Planetary Science: Mars, Jupiter, and Outer Moons

Posted on May 29, 2025 in Geology

Mars: Atmosphere, Water, and Polar Caps

  1. Current Martian Atmosphere and Past Evidence

    Describe the current atmosphere on Mars. What evidence suggests that it must have been different in the past?

    1. The atmosphere is thin, 0.7% of Earth’s, and is composed of 95% CO2.

  2. Evidence of Water on Mars

    What evidence do we have that there was running (liquid) water on Mars in the past? What evidence is there for water coming out of the ground even today?

    1. The ice caps and the subsurface of Mars have significant amounts of water.
    2. In the past, Mars was more geologically active compared to today.
      1. Volcanic activity added water, CO2, and nitrogen to the atmosphere, making it warmer and wetter.

  3. Mars Odyssey’s Water Detection Method

    How was the Mars Odyssey spacecraft able to detect water on Mars without landing on it?

    1. It detected water by using the reflection of neutrons.

  4. Composition of Martian Clouds

    What is the composition of clouds on Mars?

    1. Clouds are composed of water and CO2 in the form of both vapor and ice crystals.

  5. Composition of Martian Polar Caps

    What is the composition of the polar caps on Mars?

    1. Polar caps consist of water ice and dry ice (CO2).
    2. They comprise a seasonal cap (much like snow cover) and a permanent cap (similar to Earth’s arctic regions).

Jupiter: Interior and Heat Sources

  1. Physical State of Hydrogen in Jupiter’s Interior

    At the pressures in Jupiter’s interior, describe the physical state of the hydrogen found there.

    1. The hydrogen found in Jupiter’s interior is crushed into a “metallic” state.

  2. Primary Source of Jupiter’s Internal Heat

    What is the primary source of Jupiter’s internal heat?

    1. It is the leftover heat from Jupiter’s formation.
    2. This indicates a large heat reservoir exists, which will take billions of years to cool down.

Outer Planet Moons: Composition and Geology

  1. Composition of Outer Planet Moons vs. Earth’s Moon

    What are the moons of the outer planets made of, and how is their composition different from that of our Moon?

    1. The moons of the outer planets are primarily made of ice.
    2. They are composed of a mixture of silicate rocks and ices, exhibiting approximately the same density.

  2. Geological Comparison: Callisto, Ganymede, and Titan

    Compare the geology of Callisto, Ganymede, and Titan.

    1. Callisto Geology

      1. Surface appears dark.
      2. Similar to Ganymede in overall structure, but with approximately 10 times the number of visible craters and less surface relief.
      3. Crater counts suggest an old surface with little geological activity.
      4. Appears to be a largely undifferentiated ball of rock and ice.

    2. Ganymede Geology

      1. The largest moon in the solar system.
      2. Has a lower mean density compared to Io or Europa.
        1. This implies a greater concentration of icy material and less rocky mass.
      3. Composed equally of silicate rock and ice, with its surface composed of water ice.
      4. Exhibits more hills than Io or Europa, indicating more topographic relief.
      5. Shows evidence for early geological activity (ice plate tectonics), but is now a geologically dead world.
        1. Like Europa, a substantial subsurface liquid ocean may exist, though more deeply buried.

    3. Titan Geology

      1. The second largest moon.
      2. The only moon with a substantial atmosphere.
      3. Lakes and small seas of liquid ethane and methane exist on its surface.
      4. An active weather cycle occurs, where methane replaces water.
      5. Bulk composition is half water ice and half other rocky material, based on mean density and observed surface properties.

  3. Europa’s Liquid Ocean and Extraterrestrial Life

    What is the evidence for a liquid water ocean on Europa, and why is this interesting to scientists searching for extraterrestrial life?

    1. It is highly reflective.
    2. Some evidence for water geysers was spotted by Hubble in 2012, but they don’t occur frequently; their exact nature is under debate.
    3. The Galileo probe found evidence that it may have a subsurface ocean made of water.
    4. It is interesting to scientists because they are designing a Europa mission to characterize its liquid ocean, which could potentially harbor life.

  4. Energy Source for Io’s Volcanoes

    Explain the energy source that powers the volcanoes of Io.

    1. The active geology of Io is driven by tidal stresses, caused by Jupiter and Europa as Io swings in its orbit around Jupiter.
    2. These tidal stresses flex and heat Io’s interior, causing much of it to be molten.

  5. Comparison of Titan’s and Earth’s Atmospheres

    Compare the properties of Titan’s atmosphere with those of Earth’s atmosphere.

    1. Atmospheric pressure at the surface is 1.6 times Earth’s; the atmosphere extends to 200 km.
    2. Titan’s atmosphere is composed of 90% nitrogen, 10% argon, with traces of methane, carbon dioxide, and ethane.