Terrestrial Planetary Geology: Mars

1
Terrestrial Planetary GeologyMars
2
MARS

• Earths Little Brother
• The Mostly Likely Place to Find Extraterrestrial
  Life

3
Basic Martian Properties

• Mass is 0.106 that of Earth (via Phobos Deimos)
• Radius is 3394 km or 0.53 of Earth (angular
  diameter at opposition) Density is 3.93
  g/cm3 or 0.71 of Earth ?a different interior
  from Earth, Venus or Mercury.
• As seen from Earth, Mars is Closest at
  opposition some details visible from Earth.
• Much fainter than Venus further from Sun,
  smaller and lower albedo (.15 vs .70) all make
  Mars fainter.

4
Mars Orbit
5
Martian Day and Seasons

• Martian day 24.6 h
• equatorial tilt 24.0 degrees -- both close to
  Earth THEREFORE MARS HAS SEASONS TOO.
• Mainly red/orange surface with variable markings
• Shifting dunes change markings --- not canals and
  vegetation (as argued by Lowell)
• Polar caps variable parts are mostly CO2, not
  H2O Latest measurements indicate most of both
  permanent (residual) caps is water ice.
  Atmosphere gains and loses carbon dioxide from
  the caps.

6
Views of Mars
Pic-du-Midi, Hubble Space Telescope, Viking
pictures
7
MARTIAN TOPOGRAPHY

• S. Hemisphere higher by several km heavily
  cratered
• N. Hemisphere mostly volcanic plains
  (maria) probably only 3 billion years old,
  vs. 4 billion years for S
• Tharsis bulge --- near equator and 10 km
  higher. 4 big volcanoes on Tharsis and 100s of
  good sized ones
• N hemisphere and Tharsis indicate early (or
  failed) tectonics

8
N/S hemispheres Martian map
9
Olympus Mons Volcanic King

• 700 km diameter 25 km high 80 km wide caldera
  -- way bigger than any on earth. WHY?
• Lower gravity allows greater height and lack of
  tectonic motion allows huge build-up (vs Hawaii).

10
Polar Caps

• S cap residual about 350 km diameter
• N cap residual about 1000 km across dustier and
  warmer.
• Variable CO2 residual H2O

11
Marss Interior Structure

• CRUST some 100 km thick
• MANTLE some 2050 km thick -- not plastic now
• CORE some 1250 km in radius --- FeS
• No bulk MAGNETIC FIELD ? no liquid and/or no pure
  Fe/Ni (since it does spin fast)
• Percentage-wise less metal than other
  terrestrial planets
• Mars is small, and it cooled off too fast to
  establish plate tectonics

12
THE BIGGEST CANYONS

• Mariners 4 and 7, Viking, Global Surveyor, and
• Pathfinder showed Mars has large Canyons due to
  TECTONIC FRACTURES
• Valles Marineris, near Tharsis bulge (vs Grand
  Canyon)
• 2 billion yrs old 4 km deep 4000 km long 120
  km wide

13
Real Canyons ? (Was) Running Water

• RUNOFF CHANNELS, that merge like river valleys
  (Mars vs Red River) about 400 km long by 5 km
  wide

14
Outflow Channels Huge Flood Relics
15
FLUIDIZED EJECTA near IMPACT CRATERS

• Lunar crater (Copernicus) shows dry ejecta
• Martian crater (Yuty) shows liquid/mud flows
• Martian craters erode much faster than lunar
  ones windblown dust meteorites

16
Liquid Water on Mars NOW?

• Recent images MAY indicate CURRENT SEEPAGE OF
  WATER from PERMAFROST

17
MARS HAS PUNY MOONS

• Discoverd by Asaph Hall in 1877, these are
  probably captured asteroids since densities are
  low (2 g/cm3 ).
• Phobos (fear) 28 x 20 x 8 km a 9378 km P
  7h 39m ? backwards orbit
• Deimos (panic) 16 x 10 x 6 km a 23,459 km
  P 30h 18m ? slow

18
Spacecraft on Mars

• Vikings in 1976 Pathfinder/Sojourner in 1997
  Spirit Opportunity in 2004
• Red color from Fe2O3 --- rust
• Plains covered with boulders and rocks. Some
  sharp, some smooth and eroded
• Pathfinder site rocks deposited by old flood
• Spirit and Opportunity have drilled into rocks
  and gone into craters chemistry demands water
  was present.

19
Viking 1 2 Pathfinder Surface Photos
20
Spirit Opportunity Views Lion King
panorama, crater wall cliff, drilling site
hematite crystals
21
LIFE on MARS?

• The VIKING LANDERS, in 1976 conducted the only
  detailed studies so far
• Photos showed nothing moving.
• Gas-chromatograph/mass-spectrometer showed no
  organic compounds.
• Gas-exchange and pyrolytic release experiments
  search for metabolism and gave positive results
  (O2 and C, respectively),
• but sterilized samples also gave off gases
• Both anomalous results are probably due to UV
  irradiated soil and water yielding hydrogen
  peroxide (H2O2).
• Labeled release experiment gave off radioactive
  gas while sterilized soil didn't.
• Probably due to C2O3 -- carbon suboxide.

22
Meteoritic Evidence for Fossil Life?

• Meteorite ALH84001, found in Antarctica, came
  from Mars it provided controversial evidence for
  bacterial fossils Rock structures similar to
  bacterial products PAHs Magnetite found where
  carbonate dissolved Rod-like structures --- but
  very (too?) small!
• Most investigators think that ALL this "EVIDENCE"
  of life on Mars is NOT CONCLUSIVE and could be
  explained by INORGANIC CHEMISTRY. WE NEED TO LOOK
  FURTHER!