Certain environments on Earth that host life are very similar to places on Mars and other terrestrial planets, scientists have found. So if life can exist here, why not there?
Nora Noffke is a geobiologist at Old Dominion University in Norfolk, Virginia. She has found evidence of microbial life all over the world – in both modern and in fossil coastal areas. Bacteria that grow on beach sand form microbial mats – organic layers that resemble carpets over the ground. Such carpets – composed of trillions of individual bacterial cells moving actively through the sand - leave characteristic traces in the beach deposits. We can study those traces in modern beaches of our Earth today. However, those bacterial traces also can become fossils that record ancient coast lines of the past. The oldest traces of such fossils date back to 3.2 billion years ago.
Noffke and her colleague Sherry Cady of Portland State University in Oregon recently wrote an article in the November 2009 issue of the Geological Society of America's journal, GSA Today, detailing how the melding of geology and biology can teach us about the environments most likely to host extraterrestrial life.