Earth, our beloved home planet, is unique in the solar system. Simply by viewing a montage of planets, one can easily see that Earth has special properties that set it apart from other bodies. As we go about our everyday lives, we forget (or are unaware to begin with) that we are on an orbiting planetary body that is surrounded by a hostile environment. Earth's atmosphere and magnetic field protect us from violent phenomena such as cosmic rays, solar wind, temperature extremes, a near vacuum, small meteorite bombardment, etc. Without this protective environment, life as we know it would not be possible.

Image Courtesy of the Jet Propulsion Lab (Images not to scale)

One of the reasons our planet is so special is the presence of water in all three physical states: liquid, solid, and gas (vapor). Water is essential for many processes on Earth. Most notably, liquid water is a necessary ingredient for life. There are only two other places in the solar system where large bodies of water might exist in liquid form: buried in the subsurface of Mars, and underneath an icy layer on Jupiter's moon Europa. Indeed, these two locations are prime targets in which Astrobiologists (scientists who study possibilities of life in the universe) look for organisms beyond our home. To learn more about why Earth is an island in the vastness of our solar system, read on for more information about our planetary neighbors and their different types of environments.