Surface topography

Altimetry based on the column density of carbon dioxide measured by the infrared photometer in the 2.06 micron absorption band was obtained along the orbiter tracks across the surface. The inferred altitudes were in general agreement with terrestrial radar observations.

Surface properties

The large diurnal variations of surface temperature indicated a low’ heat conductivity characteristic of a dry and dusty surface. Latitudinal surface temperature variations ranged from -110°C at the northern polar cap to + 1VC near the equator. Hquatorial temperatures averaged -40°C, and at 60°S latitude they were -70°C without much diurnal variation. Dark areas on the surface were 10 to 15 degrees warmer than the light areas. The surface cooled rapidly during the night in low latitudes, indicating a dry, porous soil with a low thermal conductivity. Subsurface temperatures down to a depth of 0.5 meter were no higher than -40°C. There were thermal ‘hot spots’ some 10°C warmer than their surroundings. Temperatures at the northern polar cap were close to the carbon dioxide condensation temperature. Surface pressures of 5.5 to 6 millibars ‘лете measured. Soil density, heat conductivity, dielectric permeability and reflectivity were derived from microwave and thermal radiometry. Soil densities of 1.2 to 1.6 g/cc were reported, with values increasing to

3.5 g/cc in some places. The surface was presumed to be covered with silicon dioxide dust to an average depth of about 1 mm. Heat flow anomalies on the surface were discovered.

Global properties

Global data on the Martian gravity and magnetic fields was acquired. No intrinsic planetary magnetic field was detected, and plasma data for the interaction of the ionosphere with the solar wind indicated a magnetic moment at least 4,000 times weaker than that of Earth. A key discovery were large local mass concentrations in the gravity field, similar lo Ihose of the Moon, which created significant changes in the orbits of the spacecraft. In addition, the polar diameter was measurably less than that at the equator.

Landers:

Although the Mars 2 lander crashed, it is significant as the first human artifact to reach the surface of Mars.

The Mars 3 lander gained the distinction of being the first successful landing on Mars, but it fell silent almost immediately. Figure 12.19 shows the data returned by

the scanning-photometer imager, released in recent years, which analysis indicates to be mostly noise.