History of Mars

Ge151: Spring 2011

Planetary Architecture and Surface Units

• Comparison of Earth, Venus, Mercury, Moon, Mars
  

1. Architecture

• Topographic map
• N/S Hemispherical Difference
• Gravity/Topography relationships
• Crater/size frequency

2. Basins

• USGS maps
• papers
• compression
• new MOLA interpretations
• Hellas age plot

3. General Stratigraphic Categories

• USGS maps
• Crater/age relationships
• Stratigraphic series
• Epochs, crater-density ranges and absolute age ranges

4. Noachian

5. Transition to Fluvial Features

6. Old Layered Deposits

• Layered unit in Gale Crater mounds
  Oblique view of layers in crater
  Oblique view of Gale Crater Mound

Grand Canyon and Gale geologic sections
Locations of layer outcrops

The Middle Years - Introduction

During the Noachian, large amounts of "lithospheric" water seems to have been incorporated into the Martian crust, presumably in conjunction with the Late heavy Bombarment. During the Hesperian large amounts of such "lithospheric" water was released onto the surface, much of which probably ended up in the North Polar basin. Additional amounts may have flowed underground because of the large S-N global topographic gradient.

Water-Related Features

• Outflow Channels

Highland Example

• Hellas Area
• Geographic nomenclature
• Topographic map
• Geologic map
• Crater Terby
• Northwest basin rim of Hellas
• Terra Tyrrhena

Chryse Basin Drainage

• Ivanov paper
  • Channel sequence
  • Crater ages
  • Topographic distributions
  • Geologic map
  • MOLA altimetry
  • Outflow channels
• Moore paper
  • Relative ages of flooding events
  • Age map of outflow channels
  • Ravi Vallis channel
• Chryse Basin Geology
• Geologic Sketch Maps

Volcanism

• Location map of Mars
• Terrestrial examples: inflated pahoehoe flow surface morphology
• More terrestrial pahoehoe
• Still more terrestrial pahoehoe
• Terrestrial example: Laki flow field, Iceland
• More of Laki flow field
• Formation of rafted plains
• Rafted plains in Viking and MOC images
• Flow lobe terminus, Viking and MOC images
• Amazonis Planitia, Viking and MOC images

Water History

• Erosion
•  Noachian  Early Hesperian  Late Hesperian

Issues

• Ice-covered Bodies of water?
• Shorelines? Compatible with Ice-covered?
• Where did the water go?

Introduction To The Amazonian

• The Amazonian is the most recent geologic time division in Mars' history.
• Volcanic flows in the Tharsis region.
• Extensive aeolian activity.
• Cap - 'layered deposit' systems in the North and South.
• A large seasonal cap cycles about 1/3 of the atmosphere through a solid vapor transition.

Layered Deposits North and South

General features



• First discovered by Mariner 9
• Commonly though to be composed primarily of ice with varying concentrations of dust giving a layered appearance.
• The polar layered deposits may contain a recoverable stratigraphic history.
• The layered deposits in the south appear much older from crater counts, the northern deposits contain no craters
• Both the north and south caps appear extremely young




Local features



• Mass movements may provide an additional means of scarp retreat (MOLA profile).
• The layered terrain may also experience large scale gravity faulting due to oversteepening of scarps.
• Exposed layers darken as the season wears on.
• Layers appear to be rhythmically bedded in some locations

North Polar Residual Cap

• Water Ice cap overlain by seasonal CO₂ only. Significant source of water vapor for the Martian Atmosphere.
• Glacial activity postulated at the rate of a few cm/year.
• The north and south polar cap retreats reproducibly to the same shape each year
• The surface of the north residual cap has been described by 'Cottage Cheese' or a 'Sponge'.
• The north polar region sits inside a large basin.
• Fishbaugh & Head paper
  • Stratigraphic Column
  • More stratigraphic column
  • Polygons
  • Altimetric Profiles
  • Chasma Boreale
  • Polar Cap Outliers
  • Cross sections
  • More cross sections
  • Topographic profiles
  • Geologic Map
  • Tanaka and Scott geologic map
  • Topographic Map
  • Geologic map superposed on topographic data

South Polar Residual Cap

• The south polar residual cap is smaller than the north's and never rises above the CO₂ sublimation temperature (148 k).
• Originally thought that the cap was solid CO₂ ice but now its believed (due to reologic modeling) that its water ice with some thin veneer of CO₂
• The surface of the residual cap is littered with depressions, dubbed 'Swiss Cheese' - Closeup.
• These Swiss cheese depressions are evolving fast (http://www.msss.com/mars_images/moc/CO2_Science_rel/)
• The cap is incised by several dark lanes which contain layers - Closeup.
• The south polar region sits on a topographic high as part of the southern highlands

Obliquity and Eccentricity Variations

• Eccentricity Controls Magnitude of Perihelian Heating and Probably Magnitude of Global Wind Storms and Sediment Transport
• Obliquity Controls Average Annual Polar CO₂ Temperature and Therefore Surface Pressure.
• Classic Milankovitch vs Chaotic Theory

Current Surface Processes

• Discovery of the Gullies
• Aeolian Modification Ubiquitous
• Volcanism = probably dead
• Glacial activity ?

Issues

• How big is the South Polar CO₂ reservoir ?
• Is glacial flow operating ?
• What is the absolute age of the Amazonian/Hesperian boundary?
• Life on Mars?

References

Tanaka, K.L. and G. J. Leonard 1995. "Geology and landscape evolution of the Hellas region of Mars". JGR 100 no. E3, pp 5407-5432.

Moore, J.M. et. al. 1994. "The circum-Chryse region as a possible example of a hydrologic cycle on Mars: Geologic observations and theoretical evaluation". JGR 100 no. E3, pp 5433-5447.

Ivanov, M. A. and J. W. Head 2001. "Chryse Planitia, Mars: Topographic configuration, outflow channel continuity and sequence, and tests for hypothesized ancient bodies of water using Mars Orbiter Laser Altimeter (MOLA) data". JGR 106 no. E2, pp 3275-3295.

- Byrne and Murray -

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