When a moon or planet is between two larger bodies, such as
a star and a large planet, or even two very large moons, the
large bodies pull at the little one with their gravity. The smaller
body can't escape, and cannot fall toward either of the larger
bodies, so the pulling puts stresses on the smaller body.
If a moon is near a planet, the gravity of the planet and
the sun could pull the moon this way and that. Sometimes the
gravity pulls on the moon in opposite directions. At other times,
the pulling might be from similar directions. The gravitational
pulling causes stresses which cause friction in the rocks. The
rocks, of course, move only a little, but that is enough to generate
heat. The heat may cause lava to come out, or even water, if
the planet is covered with ice. Scientists think that they have
seen evidence of ice volcanoes on Titan, a moon in our solar
little animated picture shows an exaggerated view of the pulling
and squeezing that could result. Of course, the distortion would
be much, much less. However, you can see that the crust of the
planet would experience some distortion -- and lots of earth
If the moon or planet were covered by a frozen ocean, ice
near hot rocks might melt deep under the surface, providing liquid.
If living organisms evolved here, they would live in darkness,
getting warmth and chemicals from geothermal
processes. Some organisms
that live on geothermal energy have been found near volcanic
vents deep in the oceans of the earth.
Scientists have even
found bacterial living
in rocks underground
on our planet!
Who knows what life forms may exist on other worlds?
2003. Elizabeth Anne Viau.
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