Discoveries

The “mountains,” a misnomer that dates from the 19th century, are a heavily cratered area covered and uncovered each year by the southern seasonal polar cap. TES found the area remains cold and bright longer than other comparable areas because it is covered with unusually small grains of carbon-dioxide frost that persist longer.

Each year regional dust storms occur during the southern hemisphere summer season. Clouds of dust also appear near the edge of the polar caps prior to the onset of a regional dust storm and over the polar cap during the storms.

While Mars is a dusty planet overall, TES mapped numerous places where nighttime ground temperatures indicate bare rock or hardened sediments essentially free of dust and sand.

For three Mars years, TES operated much like a terrestrial weather satellite, making daily weather maps to track changes in atmospheric temperature, water-ice clouds, water vapor, and dust.

During southern winter, carbon dioxide gas condenses onto the polar cap as a thin slab of transparent ice. When the Sun rises in spring, the ice sublimates from the bottom of the layer, while the growing gas pressure lifts the slab off the ground. Gas then breaks through the slab in places, erupting in jets that carry dust scavenged from under the slab.

The lack of large-scale clay and carbonate mineral deposits means Mars has seen much less chemical weathering than Earth. In turn, this indicates Mars’ geologic history has been mostly cold and dry.