The lecture topics listed on this page are in their incubation stage. Some have not been given. Some have been given one or two times, as noted. The listed topics may "evolve" somewhat from talk to talk in this early stage. When a talk has been given the third time, it will be moved to the "Favored Topics" list. A brief synopsis of the talk is given below the title and the most appropriate audiences are suggested. If several titles are listed, the most recent and preferred title is listed in red. A venue listed in blue is scheduled for the near future.

Check almost any geology textbook. When it comes to the origin of the oceans and atmospheres, geologists almost uniformly agree; they originate by volcanic outgassing of the Earth's interior. Well, it makes a certain sense. Almost any volcanic eruption releases voluminous amounts of gases and water vapor. But is this new water and gases or is it recycled? After all, the oldest rocks on Earth (3.96 ga and 3.85 ga) appear to have been formed by plate tectonic processes and such long-term processes result in the subduction of surface constituents (including volatiles) deep within the mantle. Is it any surprise that these volatiles would return via volcanic eruptions? But where did such volatile constituents come from in the first place? My inclination is to think that all planets receive the bulk of their volatile constituents by comet impacts (about 67%) combined with outgassing from the interior (about 33%). Most of the volatiles collected very early in the  history of the solar system. What happened to the volatiles varied on the individual planets largely as a function of temperature and planetary mass.

This talk would be most appropriate for University Geology and Astronomy Departments. A mixture of geologists and astronomers might provoke a good discussion.

Comets which are close enough or large enough to be visible to the unaided eye appear on the average of about once every three years. However, about 20 to 30 comets below this threshold of visibility pass through the inner solar system every year. When a highly visible comet such as Hale-Bopp appears, widespread interest and/or concern is voiced. What are comets anyway? What are they made of and when and where did they form? Of what significance are they to the rest of the solar system? Do they present any danger?

I have a large number of illustrations and images of comets which I use in a wide variety of talks. I could easily arrange these illustrations in a way that could answer many of the questions raised above, paticularly if we are again visited by a spectacular comet which arrouses everyone's interest. This talk could be given at a variety of levels to any group that might be interested.

    San Diego State University: Geology Lecture Series

It is said that Venus does not have plate tectonics currently in operation, and that conclusion would probably hold true for at least the last billion years. However, in observing the older geology, particularly in the highland areas, there appear to be intensely folded rocks strongly resembling foldbelts in complex earthly collisional mountain systems such as the Appalachians. Likewise, areas having superposed compressional and extensional deformational episodes comparable to the Basin and Range Province seem best explained by plate tectonics. The major highlands areas in themselves suggest lighter subsurface rocks such as granites, although the surface may be plated over with flood basalts. A long chain of coronae could be interpreted either as a result of subduction or as a plate moving over a hot spot. Either way involves plate tectonics. To me, it looks as if Venus had plate tectonics in operation until perhaps two billion years ago when plate motion ground to a halt, perhaps because the energy necessary to run such a system dropped below a critical level. Such obvious indicators as trenches and fracture zones were subsequently filled or covered by flood basalts. Venus now seems to be operating as a celestial Lava Lamp.

This talk was originally given several years ago at SDSU and received a luke warm reception. Considerably more thought and abundant new illustrations have gone into it since that time. The talk would be best suited for University Geology Departments and might provoke considerable discussion.

    Reuben H. Fleet Science Center: Eyes on the Universe Lecture Series

Pluto has been traditionally regarded as the ninth planet. However, Pluto is tiny compared to all other planets and is even dwarfed by the Moon. Is Pluto really a planet? Or should Pluto be regarded as a "minor planet" or "trans-neptunian object"? A case can be made for either way. I would tend to continue the planet designation, at least until a voyager-type study o-is made, but I really think that Pluto will turn out to be merely a larg example of numerous objects in the Kuiper Belt and beyond.

This talk was originally given at the Fleet Center and I had mixed feelings about it. I felt it could be better on a second try. The preferred audience would probably be an astronomical society but I'd be willing to try it with other audiences. Ask and we'll discuss the matter.

The question of life elsewhere is dependent on our understanding of earthly life. It would appear that the one essential ingrediant is water. If this is correct, then the only two possibilities elsewhere in the solar system would be Mars and Europa. Mars shows clear evidence of having had liquid water in the distant past, but there is an unanswered question about the present. Europa, on the other hand, would appear to have a vast ocean of water, but the ocean is under a shell of ice many kilometers thick. Might either of these objects harbor life? Perhaps. It's a real possibility.

I've been talking about the possibility (probability?) of life getting started on Mars for several years now. I've got a couple good talks that get excellent reviews from highly diverse audiences. Recently I've added a talk regarding Europa and the possibility of life. The idea here would be to combing the two talks for a little more general audience. Anyone interested?

    San Diego Astronomy Association
    Reuben H. Fleet Science Center: Eyes on the Universe Lecture Series

Venus and the Earth are made out of the same ingrediants and are about the same size. Venus would be warmer because of a closer position to the Sun, but otherwise the two planets might be intuitively expected to be somewhat similar. But the conditions on Venus are drastically different. Venus is without water, the atmosphere is 92 times the density of that of the Earth and the surface temperature is about 500 degrees C. Furthermore, the atmosphere is 96% carbon dioxide in contrast to the Earth's 0.034% content.  The Venus surface can be observed only through the use of radar imagery, but abundant images of extraordinary quality are available. A comparison of some of the surface features of Venus and the Earth are offered.

Venus is a very interesing planet, but an explanation of it's features doesn't lend itself well to public lectures, in contrast to Mars. I put this talk together on an experimental basis and offered it to the SDAA meeting. The reaction was excellent. I'll be looking forward to trying a few other groups in the future. The Fleet Center is next.