Abstract Details
(2020) Very Organic-Rich Bodies in the Inner and Outer Solar System
Zolotov M
https://doi.org/10.46427/gold2020.3232
01c: Plenary Hall, Thursday 25th June 05:45 - 05:48
Mikhail Zolotov
View abstracts at 4 conferences in series
Listed below are questions that have been submitted by the community that the author will try and cover in their presentation. To submit a question, ensure you are signed in to the website. Authors or session conveners approve questions before they are displayed here.
Submitted by My Riebe on Sunday 21st June 07:46
For 69P the % of C is measured in the dust fraction but the comet also contains ices which presumably would reduce the total fraction of C in the comet. Is this the case also for other organic-rich objects?
Yes, C concentration in cometary ices is less than in the cometary dust. Addition of ices into the mass balance decreases bulk C concentration in a body (e.g. C/O ratio). However, C/Si ratio increases if C-bearing ices are considered and bulk cometary C/Si ratio is getting closer to the solar composition. Some organic-rich bodies, especially in the inner solar system (Ceres, Ceres-like, B and D/P asteroids) may not contain much ices. This is why we compare compositions of those bodies with ice-free cometary dust and nuclei surfaces.
For 69P the % of C is measured in the dust fraction but the comet also contains ices which presumably would reduce the total fraction of C in the comet. Is this the case also for other organic-rich objects?
Yes, C concentration in cometary ices is less than in the cometary dust. Addition of ices into the mass balance decreases bulk C concentration in a body (e.g. C/O ratio). However, C/Si ratio increases if C-bearing ices are considered and bulk cometary C/Si ratio is getting closer to the solar composition. Some organic-rich bodies, especially in the inner solar system (Ceres, Ceres-like, B and D/P asteroids) may not contain much ices. This is why we compare compositions of those bodies with ice-free cometary dust and nuclei surfaces.
Submitted by Tomohiro Usui on Thursday 25th June 02:59
Please explain more about how the “20-30 wt%” IOM fits the bulk density and surface composition of Ceres (page 8).
Ceres could contain ~10-15 wt% IOM (not 20-30 wt%, as stated in the question). Slide 8 shows a best fit for Ceres' density (2162 kg/m3) and surface composition (C content of 8-14 wt%) in the framework of [CI-type hydrated rock] - IOM (= Insoluble Organic Matter) mixture. In the figure, density of hydrated rock is a free parameter; porosity is assumed in the range of 2-8 %, IOM density is 1300 kg/m3. In that model Ceres consists of 11-15 wt% IOM (~20-30 vol% IOM), hydrated CI-type chondritic rock with density of ~2600 kg/m3, and 2-8 % porosity. Details are in Zolotov (2020, Icarus 335, 113404).
Please explain more about how the “20-30 wt%” IOM fits the bulk density and surface composition of Ceres (page 8).
Ceres could contain ~10-15 wt% IOM (not 20-30 wt%, as stated in the question). Slide 8 shows a best fit for Ceres' density (2162 kg/m3) and surface composition (C content of 8-14 wt%) in the framework of [CI-type hydrated rock] - IOM (= Insoluble Organic Matter) mixture. In the figure, density of hydrated rock is a free parameter; porosity is assumed in the range of 2-8 %, IOM density is 1300 kg/m3. In that model Ceres consists of 11-15 wt% IOM (~20-30 vol% IOM), hydrated CI-type chondritic rock with density of ~2600 kg/m3, and 2-8 % porosity. Details are in Zolotov (2020, Icarus 335, 113404).
Submitted by Brendan Chapman on Thursday 25th June 04:01
Is it your belief that the lack of C-rich materials in the inner solar system and meteorite record can be explained by thermal processing of primitive OM rather than a surplus of C-rich material in the outer solar system?
Yes, thermal decomposition of volatiles, including organic matter, could be responsible for the volatile depletion in the inner solar system seen in meteorites and terrestrial planets. Outer solar system bodies do not have a "surplus" of volatiles - the bodies (e.g. comets) are just closer to the composition of solar photosphere and present less processed material.
Is it your belief that the lack of C-rich materials in the inner solar system and meteorite record can be explained by thermal processing of primitive OM rather than a surplus of C-rich material in the outer solar system?
Yes, thermal decomposition of volatiles, including organic matter, could be responsible for the volatile depletion in the inner solar system seen in meteorites and terrestrial planets. Outer solar system bodies do not have a "surplus" of volatiles - the bodies (e.g. comets) are just closer to the composition of solar photosphere and present less processed material.
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