The Latest Distribution of Hematite in Sinus Meridiani
and Daytime Temperature Images

Figure 1: Example TES Spectra

These spectra are examples of what TES spectra look like before they are calibrated to remove atmospheric contributions. The spectrum of water-ice clouds is dominated by an absorption near 800 cm^-1 (12 microns) and a smaller band near 200 cm^-1 (50 microns). The spectrum of dust shows absorptions due to silicate minerals (minerals all containing SiO₂) in the atmosphere, and the third spectrum shows the combined signatures of dust and water-ice clouds. The last spectrum looks a lot like the dust spectrum, but it displays subtle differences that indicate that we are seeing a surface component as well; the emissivity in the long wavelength regions (20-50 microns, or 500-200 cm^-1) is lower than that in the dust-only spectrum. This additional absorption is due to surface minerals with lower emissivities than the atmospheric dust.

Figure 2: Additional Details on the Distribution of Crystalline Hematite

This revised image of the "hematite region" in Sinus Meridiani shows the distribution of hematite as mapped during the aerobraking phase of the MGS mission (large pixels, slanted to the right) as well as new data collected during the mapping phase. The new data (small pixels, slanted to the left) are helping to delineate the boundaries of this interesting deposit.

Figure 3 and Figure 4. Daytime temperature images

These figures show daytime Martian surface temperatures. The warmest temperatures are shown in white (~0 C) and the coldest in purple (~ -130 C). During the day, surface temperatures are similar in the mid-latitudes of the planet, regardless of albedo, in contrast to nighttime temperatures. This difference is a result of the differing thermal properties of the surface materials, which are emphasized at night. Small particles lose their heat quickly at night, while rocks stay warmer longer. The view in Figure 3 shows the large extent of the winter south polar cap. The white area near the equator on the right side of the image is Syrtis Major, a low albedo feature on the surface. Below Syrtis Major is a semi-circular region of cooler temperatures that are in the northern portion of the Hellas basin. A triangular white area to the left of Syrtis Major is another low albedo region, Sinus Meridiani. Figure 4 shows the warmer north polar region, where it has been summer and is now approaching the fall season. Slightly cooler (redder) round features in the equatorial region slightly left of the center of the image are the high-elevation Tharsis volcanoes.

The TES instrument was built by Santa Barbara Remote Sensing and is operated by Philip R. Christensen, of Arizona State University, Tempe, AZ. The MGS mission is managed for NASA by the Jet Propulsion Laboratory, Pasadena CA.

Contact: Phil Christensen, Arizona State University; (480) 965-1790

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