Water alteration of rocks and soils on Mars at the Spirit rover site in Gusev crater.
Gusev crater was selected as the landing site for the Spirit rover because of the possibility that it once held a lake. Thus one of the rover's tasks was to search for evidence of lake sediments. However, the plains at the landing site were found to be covered by a regolith composed of olivine-rich basaltic rock and windblown 'global' dust. The analyses of three rock interiors exposed by the rock abrasion tool showed that they are similar to one another, consistent with having originated from a common lava flow. Here we report the investigation of soils, rock coatings and rock interiors by the Spirit rover from sol (martian day) 1 to sol 156, from its landing site to the base of the Columbia hills. The physical and chemical characteristics of the materials analysed provide evidence for limited but unequivocal interaction between water and the volcanic rocks of the Gusev plains. This evidence includes the softness of rock interiors that contain anomalously high concentrations of sulphur, chlorine and bromine relative to terrestrial basalts and martian meteorites; sulphur, chlorine and ferric iron enrichments in multilayer coatings on the light-toned rock Mazatzal; high bromine concentration in filled vugs and veins within the plains basalts; positive correlations between magnesium, sulphur and other salt components in trench soils; and decoupling of sulphur, chlorine and bromine concentrations in trench soils compared to Gusev surface soils, indicating chemical mobility and separation.
Department of Earth and Planetary Sciences, Washington University in Saint Louis, Missouri 63130, USA.
Larry A
LA
Haskin
Alian
A
Wang
Bradley L
BL
Jolliff
Harry Y
HY
McSween
Benton C
BC
Clark
David J
DJ
Des Marais
Scott M
SM
McLennan
Nicholas J
NJ
Tosca
Joel A
JA
Hurowitz
Jack D
JD
Farmer
Albert
A
Yen
Steve W
SW
Squyres
Raymond E
RE
Arvidson
Göstar
G
Klingelhöfer
Christian
C
Schröder
Paulo A
PA
de Souza
Douglas W
DW
Ming
Ralf
R
Gellert
Jutta
J
Zipfel
Johannes
J
Brückner
James F
JF
Bell
Kenneth
K
Herkenhoff
Phil R
PR
Christensen
Steve
S
Ruff
Diana
D
Blaney
Steven
S
Gorevan
Nathalie A
NA
Cabrol
Larry
L
Crumpler
John
J
Grant
Lawrence
L
Soderblom
D001966:Bromine / Q000032:analysis; D002713:Chlorine / Q000032:analysis; D005118:Extraterrestrial Environment / Q000737:chemistry*; D019015:Geologic Sediments / Q000737:chemistry*; D018535:Mars; D012987:Soil / Q000032:analysis*; D013455:Sulfur / Q000032:analysis; D014867:Water / Q000737:chemistry*
D012987:Soil; D014867:Water; D002713:Chlorine; D013455:Sulfur; D001966:Bromine