Alan Stahler: Food for (very) young life
April 19, 2017
Electrons! I must have electrons! My belly growls for electrons!
Electrons: Tiny particles, smaller than atoms. Scrape some gazillions of electrons off their atoms — say, by stroking a cat on a dry winter's day – and they make sparks as they zap back to their atoms.
I must have electrons to live. But I am no piece of electronic machinery, no monster born in a lab. You, dear reader, need electrons as much as I, crave them, hunger for them.
Water on top of a hill feels where gravity "wants" it to be, and flows downward. Place a waterwheel in the flow, and the water spins the wheel, shares the energy of its fall with the wheel, shares its energy with us when we connect the wheel to an electrical generator.
Like water flowing downward, electrons jump to where they're wanted. Oxygen really wants electrons, and they flow toward it eagerly.
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Channeling the energy of sunlight, green plants strip electrons off molecules of water, and paste those electrons, along with some hydrogen, onto molecules of carbon dioxide. The process makes food – electron-rich food.
We eat that food, pull some of the electrons off, and offer those electrons to oxygen. As electrons flow toward and onto the oxygen, we harvest energy to keep ourselves alive.
Life needs water, and it needs electrons — it needs food. Before life invented photosynthesis — before life could harness sunlight —living things depended on the non-living world to make their food — to make substances rich in electrons.
In the non-living world, interesting reactions can take place where water and rock and heat come together. Millions of years ago, where the foothills now rise – our home-turf – marked where North America met the sea. Seawater-infused rock was squeezed and cooked into the green mineral, serpentine. The rock-reaction released hydrogen gas. Hydrogen is rich in electrons; microbes today, living underground or underwater, still enjoy eating hydrogen.
Earth inhabits a Goldilocks region of the solar system — not so near the sun that all our water would boil away, not so far that all our water would freeze. Until recently, it was thought that only Earth could harbor liquid water, and, therefore, life.
Bend a paperclip back-and-forth, quickly, half-a-dozen times, then touch the clip to your lip. Internal friction — atoms rubbing against one another — makes the clip hot.
Saturn orbits the sun a billion miles out, way too far for water to remain liquid on the surface of its moons. But the moons of Saturn pull on one another, and Saturn pulls on them all. As gravitational tugs flex the moons, internal friction generates heat. Saturn's moon Enceladus (en-SELL-uh-dus) has a surface of solid ice. But below the surface, the ice has melted, forming an ocean of liquid water.
The spacecraft Cassini has been studying Saturn for a decade, all the while playing it safe, keeping its distance from the moons. But Cassini will end its mission, plunging into Saturn this fall. Now it takes risks, swooping down close to the moons.
Cracks in Enceladus' icy surface allow seawater from its inner ocean to spurt out into space as geysers. Cassini has flown through those geysers, and found, mixed with the water, hydrogen — super-nutritious hydrogen.
We don't know yet if life may be evolving in the Enceladusian ocean. But deep beneath its surface, reactions between warm rock and water seem to be creating electron-rich food that could keep such young life alive.
Al Stahler enjoys sharing nature with students of all ages. His science stories can be heard on radio station KVMR (89.5 FM), and he may be reached at email@example.com