Tour of the Solar System: The Planet Earth

The Big Blue Marble of the solar system is also the third big rock from the Sun. It is our Home.  Earth is the only place in our solar system where life has been confirmed.  It is also the only place in our solar system where biotic life plays an active role on modifying the planet's atmosphere and surface. Whether it is humans moving land, releasing gasses from industry, or whether it is the smallest microbe, releasing oxygen, methane, carbon dioxide, or some other gas into the atmosphere.  We live on a truly unique planet.  At least as far as our own solar system is concerned.

Now there is big debate as to whether life exists outside of our terrestrial confines, either somewhere else in our solar system, or out in the vast Universe. It almost seems as if the new goal for the space race between certain countries on our planet is to see which country will be the first to confirm the existence of life outside of our planet. Missions are headed to Mars to look for more early signs of life, some are planned for Venus as well.

NASA has already uncovered faint possibilities that life may have tried to get started on Mars early in its development.  But the mostly likely places for extraterrestrial life in our own solar system do not lie on planets at all, but on some of their moons.  Specifically, Saturn's moon Enceladus and Jupiter's moon Europa.  Titan and Io are also candidates.  These moons seem to have water and are either not too hot or cold. Titan seems to have a replenishing source of Methane, a by product of biologic processes.  But, that is a post for another day.

Even if the building blocks of life exist on just one other place beside Earth in our own solar system, think of the possibilities.  I once heard Stephen Hawking say on a documentary on television  somewhere that our universe is so large and vast, and contains so many stars and galaxies, that even if one billionth of a billion stars had the still remote chance of sustainable life, then the number of planets with sentient beings like humans could still number in the billions throughout our universe.  He even supposed that by pure chance, there could be civilization that are modeled after our own Star Trek and Star Wars science fiction series.  They may even exist right now somewhere in our universe. Now that is mind boggling!  Imagine monkeys writing Shakespheare anyone?