Life on Mars?
Mars may have been a more favorable planet for life to get started. The bombardment of the planets by asteroids and comets can eject rocks into space, providing a mechanism for microbes to be transported from Mars to Earth (or vice versa). Mars meteorites are known on Earth. Today the surface of Mars is a freeze-dried desert; any extant life would probably lie deep underground. I am investigating the plausibility of the above scenario, and seeking additional evidence to support the "Mars first" hypothesis. This subject forms the central theme of my book The Fifth Miracle / The Origin of Life.
Nature of Life
Definitions of life are notoriously contentious. I am developing a new line of attack based on the notion of life as an information processing and replicating system, i.e. stressing the software over the hardware aspects. This entails trying to understand how information processing and autonomy system can emerged in an uniformed system.
Origin of Life
This is the Big Problem, and one of the outstanding challenges to science. I have a hunch that quantum physics played a role in this transition, and I'm investigating a number of mathematical models to determine if and when quantum mechanics can play a non-trivial role. I am also using computer models of cellular automata with novel types of dynamics to try to capture the elusive notion of emergent complexity in a rigorous way.
Are We Alone? The Search for Life in the Universe
So far, there is no direct scientific evidence for any life beyond Earth. The possibility that life might be widespread in the universe hinges on how easy it is to emerge from non-life - the big unknown discussed in the foregoing section. For my own thinking, see Wild ideas I like to think about.