| 1. |
- Moullet, Arielle, et al.
(författare)
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Distribution of alkali gases in Io's atmosphere
- 2015
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Ingår i: American Astronomical Society, Division of Planetary Sciences Meeting 47. ; 47, s. 311.31-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Thanks to high-sensitivity (sub)millimeter spectroscopic observations, KCl and NaCl in gas phase have been detected at low concentration levels in Io's atmosphere. These molecules are likely to be the main potassium and sodium carriers from the moon to its environment. Indeed, potassium and sodium are known to be present in Io's neutral clouds and plasma torus, which are believed to be fed from the moon itself.The immediate sources of gaseous NaCl and KCl in Io's atmosphere are still unknown. Based on thermochemical arguments, both molecules could be present in volcanic plumes. Their lifetime in gaseous form is predicted to be rather low (a few hours), and a large portion of the emitted gas should quickly condense on the ground. Sputtering of surface condensates by high-energy particles may re-inject some of the condensates back in the atmosphere. The efficiency of this process is highly dependant on the local atmospheric column density.We present maps of NaCl and KCl emission distribution, obtained in 2012 and 2015 with the Atacama Large Millimter Array (ALMA). The distribution maps will be compared to the distribution of volcanic centers and Io's bulk atmosphere (SO2), in an attempt to characterize their immediate sources.
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| 2. |
- Roth, Lorenz, et al.
(författare)
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An attempt to detect transient changes in Io's SO2 and NaCl atmosphere
- 2020
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Ingår i: Icarus. - : Elsevier BV. - 0019-1035 .- 1090-2643. ; 350
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Tidskriftsartikel (refereegranskat)abstract
- Io's atmosphere is predominately SO2 that is sustained by a combination of volcanic outgassing and sublimation. The loss from the atmosphere is the main mass source for Jupiter's large magnetosphere. Numerous previous studies attributed various transient phenomena in Io's environment and Jupiter's magnetosphere to a sudden change in the mass loss from the atmosphere supposedly triggered by a change in volcanic activity. Since the gas in volcanic plumes does not escape directly, such causal correlation would require a transient volcano-induced change in atmospheric abundance, which has never been observed so far. Here we report four observations of atmospheric SO2 and NaCl from the same hemisphere of Io, obtained with the IRAM NOEMA interferometer on 11 December 2016, 14 March, 6 and 29 April 2017. These observations are compared to measurements of volcanic hot spots and Io's neutral and plasma environment. We find a stable NaCl column density in Io's atmosphere on the four dates. The SO2 column density derived for December 2016 is about 30% lower compared to the SO2 column density found in the period of March to April 2017. This increase in SO2 from December 2016 to March 2017 might be related to increasing volcanic activity observed at several sites in spring 2017, but the stability of the volcanic trace gas NaCl and resulting decrease in NaCl/SO2 ratio do not support this interpretation. Observed dimmings in both the sulfur ion torus and Na neutral cloud suggest rather a decrease in mass loading in the period of increasing SO2 abundance. The dimming Na brightness and stable atmospheric NaCl furthermore dispute an earlier suggested positive correlation of the sodium cloud and the hot spot activity at Loki Patara, which considerably increased in this period. The environment of Io overall appears to be in a rather quiescent state, preventing further conclusions. Only Jupiter's aurora morphology underwent several short-term changes, which are apparently unrelated to Io's quiescent environment or the relatively stable atmosphere.
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