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Implications for hydrologic processes on Mars from extensive bedrock outcrops throughout Terra Meridiani


Grey haematite was recently detected in the Terra Meridiani region of Mars1,2 by the Thermal Emission Spectrometer onboard the Mars Global Surveyor spacecraft. The formation of haematite on Earth often requires liquid water to be present for long periods of time, making this an important target for deciphering the history of water on Mars. The Mars Exploration Rover Opportunity landed in Meridiani early in 2004 and has since discovered light-toned bedrock outcrops rich in chemical and textural signatures of long-term water interaction locally at the landing site3. Here I use remote sensing data to show that the light-toned outcrops at the landing site are not a local phenomenon. Instead, they are observable throughout the haematite-bearing plains in both visible and thermal infrared remote sensing data. Moreover, the light-toned material outcrops around much of the margin and is mappable for hundreds of kilometres to the north, east and west of the plains. I infer that 3 × 105 km2 of this material is exposed over 20° of longitude, indicating the extended presence of surface or near-surface water over a large region of Mars.

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Figure 1: THEMIS-derived thermal inertia map of the Terra Meridiani region of Mars16.
Figure 2: THEMIS-derived thermal inertia map indexed on Fig. 1 overlaid with geomorphic unit boundaries from ref. 4.
Figure 3: Greyscale mosaic of THEMIS-derived thermal inertia indexed on Fig. 1.
Figure 4: Examples of etched terrain (E) within the haematite-bearing plains (Ph).


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I thank N. E. Putzig and M. T. Mellon for THEMIS-derived thermal inertia products used in this study and B. M. Jakosky and J. R. Zimbelman for comments on this manuscript. This work was supported by the National Aeronautics and Space Agency (NASA).

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Correspondence to Brian M. Hynek.

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Hynek, B. Implications for hydrologic processes on Mars from extensive bedrock outcrops throughout Terra Meridiani. Nature 431, 156–159 (2004).

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