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Abstract The dominant form of oxygen in cold molecular clouds is gas-phase carbon monoxide (CO) and ice-phase water (H2O). Yet, in planet-forming disks around young stars, gas-phase CO and H2O are less abundant relative to their interstellar medium values, and no other major oxygen-carrying molecules have been detected. Some astrochemical models predict that gas-phase molecular oxygen (O2) should be a major carrier of volatile oxygen in disks. We report a deep search for emission from the isotopologue16O18O (NJ= 21− 01line at 233.946 GHz) in the nearby protoplanetary disk around TW Hya. We used imaging techniques and matched filtering to search for weak emission but do not detect16O18O. Based on our results, we calculate upper limits on the gas-phase O2abundance in TW Hya of (6.4–70) × 10−7relative to H, which is 2–3 orders of magnitude below solar oxygen abundance. We conclude that gas-phase O2is not a major oxygen carrier in TW Hya. Two other potential oxygen-carrying molecules, SO and SO2, were covered in our observations, which we also do not detect. Additionally, we report a serendipitous detection of the C15NNJ= 25/2− 13/2hyperfine transitions,F= 3 − 2 andF= 2 − 1, at 219.9 GHz, which we found via matched filtering and confirm through imaging.
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Magmatic Carbon and Helium in Springs Reveals the Vitality of a Dormant Volcano, Taranaki, New Zealand
Abstract A challenge in monitoring long‐dormant volcanoes is to discover early signs of reawakening. Mineral springs on Taranaki volcano (2,518 m, New Zealand) have elevated carbonate concentrations, δ13CDIC ∼ −5‰ (VPDB) and He isotopes from 5.13 to 5.92 RA, indicating a magmatic volatile source. Stable isotopes demonstrate water recharge occurs near the volcano's summit. Volatile anions and silica are low in a cold (5oC) flank spring at 1,000 m a.s.l., yet elevated in warm springs (25–32oC) associated with travertine deposits at 250–300 m, suggesting a weak hydrothermal component along the flow path. Tritium dating of the cold spring water yields a mean residence time of 7.8 years. This short residence time and magmatic volatile signatures suggest magmatic CO2persistently flushes Taranaki's upper edifice. Cold spring geochemistry thus reveals volcanic activity at this dormant volcano that otherwise lacks obvious geophysical signs of unrest.
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- PAR ID:
- 10444030
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 49
- Issue:
- 18
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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