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

My alternative theory survived August! I found no papers that falsified the major premises, although one paper would have led me to change slightly what I wrote. The good news is that it far more strongly falsifies the standard position. This paper (Hirschmann et al., Earth Planet. Sci. Lett. 3465-348: 38-48.) demonstrated that molecular hydrogen is significantly more soluble in molten silicates when under pressure than had previously been realized. The standard theory is that early silicates were oxidized, the logic being:
(a) Modern volcanoes emit oxidized gases.
(b) Modern and ancient volcanic silicates have a similar composition.
(c) Therefore, ancient volcanic gases were oxidized (CO2 and N2)
My argument is that (c) does not follow. The “oxidation state” is not a valid variable (it is conserved in a closed system) and that the nature of silicates is determined by the free energy and depends on the local temperature and pressure, and on the movement of matter between phases. In this context, the major silicates in volcanic rock are olivines and pyroxenes, with the iron being present in the ferrous state. At much higher pressures (deeper) ferrous silicates disproportionate into ferric and iron, and so such cations in a rock do not indicate much except the local conditions when the rock crystallized.
The significance of this lies in the nature of the original atmosphere. Standard theory says “oxidized gases”; my argument was some reduced gases, which were generated when carbonaceous material (see my previous blog, “Carbonaceous Mars”) reacted with water thus producing CO and H2 (syngas) and when iron reacted with water to make ferrous or, if deep enough, ferric hydroxide and hydrogen gas. The hydrogen is critical for making some of the molecules that are critical for biogenesis, and to some extent these would be more difficult to make if hydrogen escaped rapidly to space. Evidence that hydrogen would dissolve in silicates meant that it would be available for further synthesis for a longer time. Magma can take a Gy to move 1000 km upwards.
This does not mean that my argument must be right, but at least it makes it more plausible, in which case the production of the precursors to life is not an extraordinarily unlikely event at all, but is probable on any Earth-like planet (Earth-like being defined as being of comparable size and having massive granitic cratons). What is “comparable”? The range of sizes is unclear, and this makes Mars a fascinating exploration site. Will Curiosity find clues to biogenetic material? We do not know yet; if there is any remaining on Mars it has to be protected from the ionizing radiation, so it will have to be buried. Digging is a problem, because digging has to be in the correct place and be deep enough. We await results.
Posted by Ian Miller on Sep 4, 2012 12:50 AM Europe/London

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