Overview
In years past, the likelihood of life beyond the Earth was a topic usually set aside for science fiction writers. Today, scientists from a variety of fields are seriously considering the idea that "life" may have existed in other places in our own Solar System.
"The word "life" means any type of organism with the same (or closely similar)
physical and chemical make-up as living things on Earth; it has been assumed that
the range of conditions for active life that is found for Earthly creatures can be
applied outside the Earth. It is… possible that this is true, that any form of activity
that could be called "life" in a wider sense can occur only within the narrow range
of conditions found on the Earth and its neighboring planets. But it is equally
possible that the life forms that we find on Earth are just those that have evolved
and developed because they are suited to Earthly conditions; forms that have
remained primitive on Earth might, in the conditions on a different planet, have
evolved and developed." (Ovenden 75)
The recent study of life in the Universe, Astrobiology, has sparked new philosophical theories. One theory addressed by David Darling in The Maverick Science of Astrobiology projects "… the view that life may be able to adapt to all sorts of bizarre extraterrestrial regimes, perhaps including some that are on neighboring worlds in the Solar System. " (Darling 53) Over the past twenty years, some scientists have begun to look at the possibility that life may exist outside Earth. Life has been found flourishing in some unexpected places. Microscopic organisms have been found in deep sea volcanic vents and hot springs with almost boiling water. They have also been found in the frozen lakes of Antarctica and within rocks deep under the surface of the Earth. Life has proven to be surprisingly adaptable and robust. These life forms have been denoted as "extremophiles".
My students must understand that, as Earth was first formed, it was an extremely hostile place. Realizing that the large impact craters on the Moon, and other planets and moons in the Solar System, are proof of a time when the planets were common targets for large asteroids and comets. This is important because students tend to think that this was the way that the planets and moons were created not realizing that they were often subjected to collisions with sometimes very large interplanetary objects. The energy released by the largest of these impacts could have been capable of boiling the oceans into a thick steam atmosphere and sterilizing the surface of the Earth, keeping in mind that something like this is what probably caused the extinction of the dinosaurs. The scars of this atrocious time, which are still shown by the Moon, were erased long ago from the surface of the Earth by our ever-evolving planet. Fossil evidence in the form of simple organisms living 3.5 or even 3.8 billion years ago indicates that life apparently began on Earth almost immediately after the sterilizing impacts had ended. Students must be able to realize that this new life started as small microscopic life and eventually evolved into more complex forms of life. Collectively, the discoveries of life in extreme environments and the evident speedy source for life on Earth contend that life may be plentiful in the Universe and may exist or have existed elsewhere in our own Solar System.
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