The Latest from the Mars Exploration Rovers

Spirit at Gusev Crater

Primary goal of Mars exploration: Search for water on Mars

Summary: Orbital photography shows evidence for water on ancient Mars

Also evidence for large standing bodies of water

MER Landing Sites: Gusev Crater (Spirit) and Meridiani Planum

(Opportunity)

http://marsonweb.nas.nasa.gov/landingsites/mer2003/mocs

MER Landing sites: Gusev crater (Spirit) and Meridiani Planum (Opportunity)

Landing Sites for Spirit and Opportunity

Spirit Opportunity

Mineralogy: Key to hydrological history of Mars

• Magnetite: Fe3O4

• Hematite: Fe2O3

• Olivine: Fe2SiO4

• Pyroxine: CaFeSi2O6

Minerals tell about hydrological history, what chemical reactions were occurring

Measurements of mineral structure via the Mossbauer Effect

Radioisotope selection for MER

• 57Co -> 57Fe* -> 57Fe + 14.4 keV

• Iron dominant element in rocks, good mineralogical diagnostic

• 57Co has half life of 271 days. A challenge for interplanetary missions

How does Mossbauer Effect tell you about mineral structure of Mars rocks?

Klingelhoefer et al 2003, JGR 108, E12, ROV 8

Transmission versus scattering Mossbauer Effect

MIMOS II experiment on MER

The MIMOS II Instrument

Mossbauer spectra of Mars rocks from MER

More Mossbauer spectra from Mars

Results from MER spacecraft

• Evidence of water at Meridiani from the outset: haematite chondrules, sedimentary rocks with chemically weathered compositions: “there are other possible scenarios; they all require liquid water and acidic conditions”.

• Early results from Gusev seemed to argue against water; high abundance of pristine olivine. “the ubiquitous presence of olivine in the soil suggests that physical rather than chemical weathering processes…”

Recent results from MER (cont)

• More recent results from Gusev, coatings on rock with 2-5 times high S & Cl concentrations than interior, crystalline haematite.

• “The physical and chemical characteristics provide evidence for limited by unequivocal interaction between water and the volcanic rocks of the Gusev plains”