Never touted as easy, hunting for aliens just got a little bit harder.
It seems an excess of "left-handed" molecules, long assumed to be a signature of life, can be created inside asteroids through a non-biological process. That puts a damper on missions that intended to look for this chemical signature as evidence of biological activity on other worlds.
Molecules have handedness, or chirality, if their mirror-images cannot be superimposed upon each other, rather like your right and left hands. Life on Earth is built almost exclusively on left-handed amino acids, so scientists have assumed that a strong left-handed bias is a fundamental part of biochemistry.
Instruments on the European Space Agency's ExoMars and Rosetta missions are designed to search for an excess of left-handed molecules as an indicator of life.
But a new study found that meteorites collected from Canada's Tagish Lake also have a excesses of left-handed aspartic and glutamic acids, two amino acids that are common in terrestrial life.
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