Watched a show recently that indicated that it's likely that Mars encountered a similar event to the presumed Earth/Moon collision, but Mars didn't fare so well. Mars was left lacking a singular large moon to protect it and a fairly unstable wobble of its rotation. It apparently moves between a global ice age to a far more temperate climate around every 120K years. Coupled with a lack of a magnetic field to protect its atmosphere, it's been stripped of most of what we think of life harboring facilities such as atmosphere and prevailing liquid water. This is mostly a recap of what I saw a Science Channel show, so don't judge me too hard - just trying to recap. Definitely not my area of expertise.