Albedo of Mars's Southern Seasonal Cap in Mid-Spring at 1.08 micron (Continuum)
This map is a mosaic from ten OMEGA observations between LS 221.6° and 224.4°. The albedo is evaluated assuming a perfectly diffusive surface (Lambert albedo). The grey scale extends from an albedo of 10% (black) to 80% (white). The seasonal cap appears similar to that observed by Mars Global Surveyor (MGS) at LS 220° in 1999.
Over part of the image, a false colour scheme is implemented, with each of the three colour channels remaining proportional to the reflectance factor at 1.08 μm:
- the red channel is enhanced proportionally to the CO2 band depth at 1.43 μm
- the blue and green channels are enhanced proportionally to the H2O ice band depth at 1.5 μm
The low albedo region within the cap very closely matches the cryptic region observed by the Thermal Emission Spectrometer (TES) on board MGS in 1999. Most of the seasonal cap is spectrally dominated by CO2 ice (reddish tones), with very bright regions (a: 345° E, 86.2° S, albedo 80%) and less bright regions with much stronger CO2 ice signatures (b: 68° E, 73° S, albedo 42%).
The seasonal cap is compositionally very heterogeneous between longitudes 60° E and 220° E. Relatively bright streaks (albedo >40%) are spectrally dominated by either CO2 ice (reddish tones) or H2O ice (bluish tones; for example, region c at 200° E, 72.8° S).
Within the cryptic region itself, defined by albedos <30% at latitudes higher than 70° S, signatures of both CO2 ice and H2O ice are much weaker than those observed in other areas of the seasonal cap. A representative area (80° E, 82.5° S), with an albedo of 25%, is labelled d.