Martian 'microbes' cover their tracks.
Kerr
R A
RA
D001419:Bacteria; D002254:Carbonates / Q000032:analysis / Q000737:chemistry; D018559:Exobiology; D005118:Extraterrestrial Environment; D052203:Ferrosoferric Oxide; D005580:Fossils; D007501:Iron / Q000032:analysis / Q000737:chemistry; D018535:Mars; D019110:Meteoroids; D010087:Oxides / Q000032:analysis / Q000737:chemistry; D013696:Temperature
D002254:Carbonates; D010087:Oxides; D007501:Iron; D052203:Ferrosoferric Oxide