Mars has long captured our imaginations and remains a serious target for human exploration. With evidence of water once being plentiful on this planet, we take the maximum precautions when exploring this world. Many of the new protocols being developed are for the near future as we plan sample return missions.

Europa is a moon of Jupiter. Its frozen surface is believed to have an ocean of liquid water beneath it heated by tidal forces. Water and heat make it another candidate for a possible abode of life.

Titan, Saturn's largest moon has a smoggy nitrogen atmosphere. Its make-up is similar to our own atmosphere, but much colder. Cassini will drop a probe through the smog to give us more detailed information about curious moon.

Eros, was the first asteroid to have a spacecraft put in orbit around it. Given its size and location, it is not a likely candidate to have life on it. Even though the spacecraft was eventually landed on the surface, the precautions to sanitize the spacecraft were much less rigorous than they are for a destination like Mars.

Pluto is the most distant planet in the solar system and is more like a comet than a planet. Because it always lurks at the frozen edges of the solar system, it is not a likely candidate for life. Any future spacecraft that may explore this distant icy world, will still be assembled in clean rooms but will not have to go through the same level of sanitizing that Mars rovers are subject to.