• Moreover, its constituents include gases that serve as an insulating blanket around the planet, keeping surface temperatures within the range necessary for the presence of liquid water and, hence, life as we know it.

• For example, the planet 's vegetation serves as a moderator of the increase in greenhouse gases.

• Although smaller objects hit the Earth more frequently, they have much less impact. Nevertheless, it is almost certain that another large comet or meteorite will at some time in the future strike the planet with potential consequences for the global climate and for life on Earth.