Morrison was recently honored by the world's largest organization of planetary scientists--the Division for Planetary Sciences (DPS). The DPS awarded its 2004 Carl Sagan Medal to Morrison, a former student of Sagan's.

The Sagan Medal is awarded annually to an active DPS member and researcher for their long-term excellence in communicating planetary science to the public. Morrison will receive the award at the organization's annual meeting to be held Nov. 8-12, 2004, in Louisville, Ky.

"We are honored by David's award," said G. Scott Hubbard, director of NASA Ames Research Center, Moffett Field, Calif. "A doctoral student of Carl Sagan, David is that rare breed of scientist who combines research depth with the ability to popularize technical topics to non-scientists."

Morrison has been instrumental in illuminating the scientific basis for potential hazards due to asteroid and comet impacts, through refereed papers and popular articles and books. He created and implemented the impact hazard Website.

Throughout his distinguished science career - as an expert on solar system small bodies and as an investigator for numerous spacecraft missions, including Voyager and Galileo - Morrison has dedicated himself to sharing the excitement of planetary exploration.

In his testimony to the President's blue ribbon commission "Moon To Mars and Beyond", Morrison spoke to the limits of and opportunities for scientists as "we are in that transition from being citizens of planet Earth to being citizens of the solar system."

Astrobiology Magazine (AM): In early July, the Europeans proposed what they called the "Don Quixote" mission profile for asteroid mitigation. Their scenario entails detecting a dangerous asteroid on a terrestrial collision course, then intercepting the incoming rock with a scout probe followed by a destroyer probe.

For the mission, the Europeans are soliciting international partners. Do you think this seek-and-destroy profile has a consensus among international partners as the best approach - or are there alternatives that merit consideration?

David Morrison (DM): The proposed Don Quixote mission, like the NASA Deep Impact comet mission, will certainly add to our knowledge about asteroids and comets - knowledge that will be needed if we ever have to defend against an impact.

Today we know far too little to try for a consensus as to how we would deflect an asteroid. One other approach under study is gradual deflection using a low-thrust ion engine, as proposed by the B612 Society for a follow-on Prometheus mission.

Furthermore, different targets may well require different technologies to deal with them. A number of interesting ideas that have been suggested, but not much of the hard work to actually develop these approaches has been done.

AM: That same week in early July, the Oxford English Dictionary added 'astrobiology' to their compendium. They define it as 'search for life on other planets and in space.' First how do you like to differentiate astrobiology from exobiology, as a discipline?

DM: I am glad to see "astrobiology" in the dictionary, but the definition you quote sounds more like "exobiology". Astrobiology is defined by its three theme questions, which include the origin and history of life on Earth and the future of life as well as the search for life beyond Earth - it sounds as if this is only one-third of the definition.

AM: Are there topics that astrobiology takes under its umbrella that traditionally have not been handled in exobiology literature?

DM: We might think of astrobiology as the natural evolution of exobiology. New scientific tools and concepts allow us to integrate the study of life in the universe -- for example, to link the origin and evolution of life on Earth with the identification of possible habitable worlds beyond Earth.

AM: One field that seems to wax and wane in astrobiology circles is how best to be inclusive towards climatology. For instance, the question of how to generalize the early Earth and current climate research into a broader perspective on planetary preparations to host biology?

Do you have a favorite example or illustration that highlights what a typical climate researcher may have to offer as expertise in an astrobiology survey?

DM: It seems to me that climate - especially in its long-term aspects - is intimately linked with habitability and the forces that drive evolutionary change. Studying the climate of Earth is also essential to assessing nature of other planetary atmospheres and the prospects for life there.

One of the big challenges in Earth's biological history is to understand how changes in the composition and greenhouse effect of our atmosphere may have compensated for the gradual increase in the luminosity of the Sun, thus stabilizing surface conditions.

Presumably similar challenges to habitability have acted on planets around other solar-type stars. All these issues are linked, and solving one problem may lead to insights in other related areas.

AM: Is there a breakout field that you personally think is being under-represented at astrobiology conferences or NAI partners that particularly seems intriguing to your vision for the discipline?

DM: I am pretty happy with what I see happening to astrobiology. Perhaps, however, we should be giving a greater visibility to what is likely to happen to life in the future, both on Earth and beyond the home planet, and to the ways discoveries in astrobiology may impact society.

Astrobiology has made tremendous advances since its beginning less than 10 years ago, and it is especially gratifying to see the number of young scientists who want to make a career in astrobiology.

AM: The Spaceguard Survey of Earth-approaching asteroids is supposed to be 90 percent complete by the end of 2008. Will this goal be achieved, and what (if any) follow-on program will be adopted?

DM: We are making excellent progress with the Spaceguard Survey, with more than half of the NEAs (near-Earth asteroids) larger than 1 km already discovered, and more than 3/4 of those larger than 2 km). But the field of impact studies is still too young to determine what society seeks in the way of protection, and how much they are willing to pay.

For those who mainly fear an extinction event that might end human life forever, we have already achieved a considerable level of reassurance. For those whose concern is a global, civilization-threatening disaster, we are more than halfway complete.

But for those who are primarily concerned about the smaller but more frequent impacts by sub-km NEAs, the astronomers have not achieved even 1 percent completeness in our surveys.

Last year a NASA Science Definition Team chaired by Grant Stokes of MIT recommended that future surveys be conducted, using larger telescopes, to extend down to 200m diameter asteroids.

The National Academy of Sciences has also recommended that this be done. But there is not a formal plan or commitment today to extend the surveys beyond 2008.

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