Probing for extraterrestrials

An old biochemistry lab technique, modified by scientists at NASA’s Jet Propulsion Laboratory, could pave the way for finding life on the many icy moons inhabiting the outer solar system.

Jupiter’s moon Europa and Saturn’s moon Enceladus have been the subjects of speculation concerning extraterrestrial life for years, after scientists found evidence suggesting that they contain oceans of liquid water — believed to be necessary for Earth-like life — beneath thick crusts of ice.

Called capillary electrophoresis, the technique involves analyzing a liquid sample by running an electric current through it. The molecules in the sample separate by charge and size, and can be identified by scanning the capillary tube with a laser. The JPL research team hopes that future space missions will use their technique to identify biological molecules such as amino acids.

This new version of capillary electrophoresis can detect one molecule in less than a femtolitre of liquid — providing precision that’s more than 10,000 times better than methods currently employed by spacecraft like the Mars Curiosity rover, the researchers said.

Scientists are especially interested in using capillary electrophoresis to look for amino acids, the basic building blocks of proteins. Although hundreds of amino acids can be produced abiotically, by naturally occurring chemical reactions, only 20 of those comprise the building blocks of life on Earth.

The amino acids in our bodies are also distinctive in another way — chirality, a chemical property determined by the way an amino acid affects polarized light. While abiotic processes generate both “right-handed” and “left-handed” amino acids in equal proportion, biological processes only produce and use left-handed ones. Scientists believe that the combination of chirality and amino acid selectivity observed on extraterrestrial worlds could be strong indications for the presence of life.

Past space missions to other planets and moons have used an amino acid detection method designed for solid samples, which requires first turning the samples into a gas. The reagents used in this method need to react with water, complicating their use on icy ocean moons like Europa or Enceladus. Capillary electrophoresis also makes it easier to detect amino acids in samples with high salt contents, cutting down on the time it takes to finish analyzing a sample and making the whole process more energy-efficient.

(featured image courtesy of NASA/JPL-Caltech/SSI/JHUAPL/Univ. of Arizona)