Scientists used a method from ecology to identify whether icy moons could hold conditions for life |
New observatories and spacecraft missions are probing environments in our solar system that could potentially host life but have long remained hidden. Icy moons like Saturn’s Enceladus and Jupiter’s Europa likely contain oceans beneath frozen outer shells. But a layer of ice prohibits space probes from sampling them directly.
Exploring these icy moons is almost forensic: Their surfaces keep a partial record of inaccessible interiors. Scientists need tools that can help them figure out whether evidence of life lies beneath without observing it directly.
I’m a planetary scientist, and my colleagues and I have developed a tool that could help evaluate whether an environment has the right conditions for life, based on patterns in the types of molecules found in a sample.
Looking for life’s fingerprints
The search for life often begins with organic molecules: the carbon-based molecules from which life on Earth is built. Two especially important families of molecules are amino acids, which cells use to build proteins, and fatty acids, which help form cell membranes.
Yet these molecules are not unique to life – they can also form through nonbiological chemistry. Scientists have previously detected them in asteroids and meteorites.
Because detecting amino acids or fatty acids in a planetary environment alone will not tell researchers whether they are produced by life or by nonlife, they must seek additional evidence.
One clue is molecular handedness, or “chirality.” Certain amino acids occur in two mirror-image forms. Nonbiological processes often produce both forms in similar amounts, whereas life on Earth uses almost exclusively the left-handed forms. A strong excess of one form can point toward biology.
Another clue is found in the balance between........