Geol 1420 Chapter 10.2

Water on Mars

• Existence of Running Water
    - Question: Was there running water on Mars?
      - Evidence: Runoff channels on Mars resemble those on Earth.
      - Comparison: Left image shows Mars; Right image shows Louisiana.
  
  

• Historical Presence of Open Water
    - Open water bodies (including rivers and lakes) once existed on Mars.
    - A catastrophic flood event occurred approximately 3 billion years ago.   

• Martian River Delta
    - The presence of an ancient river delta may indicate past water flow on Mars.   

• Oceanic Evidence
    - Much of Mars's northern hemisphere may have once been covered by ocean.   

• Impact Craters and Surface Age
    - Analysis of impact craters less than 5 km across shows they have mostly eroded away.
      - This erosion helps in estimating the surface age of Mars.
      - Some craters were formed when the surface was liquid, indicating liquid water presence in history.   

• Recent Observations of Gullies
    - Recently observed gullies suggest the presence of liquid water, though interpretations remain uncertain.
    - A pair of images indicate that gully formation is ongoing, hinting at current water activity.   

• Current State of Water on Mars
    - Some water may currently exist as permafrost under the polar ice caps.
    - Images of Polar Caps:
      - Left image: Southern polar cap, mainly composed of carbon dioxide.
      - Right image: Northern polar cap, predominantly made of water.
      - Both images captured during local summer.

Views of Mars

• Viking Landers
    - Both Viking landers landed in the low-latitude northern plains.
    - Appearance: Rocky surface, characterized by a red color due to iron content.   

• Opportunity Lander
    - Specific images of Opportunity Lander contributing to Martian data collection.   

• Phoenix Lander
    - The Phoenix lander found ice beneath the surface of Mars, showing potential for past water.   

• Curiosity Rover
    - Launched in 2012 and actively searching for evidence of water by examining carbonate rocks.

Discovery: Life on Mars?

• Viking Lander Missions
    - Conducted searches for signs of living organisms.
    - No conclusive evidence was found.   

• Martian Meteorites
    - Two meteorites discovered in Antarctica show possible signs of microbial life.
    - The evidence remains disputed among scientists.

The Martian Atmosphere

• Composition
    - The atmosphere of Mars is primarily carbon dioxide and is very thin.
    - Insufficient atmospheric density: Too thin to retain significant heat, leading to sharp temperature drops at night.

• Fog Formation
    - Fog can form in low-lying areas under certain conditions, particularly when sunlight strikes these areas.   

• Runaway Greenhouse Effect
    - Mars may have experienced a runaway greenhouse effect, opposite to that of Venus.
      - As water ice froze, Mars's surface became increasingly reflective, thinning the atmosphere further, which trapped more water and eventually froze carbon dioxide.
  
  

• Historical Atmospheric Conditions
    - There is speculation that Mars may have had a thicker atmosphere and liquid water in its past, both of which have since disappeared.

Martian Internal Structure

• NASA's InSight Mission
    - Conducted seismic studies between 2018 and 2022.
  
  

• Crust and Mantle Composition
    - Crust thickness ranges between 20-40 km.
    - Mantle thickness is between 400-500 km.
    - Core radius estimated at approximately 1830 km.
    - Findings suggest mantle heterogeneity and the presence of a solid inner core.

The Moons of Mars

• Mars's Moons
    - Mars has two small moons:
      - Phobos: Dimensions of 28 × 20 km.
      - Deimos: Dimensions of 16 × 10 km.
    - Origins:
      - Deimos: Likely captured from the asteroid belt.
      - Phobos: May have formed from material ejected due to a meteor strike on Mars.   

• Mars's Orbital Characteristics
    - Mars's orbit has higher eccentricity compared to Earth.
    - Rotation period: Approximately 24.6 hours; axial tilt is similar to Earth’s.
    - Average temperature is about 50 K lower than Earth's, but seasonal patterns are comparable.

Summary of Chapter 10

• Geological Diversity
    - Significant differences between northern and southern hemispheres.
      - Southern hemisphere: Higher elevation, heavily cratered.
      - Northern hemisphere: Lower elevation, relatively flat.   

• Major Geological Features
    - Features include the Tharsis bulge, Olympus Mons, and Valles Marineris.
    - Crater ejecta indicates the presence of a permafrost layer under the surface, which could easily become liquid.   

• Presence of Moons
    - Mars is accompanied by two small moons, Phobos and Deimos.

• Data Collection from Martian Landers
    - Mars landers have contributed substantial amounts of data, enhancing our understanding of the planet.