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Old 3rd December 2019, 02:37 AM   #991
jonesdave116
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Related to the previous, and in the sure belief that Sol will not be able to provide an answer, here is a little bit on hydrated minerals at asteroids;

Quote:
Hydrated silicates can be used as very sensitive tracers of thermal history (Hiroi et al., 1996). In addition to altering olivine and pyroxene to form hydrated silicates (e.g., serpentine), the aqueous alteration process produces oxidized Fe that has absorption bands in the visible and UV spectral regions. Moderate subsequent heating can alter the depth or eliminate some or all of these bands. Hiroi et al. (1996)finds that Murchison (CM2) material exhibits a strong UV band due to FeO, 0.7-μm band from Fe2+-Fe3+ charge transfer, and 3-μm band due to H2O/OH when heated less than 400°C. Between 400° and 600°C, the 0.7-μm band weakens and disappears, and the 3-μm band gets shallower. At temperatures above 600°C, the 3-μm band disappears as the minerals are completely dehydrated (Fig. 6). Asteroid 511Davida has been observed extensively, and a 3-μm band has been seen with variable depths over at least 25% of the rotation period. However, at a similar sub-Earth latitude, the 0.7-μm band was not seen at any rotation phase. A mild heating episode, occurring after the aqueous alteration, with temperatures reaching 400°–600°C, can explain these observations.
My bolding. From;

Hydrated Minerals on Asteroids: The Astronomical Record
Rivkin, A. S. et al (2002)
https://www.lpi.usra.edu/books/Aster...pdf?q=hydrated

Now, I wonder what the measured temperatures were at the above mentioned comets? Well, not even 400 K, let alone 400 C!
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