CompuServe Messages

Hi, Al– That unrelatedness of ureilites among themselves is indeed intriguing and suggestive. Such a variety could come from a planet, but would likely have to be ejected from the planet in many different explosions, not all in one blast. These processes for producing ureilites seem rather unusual – I doubt Venus can have an all-ureilite crust, and thus it seems there should be numerous other types of Venus rocks falling on Earth if the ureilites are such. Granite meteorites or something else of evident planetary origin would outnumber ureilites, I suspect… Counter-reservations: (1) if the method of ejection from Venus is volcanic rather than by impact, it might favor ureilites over other rocks, and (2) perhaps the unrelatedness means they came from different parts of the same vein/batholith/whatever, rather than from different veins as I am assuming, leaving us with a single Venus-ejection event. Those high pressures are impressive, but how easy is it to reach such values in a many-miles-per-second impact of two asteroids? Or were the pressures maintained too long to be from impact? I figure one should take this Venus-origin theory with a 470-km grain of salt. But ureilites could represent something even more exotic and seem quite interesting regardless. What long message? –Doug