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?

Planetary Formation Update, And A Challenge.

As I haven't updated for some time, there should be a lot of references summarized, however, many of them turned out to be only of partial interest. There were a few papers discussing the origin of chondrules. Up until recently, while the formation of these had been something of a mystery, the nearest there was to a conclusion was that they were formed in the plume formed by collisions of planetesimals. Fu et al. (Science 346: 1089 – 1092) found that chondrules in one meteorite formed at about 2 – 3 My after the first small bodies. This was supported by Palme, et al. (Earth Planet. Sci. Lett. 411: 11 – 19.) who found that chondrules behaved as if they were formed before any larger bodies, and were not formed by impacts. On the other hand, Johnson et al. (Science 517: 339 – 341) argued that chondrules in CB chondrites probably formed in a plume produce by an impact at a relative velocity of greater than 10 kilometers per second. If so, meteorites are a byproduct of planet formation rather than left-over building material. Of course there may have been more than one route that lead to their formation, but as can be seen, there is no clear answer to this question yet.
 
The landing on the Jupiter family comet 67P/Churyumov-Gerasimenko probably attracted as much recent public interest as anything in science, and some data are coming in. Examination of the comet's water (Altweg et al. Science 347: 126952-1 to 3) showed that the comet had a D/H ratio that is three times greater than Earth's water, and hence Jupiter family comets could not be a significant source of Earth's water. The reason this is important is that the water has to come from somewhere, and comets were once considered the obvious source. However, the usual distant comets were found to have too much deuterium, so Jupiter-family comets became the choice. The alternative is carbonaceous chondrites, but the problem with these is they are rather rare, and lie on the outer part of the asteroid belt. Had they been the source, why were there so many of them, and so few of what are now the more common asteroids? And if there were that many, why did they not accrete into a small planet? In my theory, neither comets nor chondrites are significant sources of water on earth.
 
 Meanwhile, spectral data of the surface of the comet was compatible with the presence of opaque minerals associated with non-volatile organic material with C-H and O-H bonds, but with very little contribution from N-H bonds (Capaccioni et al. 2015. Science aaao628 – 1 to 5.). There may have been small amounts of ice, but no ice-rich patches and the surface was generally dehydrated. Similarly, (Hassig et al. 2015 Science 347: aaa0276-1 to 4) showed the outgassing comprised water, CO and CO2. The relevance here is the absence of significant amounts of nitrogen-containing compounds, as required by my theory of planetary formation, as long as the body did originate in the Jovian region. That is pleasant support, even though the supporters do not realize it.
 
Significant results are beginning to come in from Gale crater, on Mars. Of particular interest to me was that from Bridges et al. 2015 (J. Geophys. Res.: Planets: 10.1002/2014JE004757). The clays found at Gale crater was consistent with the basalt having reacted with a fluid of pH between 7.5 and 12, and further, the reactions did not occur in a setting where exchange with an overlying CO2 atmosphere was possible because had it been so, there would have been deposits of carbonates, and there were not. My theory involved an early methane atmosphere with ammonia in the local water, although of course Gale crater may not be a good example of early Mars, as impact craters could have their own localized geology. Nevertheless, overall all these facts are in accord with what I published, and nothing has been found that contradicts it, so I am tolerably happy.
 
On a more personal level, on March 4 I have been asked by the Wellington Astronomical Society to give a talk, and include some chemistry. Accordingly, I chose "Origin of life" as a topic and have put out an abstract and issued two challenges, which readers here may as well join in.
1.     Why did nature choose ribose for nucleic acids?
2.     How did homochirality arise?
Put your guesses or inspired knowledgeable comments at the end of this post. The answers are not that difficult, but they are subtle. I shall post my answers in due course. In the meantime, I am offering serious discounts on my ebook "Planetary Formation and Biogenesis" from Amazon (US and UK only) from March 6 for about six days, the discount abating over time, so get in early. (Sorry about that commercial intrusion.)
Posted by Ian Miller on Feb 16, 2015 2:21 AM Europe/London

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