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Projects: Mars Climate Sounder Team WebsiteFirst Views of Mars from Mars Climate SounderData acquired March 24, 2006
The data for these images were captured just two weeks after Mars Reconnaissance Orbiter arrived in Mars orbit. The spacecraft was then in a highly elliptical orbit and stood about 45,000 kilometers (28,000 miles) from the planet when Mars Climate Sounder performed these observations -- a distance about 150 times greater than the distance of its nominal science orbit. Four scans of Mars Climate Sounder's 21-element arrays were necessary to cover the full globe of Mars. Data from the four scans were mosaicked into these views, leading to some visible horizontal seams. Data were captured in all nine of Mars Climate Sounder's channels, each one sensitive to a different range of the electromagnetic spectrum. The channels are numbered A1 to A6 and B1 to B3.
Channel A6 can see reflected sunlight in the visible and near-infrared part of the spectrum (0.3 to 3 microns). Because the view is from Mars' north pole during northern summer, only a little more than half of the globe of Mars is illuminated at these wavelengths. Surface ice and atmospheric hazes reflect sunlight to space, so they appear bright. During the science phase of the mission, views through Channel A6 will track how the amount of solar energy reflected from Mars varies from place to place and season to season, particularly in the polar regions where absorbed sunlight vaporizes the seasonal carbon dioxide ice. All of the other channels on Mars Climate Sounder capture light in the thermal infrared part of the electromagnetic spectrum. In wavelengths from about 10 to about 50 microns, Martian materials radiate heat energy to space. This heat radiation happens whether Mars is sunlit or not, so the entire globe of Mars (even the night side) is visible in the remaining images. However, temperatures are generally warmer on the day side. All of the images are calibrated to the same temperature scale.
Channel A4 spans 11.5 to 12.2 microns and will be used to track dust and clouds in the atmosphere. In the current season on Mars, the atmosphere is relatively clear except for an equatorial belt of thin water-ice clouds, so this view is dominated by the infrared radiation from the surface on the relatively hot day side (upper right). Channel A3 spans 15.0 to 15.7 microns, a wavelength range where carbon
dioxide in Mars' atmosphere is an absorber. As a result, radiation from
the surface and lower atmosphere is not reaching the view of Mars Climate
Sounder. The radiation comes from higher altitudes, above 25 kilometers
(15 miles), where the atmosphere is quite cold, and where there is not much
temperature difference between the night side and the day side of the planet.
The polar atmosphere is colder, so it appears darker. Channels A2 and
A1 span 15.5 to 16.3 and 16.3 to 16.8 microns, respectively. These
track to longer wavelengths from the carbon dioxide absorption sampled by
channel A3, so they probe the temperature progressively deeper into the atmosphere. From
channel A3 to A2 to A1, the temperature warms as you approach the surface,
and there is more variability from place to place. However, at all
channels, the north pole remains a solidly cold spot.
Channels A5 and B1 span 20.0 to 25.0 and 29.4 to 34.5 microns and will be used to track dust and clouds as well as to study temperatures in the lowermost part of the atmosphere. Like channel A4, most of the variation is due to surface temperatures, with the hottest temperatures being on the day side and the coldest at the north pole. Finally, channels B2 and B3 span 38.5-45.4 and 40.8-43.5 microns. They are intended to allow the Mars Climate Sounder team to determine the abundance of water vapor in the atmosphere, but further processing will be required before that information can be teased out of the data. These wavelengths are also sensitive to dust and clouds in the atmosphere. Three of the nine images from this set were originally released on March 31, 2006. These views contained noticeable "steps" in the edge of Mars' disk, and Mars appeared noticeably flattened. These first images, released quickly after Mars Reconnaissance Orbiter's arrival at Mars, were a quick-and-dirty data product that did not precisely account for the geometry of Mars Climate Sounder's view of Mars. The images above employ the correct geometry, so Mars appears to be the right shape -- round!
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