cr9b00474_si_liveslides.zip (6.85 MB)
The Search for Chiral Asymmetry as a Potential Biosignature in our Solar System
online resource
posted on 2019-11-25, 20:03 authored by Daniel P. Glavin, Aaron S. Burton, Jamie E. Elsila, José C. Aponte, Jason P. DworkinThe search for evidence of extraterrestrial life in our
Solar System
is currently guided by our understanding of terrestrial biology and
its associated biosignatures. The observed homochirality in all life
on Earth, that is, the predominance of “left-handed”
or l-amino acids and “right-handed” or d-sugars, is a unique property of life that is crucial for molecular
recognition, enzymatic function, information storage and structure
and is thought to be a prerequisite for the origin or early evolution
of life. Therefore, the detection of l- or d-enantiomeric
excesses (ee) of chiral amino acids and sugars could
be a powerful indicator for extant or extinct life on another world.
However, studies of primitive meteorites have revealed they contain
extraterrestrial amino acids and sugar acids (aldonic acids) with
large enantiomeric excesses of the same chirality as terrestrial biology
resulting from nonbiological processes, complicating the use of chiral
asymmetry by itself as a definitive biosignature. Here we review our
current knowledge of the distributions and enantiomeric and isotopic
compositions of amino acids and polyols found in meteorites compared
to terrestrial biology and propose a set of criteria for future life
detection missions that can be used to help establish the origin of
chiral asymmetry.