Regarding SOHO's newly announced 1st periodic comet, a guy from JPL just posted this on the Minor Planet List serve. Kind of fun to think of a comet tail made out of rock. +++++ At perihelion, the subsolar temperature on this body's surface is around 1600 K. All common silicate minerals melt by around 1200 K, so at perihelion even ordinary rocky silicates are heated to boiling and no doubt vaporizing profusely. Yes, it's a "comet" in the sense that it is no doubt giving off large amounts of vapor, but it's rock vapor, not "ice" in any sense of the word. +++++ patrick