Is science sometimes in danger of getting tunnel vision? Recently published ebook author, Ian Miller, looks at other possible theories arising from data that we think we understand. Can looking problems in a different light give scientists a different perspective?

. Update On Planetary Accretion – May

Results from Dawn at Vesta were published in Science, but they were not especially informative, at least for theories of planetary accretion. There were data on the surface composition, which confirmed the proposition that certain meteorites came from Vesta and that Vesta differentiated. Somewhat confusing, the density was determined to be 3.456, which is not that much different from orthopyroxene, and this makes it difficult to see how the large core could be iron. It was argued that the outer layers must be very porous, suggestive of volatiles having been emitted. In this context, Vesta has strange stripes similar to those of Phobos, which also appears to have been struck on the end with an impact almost large enough to disrupt it. These results do not really add much to how Vesta formed, largely because they mainly confirm what was already “known”, and also since Vesta is very atypical for an asteroid, it may have formed elsewhere and migrated.
 
Soon Dawn will investigate Ceres. What do I expect there? While I made over 80 predictions in the ebook, I left out Ceres. If we assume, from its spherical shape, it has differentiated, my theory of its formation would suggest that the surface will probably be largely ice covered. The ice may be rich in organic material, or it may have a lot of blackish carbonaceous material, or it may be reasonably white, the variation depending on how much heat was generated in its interior for how long, which is unknowable.
 
Two theories were espoused that largely contradict my work. One argued that carbonaceous chondrites differ from ordinary chondrites because they formed earlier (Icarus, 220, 162). I argue that they are different because they formed at a different temperature in a different place. In this context, my criticism of the “earlier” theory is why did these bodies not continue accreting? The second paper (Icarus, 220, 144) proposed that the great water flows on Mars at about 3.8 Gy BP were caused by the Argyre  impactor heating the surface, giving a greenhouse atmosphere based on 6.5 bar water. Such water would not lie on the surface, and the erosion features would be due to water flowing as the heating collapsed. It is unclear to me why the water did not snow out as opposed to rain out, particularly since the Martian winter is twice as long as ours, and the south polar region is dark for this time. There is reasonably clear evidence fluid flow on Mars occurred intermittently over at least a 200 My period, and I for one cannot see how one impactor could manage that.
 
Three papers were in accord with my theory, but two would be in accord with most theories. The UV spectrum of Enceladus showed ammonia hydrate (Icarus, 220, 29). This is hardly surprising, though, and while required for my theory, it is expected from a number of others. The second was that it was proposed that the lunar basalts arose from very deep melting, in the presence of volatiles. Further, these are more localized to the nearside. This is consistent with the Theia impactor not being fully devolatalized, although again that is not specific to my theory. Finally, a paper in Nature (485, 490) proposed that there was a great geological discontinuity on Earth at about 2.5 Gy BP, and prior to this volcanic gases were more reduced. Standard theory has argued gases were always oxidized; my theory argues that all volatiles on the rocky planets were initially reduced because they had to be accreted as solids and became volatile by reaction with water (which is why Venus has more gas than Earth but essentially no water - Venus accreted less water because it was hotter and it used up almost all of it generating the atmosphere, and in subsequently oxidising it.)
 
Posted by Ian Miller on Jun 2, 2012 5:13 AM Europe/London

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