Search for Life in Our Solar System

The search for life involves finding water.  Whether we are to find oxygen breathing life forms or carbon dioxide absorbing life forms like plants, water is a major requirement, and it must be in the liquid state.  So, we need only examine places where water is found. 

To find complex life, including intelligent life, would be a great surprise, for the few candidates where water exists are highly unlikely to harbor complex life forms.  Microbial life is another matter, and one or more of the candidates might well have microbial life. 

The largest moon in our solar system is Ganymede, and it is believed to have a vast ocean of water, possibly liquid water.  The problem here is the ocean, although possibly greater than all of the oceans of the Earth combined, is deep below the surface.  The problem this translates to is the food chain would be strained without sunlight to provide photosynthesis enough to sustain plants, and without plants could a real food chain exist?  I suppose one could argue that there is no requirement prohibiting complex life from being aquatic, but in the dark oceans beneath the surface it is highly unlikely anything past microbial life exists.

Ganymede is one of the four large moons of Jupiter that were discovered by Galileo.  Indeed, it is not the only Jovian moon to contain water. 

His subsurface ocean was recently in the news, and I found information on it on Wikipedia simply by looking at the article on Ganymede.  It is less often referenced than the next two candidates.

Europa is another of the Galilean moons of Jupiter, and it has long had the distinction of being a candidate for liquid water and life.  Europa has water ice on its surface.  I am specific here because other ices do exist, and can be found on moons in our solar system.

Deep below the surface could lie liquid water.  It has been speculated that gravity from other Jovian moons and the planet itself might have added enough internal energy to keep the water liquid below the surface.  In The Universe series, season 1, it is speculated that liquid water might exist under a mile or so of ice.

This is not likely to support higher forms of life, for the photosynthesis needed for plants to start the food chain is problematic at such depths.

This moon, with its surface ice, is hands off until proper exploration can be conducted.  In the past NASA sent a command to a satellite orbiting Jupiter to crash into the planet when the batteries reached a point where they might fail.  Under normal conditions the satellite would have been left in orbit and whatever data it transmitted accepted as a bonus, but a craft that could no longer be controlled might happen to crash on Europa, and in making contact with the moon could contaminate it.  If life were to be later found it might not be possible to determine if the life had been transported by the spacecraft.  Only when a sterile craft is launched will it be allowed to land and explore the subsurface water of Europa.

Enceladus is a moon of Saturn, and it was recently discovered by NASA to be ejecting plumes of water.  This was surprising since Enceladus is small, about three hundred miles in diameter.  These geysers send material upward and replenish a growing Saturnine ring, the E ring.  Of course some water ice falls back as snow and lands on the surface of the tiny moon.

Titan is Saturn’s largest moon, and the second largest moon in the solar system.  We have already considered Ganymede, the largest moon.  Titan has oceans or lakes that are made up of hydrocarbons, an important find when searching for life.  It also has a nitrogen rich atmosphere, and according The Universe season 1 it is the only moon in our solar system with an expended atmosphere.   Fortunately, there is not enough oxygen around.  Had it had adequate oxygen, a meteor or comet could easily have produced enough heat that a large explosion would have resulted.  Yet, even though there is no known water on Titan it is interesting in the search for life.

Pluto is another object with water or water ice in a large quantity below its surface.  NASA has just sent New Horizons past Pluto, and the discovery was somewhat surprising.  Of course water in the Kuiper Belt is plentiful, and Pluto makes incursions into the Kuiper Belt where much of its orbit lies.  Comets, Kuiper Belt objects, frequently have a large ice component.

Complex life is not likely in our solar system.  Most scientists would be elated with finding microbial life.  The focus for even that is narrow, and while another moon might reveal something of interest it is unlikely it would be much different than the moons discussed.

The focus here is that if there is complex life in the universe other than on the earth it is likely not to be in our solar system.  And even our nearest neighboring star if a craft left Earth would take generations to reach by our current abilities.  So, if there is complex life out there it is not likely we will be aware of it, for the distance to it would be too excessive.

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