Orbital identification of carbonate-bearing rocks on Mars.
Geochemical models for Mars predict carbonate formation during aqueous alteration. Carbonate-bearing rocks had not previously been detected on Mars' surface, but Mars Reconnaissance Orbiter mapping reveals a regional rock layer with near-infrared spectral characteristics that are consistent with the presence of magnesium carbonate in the Nili Fossae region. The carbonate is closely associated with both phyllosilicate-bearing and olivine-rich rock units and probably formed during the Noachian or early Hesperian era from the alteration of olivine by either hydrothermal fluids or near-surface water. The presence of carbonate as well as accompanying clays suggests that waters were neutral to alkaline at the time of its formation and that acidic weathering, proposed to be characteristic of Hesperian Mars, did not destroy these carbonates and thus did not dominate all aqueous environments.
Ehlmann
Bethany L
BL
Department of Geological Sciences, Brown University, Providence, RI02912, USA.
Mustard
John F
JF
Murchie
Scott L
SL
Poulet
Francois
F
Bishop
Janice L
JL
Brown
Adrian J
AJ
Calvin
Wendy M
WM
Clark
Roger N
RN
Marais
David J Des
DJ
Milliken
Ralph E
RE
Roach
Leah H
LH
Roush
Ted L
TL
Swayze
Gregg A
GA
Wray
James J
JJ
D005118:Extraterrestrial Environment; D058085:Iron Compounds; D008274:Magnesium; D017616:Magnesium Compounds; D018535:Mars; D017640:Silicates; D018531:Spacecraft; D013057:Spectrum Analysis; D013696:Temperature; D014867:Water
D058085:Iron Compounds; D017616:Magnesium Compounds; D017640:Silicates; D014867:Water; C005479:magnesium carbonate; C034475:olivine; C033214:Smectite; D008274:Magnesium