low temperature chemistry
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2021 ◽  
Vol 653 ◽  
pp. L5
Author(s):  
N. T. Phuong ◽  
A. Dutrey ◽  
E. Chapillon ◽  
S. Guilloteau ◽  
J. Bary ◽  
...  

Context. Molecular line surveys are among the main tools to probe the structure and physical conditions in protoplanetary disks (PPDs), the birthplace of planets. The large radial and vertical temperature as well as density gradients in these PPDs lead to a complex chemical composition, making chemistry an important step to understand the variety of planetary systems. Aims. We aimed to study the chemical content of the protoplanetary disk surrounding GG Tau A, a well-known triple T Tauri system. Methods. We used NOEMA with the new correlator PolyFix to observe rotational lines at ∼2.6 to 4 mm from a few dozen molecules. We analysed the data with a radiative transfer code to derive molecular densities and the abundance relative to 13CO, which we compare to those of the TMC1 cloud and LkCa 15 disk. Results. We report the first detection of CCS in PPDs. We also marginally detect OCS and find 16 other molecules in the GG Tauri outer disk. Ten of them had been found previously, while seven others (13CN, N2H+, HNC, DNC, HC3N, CCS, and C34S) are new detections in this disk. Conclusions. The analysis confirms that sulphur chemistry is not yet properly understood. The D/H ratio, derived from DCO+/HCO+, DCN/HCN, and DNC/HNC ratios, points towards a low temperature chemistry. The detection of the rare species CCS confirms that GG Tau is a good laboratory to study the protoplanetary disk chemistry, thanks to its large disk size and mass.


Author(s):  
Yuki Minamoto ◽  
Yuta Kondo ◽  
Kosuke Osawa ◽  
Yuji Harada ◽  
Masayasu Shimura ◽  
...  

2020 ◽  
Author(s):  
Emily Mason ◽  
Penny Wieser ◽  
Emma Liu ◽  
Evgenia Ilyinskaya ◽  
Marie Edmonds ◽  
...  

<p>The 2018 eruption on the Lower East Rift Zone of Kilauea volcano, Hawai’i released unprecedented fluxes of gases (>200 kt/d SO<sub>2</sub>) and aerosol into the troposphere [1,2]. The eruption affected air quality across the island and lava flows reached the ocean, forming a halogen-rich plume as lava rapidly boiled and evaporated seawater.</p><p>We present the at-source composition – gas and size-segregated aerosol – of both the magmatic plume (emitted from ‘Fissure 8’, F8) and the lava-seawater interaction plume (ocean entry, OE), including major gas species, and major and trace elements in non-silicate aerosol. Trace metal and metalloid (TMM) emissions during the 2018 eruption were the highest recorded for Kilauea, and the magmatic ‘fingerprint’ of TMMs (X/SO<sub>2</sub> ratios) in the 2018 plume is consistent with measurements made at the summit lava lake in 2008 [3], and with other rift and hotspot volcanoes [4,5].</p><p>We show that the OE plume composition predominantly reflects seawater composition with a small contribution from plagioclase +/- ash. However, elevated concentrations of some TMMs (Bi, Cd, Cu, Zn, Ag) with affinity for Cl-speciation in the gas phase cannot be accounted for by the silicate correction and therefore may derive from degassing of lava in the presence of elevated Cl<sup>-</sup>. In the case of silver and copper, concentrations in the OE plume are elevated above both the F8 plume and seawater.</p><p>At-vent speciation of TMMs in the F8 plume during oxidation (following a correction for ash contributions) was assessed using a Gibbs Energy Minimization algorithm (HSC chemistry, Outotec Research). We also demonstrate the sensitivity of speciation in the plume to the concentration of common ligand-forming elements, chlorine and sulfur. These results could be used as initial conditions in atmospheric reaction models to investigate how plume composition evolves as low-temperature chemistry takes over.</p><p>References:</p><p>[1] Neal C et al. (2019) Science</p><p>[2] Kern C et al. (2019) AGU Fall meeting abstract V43C-0209</p><p>[3] Mather T et al. (2012) GCA 83:292-323</p><p>[4] Zelenzki et al. (2013) Chem Geol 357:95-116</p><p>[5] Gauthier P-J et al. (2016) J Geophys 121:1610-1630</p>


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