Mars

Mars is next to the planet Earth. Mars is bigger than Mercury but smaller than Venus and Earth. It has two moons that are too small to influence anything ( Earth's Moon influences tides). Mars has volcanoes, a cayon and polar caps. There is evidence of dried-up riverbeds. Astronomers believe that there was an ocean on the Northern atmophere. That is why there is less craters on that part of the planet. There have been soil samples taken, several landings and many photos of the planet have been taken. But humans have not yet visited this planet, it is below freezing, air pressure is very low, not enough oxygen to breath and no atmosphere to protect you from the harsh ultraviolet radiation from the Sun.

Earth

Earth, well we know there is life there! But there are organisms on earth that could help us understand the possibilities for life else where.

By Bjorn Carey

Extremophilic microbes are a wild bunch. They can be found thriving in some of the most hostile environments imaginable — swimming in near-boiling water, eating rocks, lounging in subzero temperatures and hanging out where radiation levels rival nuclear reactors.
They’re tougher than duct tape, boldly going where humans dare not and cannot.
Extremophiles are also a multimillion-dollar-a-year business — some of them are employed to eat oil and help clean up spills. Others have important applications in medical research. But for many scientists, these hardy microbes are interesting because they suggest the potential for life on other planets.

Copied from: http://www.msnbc.msn.com/id/6928753/

If such a organisms can live in extreme environments, then maybe there are organisms living in extreme environments else where.