Life isn't just where you find it, but how you find it. Because any extraterrestrial life in the Solar System may be very rare, NASA's Jet Propulsion Laboratory (JPL) in Pasadena is looking at a new technique that is 10,000 times more sensitive than the ones used in the current generations of deep space probes. Called capillary electrophoresis, it's especially well suited for seeking life in the buried oceans of Jupiter and Saturn's moons.

The search for life in our Solar System is a major priority for NASA, but as we learn more about the nature of the other planets and moons, it's becoming apparent that if life does exist, it will be in the form of very simple, very rare microorganisms. This is because even though signs of liquid water have been found on Mars and in the subsurface oceans of the various ice moons of the Solar System, most of this water is filled with salts or alkali similar to the Dead Sea or Mono Lake, California. Life exists in these venues, but is rarer than in fresh or less saline water, so more sensitive tests are needed to find it.

In a new study, a JPL team discusses using capillary electrophoresis as a way of detecting signs of life, a method that is several orders of magnitude more sensitive than the ones currently used by spacecraft like Curiosity. According to JPL, the technique, which was first developed in the 1980s, is not only more sensitive, but also simpler, which is always a plus in space engineering.

Mono Lake, California is similar to some environments in the Solar System where life may exist(Credit: NASA/Mono County Tourism)

Capillary electrophoresis involves mixing a liquid sample, such as seawater, with a liquid reagent. This solution is then subjected to an electrical field that causes the various molecules in the mix to separate at different speeds. Using laser-induced fluorescence detection, scientists can measure this separation speed and deduce what the solution is made of. JPL says that this is the first time this technique has been adapted for searching for extraterrestrial life on an ocean world.

"Our method improves on previous attempts by increasing the number of amino acids that can be detected in a single run," says Jessica Creamer, a postdoctoral scholar at JPL. "Additionally, it allows us to detect these amino acids at very low concentrations, even in highly salty samples, with a very simple 'mix and analyze' process."

The JPL researchers used the technique on samples from Mono Lake, where they looked for 17 different amino acids that are commonly found on Earth and may exist in other places in the Solar System. One clever twist is that they also differentiated between amino acids from non-living sources by seeking signs of "chirality" or handedness – amino acids come in right and left-handed structures like gloves. Amino acids from non-living sources can be either handed, but ones from living sources tend to be overwhelming one or the other. The team believes that the same will be true off-planet.

"One of NASA's highest-level objectives is the search for life in the universe," says principal investigator, Peter Willis of JPL. "Our best chance of finding life is by using powerful liquid-based analyses like this one on ocean worlds."

The research was published in the journal Analytical Chemistry.

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