Early life thrived despite earthly travails.
Kerr
R A
RA
D001272:Atmosphere; D018534:Earth, Planet; D005057:Eukaryotic Cells / Q000502:physiology*; D019605:Euryarchaeota / Q000502:physiology; D019419:Evolution, Planetary; D005580:Fossils; D018535:Mars; D008697:Methane / Q000737:chemistry / Q000378:metabolism; D000069497:Origin of Life; D010100:Oxygen / Q000378:metabolism; D011387:Prokaryotic Cells / Q000502:physiology*
D008697:Methane; D010100:Oxygen