Is There Other Life in the Universe?

So far no other life has been found outside the Earth, but there is reason to believe it may exist on Mars or in one of the moons of Jupiter or Saturn. The Jovian moon Europa is considered a prime candidate for life outside the Earth because of its vast subsurface ocean. Generally, the strategy in the search for life is "follow the water".

The National Aeronautics and Space Administration and the European Space Agency are planning a mission to explore what are now being called "habitable worlds", a term that is being used more frequently by NASA to describe Europa, Ganymede, and Callisto. The reason is clear: The general rule is that where there is water, there is a higher probability of life.

The mission, called the Outer Planet Flagship Mission, has two components: A Jupiter Europa Orbiter (JEO) led by NASA, and a Jupiter Ganymede Orbiter (JGO) led by ESA. The proposed schedule begins with concurrent launches in 2020, followed by exploration of the Jovian moon Ganymede in 2025 through 2029 and exploration of Europa in 2026 through 2029. On the way, JEO would explore the Jovian moon Io from 2025 through 2027. The Jovian moon Callisto would be explored during the years 2026 through 2028.

Ganymede and Callisto are also believed to have subsurface oceans. Planetary scientists and physicists base the conclusions about subsurface oceans on observation of the moons as they rotate the parent planet.

David Southwood, ESA Director of Science and Robotic Exploration is excited about the mission: "What I am especially sure of is that the cooperation across the Atlantic that we have had so far and we see in the future, between America and Europe, NASA and ESA, and in our respective science communities is absolutely right. Let's get to work."

The missions are part of a larger pursuit that has fascinated scientists for hundreds of years: Is there other life in the universe? Through the JEO mission, scientists hope to find out whether Europa harbors life, or at least establish whether it is capable of harboring it. The theory is that life may exist in the subsurface ocean. Some of the scientific objectives of the Europa mission are to gather detailed information on the subsurface oceans, the ice shells and any subsurface water.

In addition to Europa, Callisto, and Ganymede, Enceladus - a moon of Saturn - is known to have water. Water plumes have been observed spewing from Enceladus.