The polar regions of Mars have a surface layer of Carbon Dioxide (CO2), but the bulk of frozen material is:
Permanently frozen water ice
According to the book, what evidence and features may indicate the Mars once had liquid water? (Check all that apply)
What appears to be "river channels" are on the surface, indicating that water must have flowed.
Presence of "islands" around rims of craters, indicating that water likely flowed in the past.
Possible dried river deltas with fans of sediment about 13 kilometers wide.
Fossilized sea life (bacteria and algae) have been found.
A "Crater Lake" that seems to have terraces that resemble old beaches.
In the past, Mars had a , which allowed for volcanism to take place on the planet. When , they in the atmosphere, and the amount of CO2, a well-known greenhouse gas, making the atmosphere . The greenhouse effect, in addition to a atmospheric pressure allowed for the surface temperature to be , and for to be present on the surface.
Mars' atmosphere is made of mostly Carbon Dioxide (CO2), a well-known greenhouse gas, in fact its atmosphere closely mimics Venus' atmosphere. Greenhouse gasses trap heat in a planet's atmosphere, and increases the temperature. If this is true, why doesn't Mars' have a similar temperature to Venus?
Mars' atmosphere has a very low density, so the greenhouse effect is much weaker.
Mars is so far from the Sun that it doesn't receive enough heat to experience the greenhouse effect.
Mars' strong seasonal winds mix up the atmosphere, so any heat it traps becomes lost again.
Mars' weak magnetic field causes the atmosphere to be lost constantly, so it cannot have a greenhouse effect.
Why does Mars not have liquid water on its surface?
The low atmospheric pressure causes the water to "boil off"
The high atmospheric pressure causes the water to "boil off"
The cold temperatures freeze all the water, though this ice covers large portions of the surface.
The cold temperature causes the water to become gaseous.
Eventually Phobos (one of Mars' moons) will spiral in and crash into Mars due to tidal drag.
Deimos and Phobos, Mars' moons, are thought to be captured asteroids.