Life in the Universe Introduction

The possibility of the existence of life on other planets has always fascinated humankind. As our technological capabilities grow, we are able to search for life outside Earth in earnest.

The existence of life forms in extreme Earth environments give us some clues to what life as we know it can tolerate. Scientists have found microorganisms in such hostile locations as ice-covered Antarctic lakes, deep subsurface rocks with temperatures above 160C, suboceanic hydrothermal vents, and even the interior of nuclear reactors. The discoveries of such organisms have expanded our knowledge of habitable ecosystems. If microbes can live in frozen Earth lakes, could they live in under the icy crust of Titan, which might cover an ocean of liquid water?

Liquid water is the one factor that all of the above mentioned habitats have in common. All currently identified life forms require water to live. It provides a surface for the exchange of nutrients and waste and a medium for catalytic molecules and the exchange of genetic material. Because of the necessity of water for life on Earth, the search for extraterrestrial life will most likely begin with the search for water on other planets.

To understand what planets may possess liquid water, we must know more about how Earth's water was accumulated and maintained. It may have been included in the original material from which Earth formed, or added later through the impact of asteroids or comets. And the question remains of how, over the past 4.5 billion years of changes in the Sun and its solar system, the Earth's water remained a liquid, not boiling off the surface of the planet. Understanding this would help narrow the search for habitable planets. Finally, knowledge of what structural fossils or chemical traces may signify extinct life would help us identify places in our own solar system and beyond where life once may have existed.

Teaching Goals:

Discipline Lead

John D. Rummel, Ph.D.