Earth and Mars Stats

Distance from the sun (Golidlocks/habitable zone)

Length of year (revolution)

Axial tilt (angle of inclination)

Moon/s (natural satellite)

Length of day (rotation)

Axial tilt (angle of inclination)

Size (diameter and/or mass)

Gravity (How much do you weigh on Mars?)


Polar caps (more info on Mars Polar caps)

Atmospheric composition

Average surface temperature

Atmospheric pressure

Include an explanation of each feature if you're unsure what they mean, eg. the length of a year is determined by the time it takes to make one revolution of the Sun. Include diagrams if you wish. Paste the foldable into your science notebook, we will refer to it again.

Can liquid water exist on Mars?

On Earth, water normally freezes at 00 C, but atmospheric pressure also effects the freezing (and boiling) temperature of water. A phase is another term for solid, liquid or gas. We can use a phase diagram to see what happens to water at different temperatures and atmospheric pressure.

  • At 1 atmospheric pressure (sea-level on Earth) water boils at 1000 C (becomes a gas - water vapour); water freezes at 00C (becomes a solid - ice).

  • Read the diagram at 1 atmospheric pressure to see the boiling and freezing point of water.

  • Above the critical point liquid and gas phases do not exist,

  • At the triple point all three phases can coexist.

  • Mars' average atmospheric pressure is less than 1% (0.006) of Earth's.

Here is a phase diagram for carbon dioxide. Note that at 1 atmosphere (on Earth) carbon dioxide can only exist as a solid or gas. Liquid CO2 can only exist at higher pressures and colder temperatures.

TASK 2: Use the phase diagrams to answer the following question: Can liquid water exist on Mars? Explain your answer by referring to the diagram (watch the video if you've forgotten how to read a phase diagram).

Next we'll compare some surface features of Earth and Mars:

  • Impact craters (created by meteorites)

  • Volcanoes (magma erupting from an opening in the Earth)