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Mars’ Moons - Tiny compared to the planet, and orbit very close to the planet. Discovered in 1877 by Asaph Hall. They are only a few km across and are believed to be captured asteroids. The moons are irregularly-shaped and heavily cratered.
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Mars’ Moons - Tiny compared to the planet, and orbit very close to the planet. Discovered in 1877 by Asaph Hall. They are only a few km across and are believed to be captured asteroids. The moons are irregularly-shaped and heavily cratered.
Phobos is the larger of the two moons. 28 km long, 20 km wide, it has an enormous 10 km wide crater named “Stickney”.
Deimos is 16 km long, 10 km wide, its largest crater is 2.3 km across. Both moons have albedos of 0.06 or less.
Both moons have circular, equatorial orbits and synchronous rotation.
Phobos lies 9378 km from the center of Mars (less than 3 planetary radii) and has an orbital period of 7 hours, 59 minutes. As observed from Mars, it would appear to move opposite the apparent daily motion of the Sun.
Deimos is 23,459 km from the center of Mars (less than 7 planetary radii). Orbits in 30 hours, 18 minutes and takes 3 days to traverse the sky.
No seismic studies have been done on Mars. Mars has no magnetic field; therefore it has a nonmetallic core, or the core is not liquid, or both.
Surface Appearance -Viking I landed in Chryse Planetia, east of the Tharsis Bulge. Viking II landed in Utopia Planetia. Both found fine-grained soil and rock-strewn plains.
Chemical analysis of the soil indicates that the surface soil is iron-rich. The oxygen in the atmosphere causes the surface iron to “rust”. This is what gives Mars its red color.
Mars’ atmosphere is 95% CO2. The air pressure is only 1/150 of Earth’s. The air is 10,000 times thinner than the air on Venus.
It would be too thin to breathe, even if it was the right composition.
Weather - The surface temperature is 50K cooler than Earth. The early morning cool temperatures produce water-ice fog in the Martian canyons.
In the southern summer strong surface winds sweep up dry dust. This can flood the atmosphere with dust which stays airborne for months at a time.
These dust storms can reach heights of 20 to 30 km. The upper level winds can reach speeds of 150 km/hr. These are probably convection currents caused by ground heating.
Polar Ice Caps –Each cap consists of a seasonal cap, which grows and shrinks each Martian year, and a residual cap, which remains permanently frozen.
The Southern Cap is 4000 km across at its largest. The Northern Cap is 3000 km across at its largest. The southern cap is larger because of the eccentricity of Mars’ orbit.
During southern winter Mars is considerably farther from the Sun than it is during northern winter, so the southern seasonal cap can grow larger.
The seasonal caps are almost entirely CO2. The maximum thickness of the seasonal caps is about one meter.
The southern residual cap is 350 km across, and is mostly made up of CO2 (maybe some H2O). Its temperature is always below 150K.
The northern residual cap is 1000 km across. The temperature can exceed 200K. It may be mostly H2O ice.
The thickness of the residual caps is unknown. It may be only a few km.
The 50K difference in temperature between the north and south caps is probably due to the dust storms carrying heat from the south to the north during southern summer.
This is six months of heat and dust transfer. The northern ice cap becomes dustier, absorbing more sunlight.
This probably causes the sand dunes found in the northern polar terrain of Mars.
Recently a meteorite from Antarctica was examined and found to contain what might be fossils of bacteria. The composition of this rock suggests that it originated on Mars. Of course, this would indicate the presence of primitive life on Mars.
