Rosetta scientific results |
Rosetta scientific results |
Sep 12 2014, 03:33 PM
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Senior Member Group: Members Posts: 1729 Joined: 3-August 06 From: 43° 35' 53" N 1° 26' 35" E Member No.: 1004 |
This, to my knowledge, is the first refereed paper to be published on Rosetta's observations of C-G (and it's free to access!):
The rotation state of 67P/Churyumov-Gerasimenko from approach observations with the OSIRIS cameras on Rosetta |
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Dec 10 2014, 08:39 PM
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#2
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Senior Member Group: Members Posts: 1729 Joined: 3-August 06 From: 43° 35' 53" N 1° 26' 35" E Member No.: 1004 |
just out and already making noise on the social networks:
67P/Churyumov-Gerasimenko, a Jupiter family comet with a high D/H ratio QUOTE The provenance of water and organic compounds on the Earth and other terrestrial planets has been discussed for a long time without reaching a consensus. One of the best means to distinguish between different scenarios is by determining the D/H ratios in the reservoirs for comets and the Earth’s oceans. Here we report the direct in situ measurement of the D/H ratio in the Jupiter family comet 67P/Churyumov-Gerasimenko by the ROSINA mass spectrometer aboard ESA’s Rosetta spacecraft, which is found to be (5.3 ± 0.7) × 10−4, that is, ~3 times the terrestrial value. Previous cometary measurements and our new finding suggest a wide range of D/H ratios in the water within Jupiter family objects and preclude the idea that this reservoir is solely composed of Earth ocean-like water.
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Dec 11 2014, 04:47 AM
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#3
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Member Group: Members Posts: 102 Joined: 8-August 12 Member No.: 6511 |
just out and already making noise on the social networks: 67P/Churyumov-Gerasimenko, a Jupiter family comet with a high D/H ratio So here's a question. Apparently 67P was originally from the Kuiper Belt, but has been a Jupiter family comet for at least the last few centuries. A bit of googling doesn't turn up a strong estimate for when that transition occurred, though. We know that water loss by evaporation, sublimation or UV cracking can affect DE/H ratios. Could a few million years of warm/cool cycles have done this for 67P? Doug M. |
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Dec 11 2014, 06:36 AM
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#4
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Junior Member Group: Members Posts: 41 Joined: 11-April 07 From: London, U.K. Member No.: 1957 |
So here's a question. Apparently 67P was originally from the Kuiper Belt, but has been a Jupiter family comet for at least the last few centuries. A bit of googling doesn't turn up a strong estimate for when that transition occurred, though. We know that water loss by evaporation, sublimation or UV cracking can affect DE/H ratios. Could a few million years of warm/cool cycles have done this for 67P? Doug M. Yes - there is a substantial difference in vapour pressure between light and heavy water ices (Vapor pressure of ice containing D2O by Matsuo et al., 1964: 10.1126/science.145.3639.1454), which could lead to fractionation via a process such as sublimation. Indeed the fractionation factor for D2O into the ice phase increases at lower T. Since 67P gives every appearance of having a highly porous but very strong substrate, I suspect that it is a well-sintered matrix of large grains cemented together by growth from a vapour phase transported through the large (and possibly well connected network of) interstitial pores. As such, the D/H ratio may be a reflection of the degree of sintering and the thermal regime under which it occurred. |
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Dec 14 2014, 08:37 PM
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#5
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Member Group: Members Posts: 102 Joined: 8-August 12 Member No.: 6511 |
As such, the D/H ratio may be a reflection of the degree of sintering and the thermal regime under which it occurred. Thank you -- that's very interesting. If the ratio is a function of fractionation thanks to different vapor pressures, then you'd expect it to be highest where there's been most activity already, i.e. at the surface. It does make me wonder if we might see a shift in D/H as the comet gets closer to the Sun and more active. (The assumption here is that greater activity leads to outgassing from deeper inside the comet, which of course may not be the case.) Doug M. |
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