Hi,
I saw some comments on this board that relate to my abstract for the DPS meeting. I call it my "Oceans 11" paper, since that's the number I come up with for outerplanetary water-based oceans. The BBC added some texture not included in the abstract, at http://news.bbc.co.uk/1/hi/sci/tech/2290005.stm. The general idea is that the small outerplanetary bodies like Pluto and Triton (and not so small like Ganymede and Titan) are made up of ice and rock. The rock has sunk to the middle of the body. Since the rock is slightly radioactive, it gives off heat, which, for Titan, is on the order of 100,000 megawatts. If, at the interface of the ice and rock, the temperature is greater than the melting point of the ice (and opinions vary on this temperature), then an ocean can be present. Long ago, the radioactivity rates were higher than today, so the occurrence of oceans then was more likely than their occurrence now. Pluto and Triton were likely to have formed oceans in the past, and may have sufficient radioactivity today to maintain the oceans. For simplicity, clarity, and for maintaining a direct comparison among the many bodies studied, I ignored tidal and other heating sources. Of course, they make oceans even more likely. Charon, before it became synchronous with Pluto, would have helped Pluto form the ocean. The chief unknown is the rate of radioactive heating. I used a present-day value based on values for stoney meteorites. Samples from the Moon taken by Apollo astronauts, however, have twice this value, so there might be twice the internal heating as I have assumed. If so, oceans are quite common in the outer solar system, the Kuiper belt, and even the Oort cloud. Chris p.s. I don't argue about the thickness of the crusts, but my calcs suggest thicknesses of 66, 85 and 75 km for Europa, Callisto and Ganymede, respectively. These numbers are not authoritative, but might be somewhat defensible. Christopher England Technologist, New Millennium Program Thermal and Propulsion Engineering Section Jet Propulsion Laboratory == You are subscribed to the Europa Icepick mailing list: [EMAIL PROTECTED] Project information and list (un)subscribe info: http://klx.com/europa/
