Mars_Texbook_Part

10.4 The Geology of Mars

Learning Objectives

• Discuss the main missions that have explored Mars

• Explain findings from examination of Martian meteorites

• Describe various surface features of Mars

• Compare Martian volcanoes and canyons with Earth's

• Describe general surface conditions on Mars

Mars as a Celestial Body

• Mars is considered more interesting than Venus due to its hospitable conditions.

• Visible features such as surface characteristics and seasonal polar caps can be observed from Earth.

• Evidence suggests Mars once had liquid water and a hospitable environment.

Spacecraft Exploration of Mars

• Over 50 missions sent to Mars; about half successful.

• US Mariner 4: First spacecraft to pass Mars (1965), transmitting bleak images of craters.

• Mariner 9: First orbiter mapping the surface, revealing a variety of geological features.

  • Key findings included:

    • Volcanoes

    • Canyons

    • Polar cap layers

    • Channels indicating water flow.

• Viking Missions (1970s): Successful landers that searched for life and conducted extensive experiments.

• Pathfinder & Sojourner Rover: First wheeled rover on Mars in 1997, revealing geologic features in detail.

• Mars Global Surveyor (MGS): Provided high-resolution photography, found evidence of gullies cut by water.

• Mars Odyssey and ESA Mars Express: Conducted further research using advanced imaging.

• Curiosity Rover (2011): Investigated Gale crater complex geology, assessing habitability.

• InSight Lander (2018): Analyzed Martian geology with a suite of scientific instruments.

• Perseverance Rover (2020): Focused on ancient sedimentary rocks to find evidence of past life; included helicopter drone, Ingenuity.

Characteristics and Properties of Mars

• Global Properties:

  • Diameter: 6,790 km, surface area nearly equal to Earth’s land area.

  • Density: 3.9 g/cm³ indicates predominantly silicate composition with a small metallic core.

  • No global magnetic field but strong local magnetic areas indicate past presence.

• Elevation and Terrain:

  • Extensive mapping reveals a highland (southern) and lowland (northern) division.

  • Olympus Mons: Largest volcano, significantly taller than any on Earth.

  • Tharsis Bulge: Major volcanic region with four prominent volcanoes.

Martian Volcanoes

• Olympus Mons: 500 km in diameter and over 20 km high, with very few craters suggesting young geological activity.

Cracks and Canyons on Mars

• Valles Marineris: Extensive canyon system, not formed by water but by tectonic activity over 5,000 km long and 7 km deep.

• Primarily reshaped by wind and geological forces.

Martian Surface Views

• Early landers (Viking, Pathfinder) photographed similar rugged landscapes with angular rocks and dune-like deposits.

• Soil primarily made up of clays and iron oxides; volcanic origins noted.

Martian Weather

• Temperature extremes: From summer highs around -33°C to lows around -100°C.

• Seasonal frosts observed; dust storms capable of engulfing the planet.

Water and Life on Mars

Atmosphere Composition

• Average surface pressure: 0.007 bar, with 95% carbon dioxide.

• Thin atmosphere causes difficulty for liquid water to exist except under certain conditions (e.g., salty water).

Evidence of Water

• Polar Caps: Presence of CO2 and water ice; seasonal changes noted in composition and size.

• Features indicating ancient rivers, lakes, and potential for salty water flows seen in gullies.

Geological Features from Water

• Runoff channels and outflow channels demonstrate past water activity; suggests ancient climate differences.

• Recent evidence indicates possible current water flows in the form of recurring slope lineae.

Ancient Lakes and Glaciers

• Rovers reveal evidence of past water and glacial geology; layered sedimentary rocks seen indicating ancient aquatic environments.

Planetary Protection

• Important to avoid contamination when searching for life; trails from other celestial bodies must be avoided to preserve Martian integrity.

Conclusion

• The geological journey of Mars illustrates a once lively planet transitioning to dry, cold conditions. Understanding its evolution gives insights into planetary climate change and the potential for extraterrestrial life.