Earliest Memory.

My earliest and most personal memory of Carl Sagan is of a time I had coffee with him in the library of the Genetics Department at Stanford Medical School. The time was the 1961-62 school year; I was a senior Biology major doing an undergraduate research project connected with Multivator, a life-detection instrument system we hoped would be part of the Viking Missions to Mars, and Carl was a visitor in Joshua Lederberg's laboratory. I think this was the first and probably the only time an astronomer has been on the faculty of a medical school.

Anyway, I was in the departmental library, where the coffee machine was located, and Carl walked in. We immediately got into a conversation about exobiology, the search for life on Mars, and prebiotic chemistry in general. He encouraged me to go into exobiology and predicted that if there were enough researchers, we might have a self-replicating system in a decade or so.

As it turned out, I didn't follow his suggestion, largely because I felt that I was much better at biology than chemistry, but since 2001, I've been working with Stanley Miller on prebiotic chemistry and with Jeffrey Bada on detecting biomarkers on Mars. Thus, after forty years, I finally took Carl's advice and got into exobiology, as I should have originally. We still don't have a self-replicating system, but impressive progress has been made with ribozymes that can copy limited stretches of RNA, so it's probably just a matter of time before we do.

This incident was an inspiration and I followed Carl's career with interest from then on, even though I spent most of my working life as a microbial geneticist and biochemist instead.

John H. Chalmers, Ph.D.