MARS

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MARS

• The Red Planet

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Bulk Properties

• Radius 0.53 Earth radii
• Mass 0.11 Earth masses
• Density 3.9 g/cm3
• Semi-Major Axis 1.52 AU (1.38 1.67)
• Orbital Period 687 days (1.9 years)
• Rotational Period 1.03 days
• Mean Surface Temp 210 K (150 310)

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Long Distance Observation

• Mars is at its brightest when it is at opposition
• Appears red even to the naked eye
• In a telescope it appears to be a red disk with
  some light and dark patches
• Polar ice caps are also visible in Martian winter

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The Martian Surface

• The northern hemisphere is mostly rolling
  volcanic plains, similar to lunar maria
• The southern hemisphere consists of heavily
  cratered highlands
• The Tharsis Bulge (near the Martian equator)
  rises 10km above the rest of the surface
• Hardly any craters at all

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Volcanism

• Four very large shield volcanoes on the Tharsis
  bulge
• Largest is Olympus Mons, the largest volcano in
  the solar system
• 700km wide (size of Arizona)
• 25km high (3x higher than Mt. Everest)
• Extreme height because surface gravity is only
  40 Earths gravity
• No direct evidence of ongoing eruptions

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The Martian Grand Canyon

• Valles Marineris
• Water played no part in its formation
• Surface cracked when the Tharsis region was
  formed (tectonic fracture)
• Located on equator, nearly 4000km long
• As deep as 7 km
• Can be seen from Earth
• No further evidence of plate tectonics

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Cratering

• Marss atmosphere is thin and not efficient at
  eliminating meteoroid impacts
• Most small craters have been eroded by wind and
  dust
• Fluidized ejecta
• Ejecta blankets look as though a liquid
  splashed out of the impact crater
• May indicate a layer of permafrost just under the
  surface

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Other Evidence for Water

• Runoff Channels
• Found in the southern highlands
• Bear a strong resemblance to riverbeds
• Outflow Channels
• Found in equatorial regions
• Result of flooding long ago
• Formed tear-drop shaped islands

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Polar Ice Caps

• Two distinct parts
• Seasonal cap grows and shrinks each Martian year
• Residual cap remains permanently frozen
• Southern winter is longer and colder
  (eccentricity of Marss orbit)
• Seasonal cap is composed entirely of dry ice
  (CO2)
• During summer the CO2 sublimes and increases the
  pressure significantly
• In winter the CO2 deposits again (about 1m thick)

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Residual Polar Cap

• Northern residual cap is larger but warmer than
  the southern residual cap
• Probably the southern cap is dry ice and the
  northern cap is water ice
• Increase in water vapor in the atmosphere during
  northern summer supports this hypothesis

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The Martian Atmosphere

• Very thin
• Mostly carbon dioxide (95.3)
• 2.7 nitrogen, 1.6 argon
• Trace oxygen, carbon monoxide, and water vapor
• Temperatures are about 50 K less than Earth
• Level of water clouds and a level of CO2 clouds

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Martian Weather

• Most of the year is pretty mundane
• Sun rises, surface warms up, light winds, sun
  sets, temperature drops again
• Exciting southern summers
• Strong surface winds sweep up dust and cover most
  of the planet
• Dust can remain airborne for months

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The Interior of Mars

• Mars has almost no magnetic field
• Core is either nonmetallic, non liquid, or both
• An abundance of iron in the surface indicates
  Mars may not have differentiated in the past
• Cooled too quickly to allow for molten metals to
  proceed to the center and for plate motion to
  occur

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The Moons of Mars

• Phobos and Deimos (Fear and Panic)
• Named for the horses pulling the chariot of the
  God of War
• Small and irregular in shape
• Phobos (28km x 20 km)
• Deimos (16km x 10 km)
• Heavily cratered
• Different composition to Mars
• Orbit very close to the planet
• Phobos (9000km)
• Deimos (23000km)

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The Moons of Mars

• Both moons orbit synchronously
• Because Phobos is so close, it orbits Mars in
  less than a day (7.5 hours) and therefore rises
  in the West and sets in the East
• Densities are less than any terrestrial planet
• Probably captured asteroids