liquid (salty) water.
While we believe our approach can help distinguish life from non-life on Mars, we have been less successful at distinguishing the different microbes tested from each other. Here we have achieved only 82% accuracy so far. However, some microbes are easier to identify than others, specifically pathogens, because they move very quickly and thrive at certain preferred temperatures.
Terrestrial applications
This leads to another potential application. We were able to simulate the movements of cholera bacteria in water and identify them by their distinctive movement patterns. Waterborne pathogens such as cholera pose a huge health problem, especially in developing countries, and cause the death of more than three million people every year. We are developing tools to detect cholera bacteria in water and hope to expand this technology to other pathogens such as salmonella and strep. Future applications may be able to detect pathogens in other fluids such as blood.
Once again, technology developed for space exploration may have great value here on Earth.
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