Comets- ISM connection – Day 1
Results from Rosetta have indicated some species may have interstellar inheritance.
1) O2
- Of the volatiles traced through 67Ps perihelion passage, only NH3 and O2 traced H2O activity (heliocentric dependence). All other species follow CO2.
- O2 was detect at 3.6 AU – coma density too low to be formed in coma
- However, laboratory radiation experiments of H2O2 have demonstrated that O2 is formed (up to a few percent) with H2O.
- H2O2 was detected in 67P at fairly low abundance – the heliocentric dependence of this species has not been investigated to date.
- Does H2O2 follow H2O heliocentric dependence?
- H2O2 has been detected in the ISM in a target that also has O2 and H2O (confirm?) with APEX.
What do we need to determine the origin of O2 in comets (detected in Halley and 67P only to date)?
- Need more detections of O2 in the ISM and H2O2 (with ALMA?)
- Detection of O2 and H2O2 in more comets to verify abundance and heliocentric dependence to determine if it is correlated with H2O or other volatiles. (comae chemistry?)
- Identify a source list for JWST for ISM targets and detection of O2 – preliminary surveys of H2O2 (APEX or ALMA) in targets with largest H2Oice features.
- Additional laboratory studies?
2) S2
- Observed in 3 comets
- Measured in 67P at 3.8 AU – not likely due to chemistry with low coma density at this distance.
- S2 in 67P is correlated to CO2 outgassing.
- S3 and S4 also observed and seems to have an extended source – likely from super heating of grains.
- Parent species? Grains? Gas phase seems unlikely.
- S2 is a very volatile species with short lifetime – had to be preserved in ice.
- What about the ISM? Can we identify S2 in the ISM?
Comets- ISM connection – Day 2
- Joint study of KBO and ISM region that will form comets, possible?
- TNOs are binary systems, tidal active, and to probe the origin of the ocean worlds.
- Crystalline ices in comets? Can JWST probe this? And search for crystalline silicates. Probe the ices as the comets gets activated, in particular beyond the CO activation line. Identify guest species in these ices. Detectability of ices are preferred at large rh.
- High overheads and restrictive FOR will restrict observations and follow-up during the heliocentric distances.
- Isotopic ratios, how important are the effects of opacities and low resolving powers. 13C too hard?
- Anomalous sulfur isotopic ratios in comets, depleted in the heavy ones. How is this in the ISM? They can be measured, but they only represent 1% of the total Sulphur inventory.
- NH3 follows O2 and H2O, but not CO and CO2. NH4+? NH4+ salt will not desorb in comets, it is highly refractory. ROSINA sees more NH4+ than HO3+.
- Pre-selection of ISM targets which are more favorable with JWST. Targeting the 3 microns, magnitude and star type limits when selecting sources. Spitzer surveys were not sensitive enough, JWST may open a new window.
- Are comets really pristine? Searches in quiescent clouds is restrictive, the same when looking only comets. The O2, Xenon, Sulphur values in comets indicate that formation process is probably in cold primordial environments (non-equilibrated).
- Cycling of material of cometary ices, perform laboratory experiments that would help guide the impact on cometary ices as they evolve. Re-condensed ice in comets is pure water-ice (probably crystalline).
- Does CO2 correlate with D/H? CO and CH4 vary by orders of magnitude. D/H in water and methane studies.
- Ozone in comets, HO2, H2O2, H2O but no ozone. Something in the instrument? Searches for ozone is best done by O2 singlet delta. Some over-tones may be possible.
- What heats the ices in comets? To properly guide the laboratory studies. Activation energies of reactive mixes.
- Dust source for chemical species in comets, CN? Macromolecular decomposition. Difficult to see in cores because of the temperatures. Benzene and Tholin are rather abundant. PAHs? Negatively nano-grains have been detected with Rosetta.
- Observations to support future observations with JWST? 5-8 microns with the ISM.
- Observational data to validate the carriers of the signatures in diffuse interstellar clouds.
- Distant comets with JWST.
- How big the grains will be? What processes are affecting the grains, heat-waves affecting the molecules.
