Geobiologist Kenneth Nealson to discuss the search for life on other planets in public lecture on Thursday, October 16, at UC Santa Cruz

If life exists on Mars, how would we know? Scientists have been grappling with this deceptively simple question for years. Kenneth Nealson, the Wrigley Professor of Geobiology at the University of Southern California, is a leading authority on this issue, which he will address in a public lecture at the University of California, Santa Cruz, on Thursday, October 16.

Nealson's talk is the third Halliday Lecture, a public lecture series sponsored by the UCSC Department of Astronomy and Astrophysics and the UC Observatories/Lick Observatory. The lecture, "Recognizing Life Under Strange and Distant Rocks," begins at 8 p.m. in the Music Center Recital Hall on the UCSC campus. It is free and open to the public.

Nealson is a recognized pioneer of the young interdisciplinary field of geobiology, which studies the interrelation between the chemistry of life and the mineral and metal composition of the Earth. His recent interests have been directed toward the microbiology of life in extreme environments. He has chaired several NASA task groups charged with evaluating techniques in the search for nonterrestrial life in the solar system, particularly on Mars.

The basic proposition is this: If you have a rock from Mars, or any other extraterrestrial site, what can you do to decide if life is, or ever was, present? Life on other planets may take forms completely unlike those on Earth. But scientists can use physical and chemical measurements to search for things that "shouldn't be there," Nealson says. This inferential method may be necessary for finding unknown extraterrestrial life forms, and it involves a decidedly nonbiological approach, he says.

At USC, Nealson is affiliated with the Departments of Earth Sciences and Biological Sciences. Before joining the USC faculty in 2001, he was a senior scientist at the Jet Propulsion Laboratory in Pasadena.

The Halliday Lecture Series is made possible through the generous support of John Halliday to promote public awareness and appreciation for astronomy and astrophysics.