Physics
Scientific paper
Nov 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998eostr..79..533k&link_type=abstract
EOS, Transactions, American Geophysical Union, Vol. 79, p.533
Physics
Mars, Remote Sensing, Polar Regions, Thermal Spectroscopy
Scientific paper
During the initial aerobraking and science phasing orbit period, Mars Global Surveyor (MGS) periapsis was at high northern latitudes and hence Thermal Emission Spectrometer (TES) observations of the polar regions were of different nature in the two hemispheres. In the south (spring and summer), observations were regional (all times of day poleward of 60S) and resolution was typically 50-100 km. In the north (fall and winter) observations are largely nadir tracks with 5-10 km resolution. Overall, the recession of the south cap was similiar to that observed by Viking; with the appearance of a dark interior collar near L_s 208, becoming strongly assymetric in late summer, and the Mountains of Mitchell being significantly retarded for their latitude. We have mapped the date of most rapid temperature increase (which we term the ``crocus'' date); we consider this to be near the time when the last surface CO_2 disappears. Use of such a seasonal marker allows comparison of the evolution of surface conditions between sites with different seasonal schedules. One 600x1500 km area (approx. 72-80 S, 180-250 W) transitions to low albedo [lambert] and then brightens again well before its crocus date. Because bare soil will warm rapidly at this season, the apparent albedo change must be due to some change of the CO_2 reflectance properties, which we attribute to CO_2 ice, versus frost or snow, becoming exposed at the surface. Using the apparent bolometric albedo and spectral emission (corrected for atmospheric effects) and a representative sub-surface soil model, we have calculated the latent heat of sublimation inventory needed to reproduce the TES springtime observations; this yields a lower bound on the amount of solid CO_2 seasonal deposit. North polar observations are largely in the dark; the brightness temperatures generally agree with the expected CO_2 saturation temperature at the surface; the radiance near 18 microns seems to be the best indication of surface kinetic temperature. Transitory ``cold spots'' have been observed where the longer-wavelength brightness temperatures drop as low as 115K. Based upon similiarity of TES spectra to theoretical emission spectra of fine-grained CO_2, we tentatively explain these features as fine CO_2 cirrus or very fine surface snow.
Kieffer Hugh H.
Mullins F.
Titus Timothy
No associations
LandOfFree
TES pre-Mapping-Phase Polar Observations does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with TES pre-Mapping-Phase Polar Observations, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and TES pre-Mapping-Phase Polar Observations will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1075376