Meridiani Planum

MIMOS II has three temperature sensors one on the electronics board and two on the SH. One temperature sensor in the SH is mounted near the internal reference absorber, and the measured temperature is associated with the reference absorber and the internal volume of the SH. The other sensor is mounted outside the SH at the contact ring assembly. It gives the approximate analysis temperature for the sample on the Martian surface. This temperature is used to route the Mossbauer data to the different temperature intervals (maximum of 13, with the temperature width software selectable) assigned in memory areas. Shown in Fig. 3.21 are the data of the three temperature sensors taken on Mars (rover Opportunity at Meridiani Planum) in January 2004 between 12 10 PM on Sol 10 (10 Martian days after landing) and 11 30 AM on Sol 11. The temperature of the electronics board inside the rover is much higher than the temperatures inside the SH and the contact plate sensor, which are nearly identical and at ambient Martian temperature. 

Fig. 8.30 The Instrument Deployment Device (IDD) above the surface of Mars, showing all the four in situ instruments left) the MIMOS II with its contact ring can be seen in the front picture taken at Meridiani Planum, Mars right) MIMOS II is located on the left side picture taken at Gusev Crater, Mars...

Mbssbauer spectra measured by the Opportunity rover at the Meridiani Planum landing site (see Fig. 8.35) revealed four mineralogical components in Meridiani Planum at Eagle crater jarosite- and hematite-rich outcrop (see Eig. 8.34), hematite-rich soil, olivine-bearing basaltic soil, and a variety of rock fragments such as... 

Fig. 8.34 Lefty, outcrop rocks found at the crater wall of Eagle Crater, where the rover Opportunity landed on 24 January 2004. Clearly, the sedimentary structure is seen. Right) in the spectrum, taken on sol 33 (sol = Martian day) of the mission, the mineral Jarosite, an Fe -sulfate, could be identified at the Meridiani Planum landing site. It forms only under aqueous conditions at low pH (< 3 ) and is therefore clear mineralogical evidence for aqueous processes on Mars...

Meteorites on Mars. Meridiani Planum is the first Iron meteorite discovered on the surface of another planet, at the landing site of the Mars Exploration rover Opportunity [359]. Its maximum dimension is 30 cm (Fig. 8.38). Meteorites on the surface of solar system bodies can provide natural experiments for monitoring weathering processes. On Mars, aqueous alteration processes and physical alteration by Aeolian abrasion, for example, may have shaped the surface of the meteorite, which therefore has been investigated intensively by the MER instruments. Observations at mid-infrared wavelengths with the Mini-TES... 

Fig. 8.37 Left, spectrum of an accumulation of hematite rich spherules (Blueberries) on top of basaltic soil (Sol 223-228 of the mission 1 Sol = 1 Martian day). The spectrum is dominated by the hematite signal. Estimations based on area ratios (bluebeiries/soil) and APXS data indicate that the blueberries as composed mainly of hematite. Right MI picture (3x3 cm ) of hematitic spherules (blueberries) on basaltic soil at Meridiani Planum...

Fig. 8.38 (Left) The Mossbauer spectrum of the rock called Heat Shield rock, clearly shows with high intensity the mineral Kamacite, an Fe-Ni alloy with about 6-7% Ni (Right) The iron-nickel meteorite Meridiani Planum (originally called Heat Shield Rock ) at Opportunity landing site, close to the crater Endurance. The meteorite is about 30 cm across (Courtesy NASA, JPL, Cornell University)...

Klingelhofer, G. et al. 2004. Jarosite and Hematite at Meridiani Planum from Opportunity s Mossbauer Spectrometer. Science, 306, 1740-1745. 

Morris, R.V. et al. 2006b. Mossbauer mineralogy of rock, soil, and dust at Meridiani Planum, Mars Opportunity s journey across sulfate-rich outcrop, basaltic sand and dust, and hematite lag deposits. Journal of Geophysical Research, 111, E12S15, doi 10.1029/2006JE002791. 

Although the rocks in Meridiani Planum analyzed by the Opportunity rover are fascinating (see below), they are unusual. Therefore, we will focus on the rocks and soils in Gusev crater analyzed by the Spirit rover, which are spectrally similar to the bulk of the Martian crust. We will compare these compositions with those of Martian meteorites and Bounce Rock in Meridiani, which is similar to shergottites. We will also consider orbital geochemical data obtained by GRS. 

Clark, . C. plus 23 coauthors (2005) Chemistry and mineralogy of outcrops at Meridiani Planum. Earth and Planetary Science Letters, 240, 73-94. 

Rieder, R., Gellert, R., Anderson, R. C. et al. (2004) Chemistry of rocks and soils at Meridiani Planum from the alpha particle X-ray spectrometer. Science, 306, 1746-1749. 

Squyres SW, Athena Science Team (2004) Initial results from the MER Athena science investigation at Gusev Crater and Meridiani Planum. Lunar and Planetary Science Conference XXXV. Houston, TX. Abstract 2187... 

Allen, C., Probst, L.W., Flood, B.E., Longazo, T.G., Scheble, R.T. Westall, F. (2004) Meridiani Planum hematite deposit and the search for evidence of life on Mars - iron mineralization of microorganisms in rock varnish. Icarus 171, 20-30. 

Chavdarian, G.V. Sumner, D.Y. (2006) Cracks and fins in sulfate sand Evidence for recent mineral-atmospheric water cycling in Meridiani Planum outcrops Geology 34, 229-232. 

Tosca, N.J, McLennan, S.M., Clark, B.C., Grotzinger, J.P., Hurowitz, J.A., Knoll, A.H., Schroder, C. Squyres, S.W. (2005) Geochemical modeling of evaporation processes on Mars Insights from the sedimentary record at Meridiani Planum. Earth and Planetary Science Letters 240, 122-148. 

Meridiani Planum and Gusev Crater, Mars. Journal of Geophysical Research, 110, El 2S07,doi 10.1029/2005JE002451. 

Fig. 2.49 Blueberry -like spherules found in Meridiani Planum on Mars surface were analyzed by Mossbauer spectroscopy and found to be enriched in haematite, a-FejOs [86, 87]...

One of the major discoveries of the MER mission was the identification of the mineral jarosite by Mossbauer spectroscopy in S-rich, layered outcrop rocks at Meridiani Planum [90] (Fig. 2.50). Jarosite is a ferric sulphate hydroxide whose generalized formula can be written (K,Na,H30)(Fe3 xAlx)(S04)2(0H)6, where X < 1. The end members KFe3(S04)2(0H)g, NaFe3(S04)2(0H)g, and (H30)Fe3(-S04)2(0H)e are jarosite, natrojarosite, and hydronium jarosite, respectively. For... 

Jarosite is a mineralogical marker for aqueous processes because it contains the equivalent of 10 wt. % H2O in its structure as the OH anion. The average S-rich outcrop rock at Meridiani Planum has the equivalent of 2 % H2O associated with jarosite alone. An important aspect of the jarosite detection is that acidic conditions (pH < 4 at room temperature) are required for its formation. The alteration of basaltic precursor material under oxidizing, acid-sulphate conditions to form jarosite and other phases in the S-rich outcrop rocks at Meridiani Planum could have occurred under conditions provided, for example, by interactions with acid-sulphate, possibly hydrothermal waters and/or condensation of S02-rich volcanic emanations [91]. 

The past environmental conditions characterized by low pH inferred from the detection of jarosite at Meridiani Planum have implications for the suitability for life at Meridiani Planum. While microbial populations on Earth have adapted to low pH levels, they would have challenged prebiotic chemical reactions thought to have played a role in the origin of hfe on Earth [92]. 

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