Water is Life

 I asked a class of fifth graders what we would look for first if we were searching for life in the solar system. A couple of the kids squealed, "oxygen!". "Nope",  I said. Oxygen on Earth is a by-product of photosynthesis. It is essential for animal life but not for plant or bacterial life.  "What is essential for bacteria?" at this question, I refer to my 46 meter geologic timeline of planet Earth. We scan the timeline for the first signs of life found in the geologic record, about eight meters or 800,000,000 years in, we see the evidence of chemotropic bacteria in Earth's vast oceans. I remind the kids that ALL life on Earth relies on one thing. Water. There is no life without water.  
And this is why scientists and laypersons alike get excited about what the NASA / JPL missions to Saturn and Jupiter have revealed.....water, oceans, geothermal heat and the possibility of life within our solar system.

Titan has an atmosphere of nitrogen and methane (a hydrocarbon that once filled Earth's atmosphere), a frozen crust of methane and water and a subsurface ocean of liquid water.

Titan and Saturn

Enceladus



Enceladus is Saturn's 6th largest moon. It has a global ocean warmed by the internal heat of the moon itself. The gravitational pull of Saturn on it's moons is probably responsible for the heat generated in the center of the moon. These tidal forces are also responsible for the subsurface oceans in the Jupiter system.


    This is Europa. I saw the movie 2010, The Year We Make Contact, when I was in High School and it stirred my sense of wonder. Europa was the moon that would harbor and support the evolution of life in the film. 
As our scientific knowledge has grown, we have learned that Europa, Ganymede and Callisto, the outermost of the Galilean moons, all have subsurface oceans of liquid water and all have the geothermal energy from Jupiter's tidal forces to stir our imaginations into believing that life is actually a possibility.



Water on Europa vs. water on Earth

Europa has more water than all of the water on Earth.

A source of geothermal energy on Europa 

Europa

Ganymede



Callisto

The following images are webs of life that are supported not by sunlight but by the heat from deep oceanic geothermal vents. The bacteria supported by the chemicals from undersea volcanoes are chemotrophs. They are able to create energy from chemicals instead of sunlight.  This is the kind of life we would expect to find on the distant watery worlds of the gas giant moons. 


These large tube worms are also part of the deep oceanic chemotrophic food web. 


Considering the five major mass extinctions Earth has endured, it seems clear that with water, there will be life. Water appears to be far more abundant than previously thought. Life may also follow that pattern.


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