The idea to organize a conference on the origin of the Moon sprang forth during a meeting in the spring of 1982 of the Lunar and Planetary Sample Team (nicknamed LAPST) at the Lunar and Planetary Institute in Houston. LAPST was a committee that advised NASA about allocating lunar samples to researchers, but also tried to ensure the vitality of lunar science by organizing a series of workshops and topical conferences over a period of several years. We were brainstorming about what workshop or conference to hold next, when someone, I think it was Gunter Lugmair (University of California, San Diego), said, "Why not a conference on the origin of the Moon?" Everyone latched right on to the idea, and I was nominated to organize it. We thought about other scientists to convene it with me, and easily narrowed it down to Roger Phillips, a geophysicist, and Bill Hartmann, an astronomer and impact expert. None of us suspected that it would be Bill Hartmann's hypothesis for the Moon's origin that would emerge as the dominant one after the conference. Roger, Bill, and I later chose the rest of the organizing committee (see list below).
We then had to decide where and when to hold the conference. To save precious travel money and attract attendees, we decided to attach it to a meeting of the Division of Planetary Sciences (DPS) of the American Astronomical Society. The next DPS meeting was scheduled six months later in Ithaca, New York. "Too soon," someone said, and we all agreed. "Where's the next DPS meeting?" I looked at a schedule I had been given by a staff member of the Lunar and Planetary Institute. I smiled. "October, 1984, in Hawaii," I said. There were smiles and nods all around, with thoughts of white beaches and azure blue sea in our heads. Who could resist? The first notices about the conferences went out well over a year before the event, giving lots of time for scientists all over the world to work on the problem.
The conference was revolutionary. The traditional ideas for lunar origin were tossed aside by almost all attendees in favor of the giant impact hypothesis. Beyond the giant impact hypothesis being a good idea, several factors came into play to raise it to its pedestal. The three old ideas (fission from the Earth, capture, and binary accretion) had their adherents, but most of us were dissatisfied with all of old hypotheses. Each had serious flaws. Computer methods had improved significantly, so simulations of the giant impact could be done. Our understanding of impact processes was stronger than ever because of experiments and studies of large terrestrial craters. Finally, and perhaps most important, our ideas of how planets accumulated had achieved a new paradigm that depicted planets accumulating from objects that were themselves still accumulating, leading to several large bodies near each other. In this view, a giant impact was almost certain to happen. At the end of the three-day conference, the traditional hypotheses were discarded by most of us-a revolution in our thinking!
The 1998 conference in Monterey was quite different. Although some participants raised doubts about the evidence for the giant impact, the extent of melting in the early Earth, and how the Earth's core formed, the giant impact idea was central to almost everyone's thinking. It provides the context in which we think about planet formation, much the way plate tectonics provides the context in which we try to understand the geology of the Earth.
A book stemming from the conference appeared about a year and a half after the conference:
Conveners:
Program committee:
William V. Boynton (University of Arizona)
Alan Harris (Jet Propulsion Laboratory)
Lon L. Hood (University of Arizona)
Pamela Jones (Lunar and Planetary Institute)
Gunter W. Lugmair (University of California, San Diego)
Graham Ryder (Lunar and Planetary Institute)
RETURN to "Origin of the Earth and Moon", in PSRD December 1998 issue.