The author of Lonely Planets: The Natural Philosophy of Alien Life, David Grinspoon is a curator of astrobiology at the Denver Museum of Nature and Science as well as the first chair in astrobiology in the Kluge Center at the Library of Congress, a position he took up last November. Pat Trenner interviewed Grinspoon last August.
Air & Space: The Library of Congress announcement of your appointment says astrobiology addresses how life began and evolved and the future of life on Earth and elsewhere — pretty weighty questions. How does astrobiology begin to formulate the answers?
Grinspoon: We break it down into smaller questions that don’t weigh quite as much. In order to address how life began we study the record of life on early Earth, make predictions about what we will find on other planets and then try to test them through spacecraft missions. The future of life we can address, in part, through understanding better how planets evolve. For example, Venus may have gone through an accelerated version of Earth’s distant future when it lost its oceans to the warming sun. By deciphering this history, we may learn what is in store for us and how we will eventually need to adapt.
Any opinion on the best strategy for space exploration? Should we wait for commercial development of man-rated spacecraft or should we rely on robotic craft?
The way things are shaping up, commercial spacecraft will do the more “routine” tasks like taking cargo and humans into Earth orbit, and NASA and other government space agencies will do the more curiosity-driven, envelope-pushing exploration that can’t be expected to turn a profit any time soon, such as building large space telescopes and sending robotic craft to worlds like Venus and Titan. This makes sense to me and seems to be the way things are evolving.
Where in our solar system are we most likely to find signs of life?
We have to explore broadly because we are still profoundly ignorant about life and what it really needs. It seems obvious at least that life needs an active environment with cyclic flows of energy and matter, and probably a liquid medium where biochemistry of some kind can flourish. So I wouldn’t spend too much time or money looking for it on Mercury or the moon or asteroids. Mars is still worth exploring for life, although I think it is much more promising for possible fossil remains of early life from the time when it was more Earth-like with flowing water on the surface. My favorite places to look for life that may exist today are Saturn’s moon Titan, which has lakes of liquid methane, beneath the surface of Jupiter’s moon Europa where there is a large ocean of liquid water, and even in the clouds of Venus which are a watery, albeit chemically challenging environment. Saturn’s moon Enceladus seems to have liquid water but not necessarily the kind of globally cyclic activity that may be necessary to support a biosphere.
Would we recognize truly alien life if we found it?
I think, after a double-take or two, we would because I think life will always alter its environment in very noticeable ways, as life does on Earth.
You mention the 1989 Voyager 2-Neptune encounter, during which you watched the first close-ups of Neptune's moon, Triton, appear at the Jet Propulsion Laboratory, as a high point in your career. What is the next personal milestone you anticipate?