{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,11,3]],"date-time":"2025-11-03T22:51:03Z","timestamp":1762210263459},"reference-count":49,"publisher":"American Association for the Advancement of Science (AAAS)","issue":"5429","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Science"],"published-print":{"date-parts":[[1999,8,6]]},"abstract":"<jats:p>The Galileo spacecraft has detected diffuse optical emissions from Io in high-resolution images acquired while the satellite was eclipsed by Jupiter. Three distinct components make up Io's visible emissions. Bright blue glows of more than 300 kilorayleighs emanate from volcanic plumes, probably due to electron impact on molecular sulfur dioxide. Weaker red emissions, possibly due to atomic oxygen, are seen along the limbs, brighter on the pole closest to the plasma torus. A faint green glow appears concentrated on the night side of Io, possibly produced by atomic sodium. Io's disk-averaged emission diminishes with time after entering eclipse, whereas the localized blue glows brighten instead.<\/jats:p>","DOI":"10.1126\/science.285.5429.870","type":"journal-article","created":{"date-parts":[[2002,7,27]],"date-time":"2002-07-27T09:45:50Z","timestamp":1027763150000},"page":"870-874","source":"Crossref","is-referenced-by-count":65,"title":["Galileo Imaging of Atmospheric Emissions from Io"],"prefix":"10.1126","volume":"285","author":[{"given":"P. E.","family":"Geissler","sequence":"first","affiliation":[{"name":"Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85711, USA."}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"A. S.","family":"McEwen","sequence":"additional","affiliation":[{"name":"Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85711, USA."}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"W.","family":"Ip","sequence":"additional","affiliation":[{"name":"Institute of Astronomy, National Central University, Chung-Li, Taiwan 320, Republic of China."}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"M. J. S.","family":"Belton","sequence":"additional","affiliation":[{"name":"National Optical Astronomy Observatories, Tucson, AZ 85719, USA."}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"T. V.","family":"Johnson","sequence":"additional","affiliation":[{"name":"Jet Propulsion Laboratory, MS 23-201B, 4800 Oak Grove Drive, Pasadena, CA 91109, USA."}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"W. H.","family":"Smyth","sequence":"additional","affiliation":[{"name":"Atmospheric and Environmental Research, 840 Memorial Drive, Cambridge, MA 02139, USA."}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"A. P.","family":"Ingersoll","sequence":"additional","affiliation":[{"name":"Division of Geology and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA."}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"221","reference":[{"key":"e_1_3_1_2_2","unstructured":"For a comprehensive review see"},{"key":"e_1_3_1_2_3","doi-asserted-by":"publisher","DOI":"10.1006\/icar.1996.0186"},{"key":"e_1_3_1_3_2","unstructured":"Recent observations by the UV spectrometer on Galileo are reported by A. R. Hendrix C. A. Barth and C. W. Hord [ J. Geophys. Res. 104 11817 (1999)]."},{"key":"e_1_3_1_4_2","unstructured":"R. A. Brown in Exploration of the Planetary System Proceedings of the Symposium Torun Poland September 5\u20138 1973 A. Woszczyk and C. Iwaniszewska Eds. (Reidel Dordrecht Netherlands 1974) pp. 527\u2013531;"},{"key":"e_1_3_1_4_3","doi-asserted-by":"publisher","DOI":"10.1038\/258690a0"},{"key":"e_1_3_1_4_4","first-page":"468","volume":"8","author":"Trauger J. T.","year":"1976","unstructured":"Trauger J. T., et al., Bull. Am. Astron. Soc. 8, 468 (1976);","journal-title":"Bull. Am. Astron. Soc."},{"key":"e_1_3_1_4_5","doi-asserted-by":"publisher","DOI":"10.1086\/158777"},{"key":"e_1_3_1_4_6","doi-asserted-by":"publisher","DOI":"10.1086\/184016"},{"key":"e_1_3_1_5_2","doi-asserted-by":"publisher","DOI":"10.1126\/science.283.5400.353"},{"key":"e_1_3_1_6_2","doi-asserted-by":"crossref","unstructured":"Cook A. F. et al. 211 1419 (1981).","DOI":"10.1126\/science.211.4489.1419"},{"key":"e_1_3_1_7_2","doi-asserted-by":"publisher","DOI":"10.1029\/92JA00295"},{"key":"e_1_3_1_8_2","unstructured":"J. T. Trauger K. R. Stapelfeldt G. E. Ballester J. T. Clarke WFPC2 Science Team Bull. Am. Astron. Soc. 29 1002 (1997)."},{"key":"e_1_3_1_9_2","doi-asserted-by":"publisher","DOI":"10.1029\/93JE00539"},{"key":"e_1_3_1_10_2","unstructured":"M. E. Brown et al. in preparation."},{"key":"e_1_3_1_11_2","doi-asserted-by":"publisher","DOI":"10.1126\/science.274.5286.377"},{"key":"e_1_3_1_12_2","doi-asserted-by":"crossref","unstructured":"McEwen A. S. et al. 281 87 (1998).","DOI":"10.1126\/science.281.5373.87"},{"key":"e_1_3_1_13_2","unstructured":"Bandpasses listed are the wavelengths over which the system response to white light is at least 1% of the peak value for each filter to 5-nm precision [H. Breneman and K. Klaasen Report D-5880 (Jet Propulsion Laboratory Pasadena CA 1993)]."},{"key":"e_1_3_1_14_2","unstructured":"The E15 color data were recorded with exposure times (25.6 s) longer than those used in previous attempts and were telemetered with lossless compression. An earlier color sequence from orbit G7 was degraded by accidental multiple exposures."},{"key":"e_1_3_1_15_2","doi-asserted-by":"publisher","DOI":"10.1117\/1.601525"},{"key":"e_1_3_1_15_3","unstructured":". We have subtracted an empirically determined background component which was calculated as the average brightness of the region surrounding Io's disk. Brightness estimates are based on the average system response to white light over the entire bandpass of each filter. Hence line emissions may be underestimated if they occur at wavelengths near the limits of the filters' sensitivity."},{"key":"e_1_3_1_16_2","unstructured":"Total optical power is defined as 4\u03c0 JA where A is the area of the emission in square centimeters (in the image plane at the distance of the source) and J is the average measured radiance in watts per square centimeter per steradian. Power estimates assume emission at the following wavelengths: violet 404 nm; green 560 nm; red 630 nm; and clear 560 nm. Depending on the actual spectrum the sum of the power emitted in the red green and violet filters may not necessarily equal that in the clear filter [see also (14)]."},{"key":"e_1_3_1_17_2","doi-asserted-by":"publisher","DOI":"10.1006\/icar.1998.5971"},{"key":"e_1_3_1_18_2","doi-asserted-by":"publisher","DOI":"10.1029\/93JE02547"},{"key":"e_1_3_1_18_3","first-page":"980","volume":"29","author":"Ballester G. E.","year":"1997","unstructured":"Ballester G. E., et al., Bull. Am. Astron. Soc. 29, 980 (1997).","journal-title":"Bull. Am. Astron. Soc."},{"key":"e_1_3_1_19_2","doi-asserted-by":"publisher","DOI":"10.1006\/icar.1998.5972"},{"key":"e_1_3_1_20_2","unstructured":"Jupiter is surrounded by a torus-shaped cloud of trapped charged particles that rotate with the planet's magnetic field. The plasma torus is mainly made up of S and O ions and electrons that are continually being replenished by Io. The centrifugal equator of the plasma torus is inclined by \u223c7\u00b0 to Jupiter's equatorial plane so the torus wobbles with respect to Io's position every 13 hours as Jupiter rotates. Io is at maximum north and south magnetic latitudes (that is farthest from the plasma torus center) for System III magnetic longitudes of \u223c200\u00b0 and 20\u00b0 respectively and is in the magnetic equator (the densest part of the plasma torus) at \u223c110\u00b0 and 290\u00b0 respectively. Embedded within the torus is a narrow vertical band of concentrated plasma known as the \u201cribbon.\u201d The origin of this curious feature is as yet poorly known."},{"key":"e_1_3_1_21_2","unstructured":"See also R. G. Strom and N. M. Schneider in Satellites of Jupiter D. Morrison Ed. (Univ. of Arizona Press Tucson AZ 1982) chap. 16. More realistic hydrodynamic simulations [for example"},{"key":"e_1_3_1_21_3","first-page":"1121","volume":"30","author":"Austin J. V.","year":"1998","unstructured":"Austin J. V., Goldstein D. B., Bull. Am. Astron. Soc. 30, 1121 (1998);","journal-title":"Bull. Am. Astron. Soc."},{"key":"e_1_3_1_21_4","unstructured":"] produce plumes that are somewhat flatter than those shown here owing to shock pressure and horizontal flow."},{"key":"e_1_3_1_22_2","doi-asserted-by":"publisher","DOI":"10.1086\/149947"},{"key":"e_1_3_1_23_2","doi-asserted-by":"publisher","DOI":"10.1029\/98JE00632"},{"key":"e_1_3_1_23_3","unstructured":"; M. Combi K. Kabin T. Gombosi D. Dezeeuw K. Powell ibid. p. 9071; J. Saur F. M. Neubauer D. F. Strobel M. E. Summers ibid. in press."},{"key":"e_1_3_1_24_2","doi-asserted-by":"crossref","unstructured":"Possible effects of current flow through Io were described by T. Gold [ Science 206 1071 (1979)] and A. Peratt and A. Dessler [ Astrophys. Space Sci. 144 451 (1988)].","DOI":"10.1007\/BF00793198"},{"key":"e_1_3_1_25_2","doi-asserted-by":"publisher","DOI":"10.1038\/280755a0"},{"key":"e_1_3_1_25_3","doi-asserted-by":"publisher","DOI":"10.1006\/icar.1996.0125"},{"key":"e_1_3_1_26_2","doi-asserted-by":"publisher","DOI":"10.1139\/p87-074"},{"key":"e_1_3_1_27_2","doi-asserted-by":"publisher","DOI":"10.1029\/JA092iA06p05741"},{"key":"e_1_3_1_28_2","unstructured":"For electron impact excitation of Io's atmosphere in eclipse column abundances were estimated by equating the measured brightnesses to the product of a gas-column density an average electron density in the gas column and an average emission rate (for the particular brightness) that depends on the effective electron temperature in the gas column. This linear relation is approximately valid if the gas column is optically thin (not true for Na optical emissions) so that created photons may escape freely without further absorption by the gas column and if no collisional quenching occurs (not true for O optical emissions at lower altitudes). The determination of the electron temperature and density in the column is a complex problem not addressed here. Instead we adopt a range of possible values for the electron temperature (to bound the emission rate) of 40 000 K (3.4 eV) to 60 000 K (5.2 eV) and adopt nominal plasma wake values for the electron densities of 20 000 cm \u22123 for Na and O; we also correct for the brightness for the optically thick Na column. On the basis of these temperatures the emission rates assumed for Na were 5.4 \u00d7 10 \u22127 to 6.8 \u00d7 10 \u22127 photons cm 3 s \u22121 ["},{"key":"e_1_3_1_28_3","doi-asserted-by":"publisher","DOI":"10.1086\/159746"},{"key":"e_1_3_1_28_4","unstructured":"] and the rates for O were 2.4 \u00d7 10 \u22129 to 3.2 \u00d7 10 \u22129 photons cm 3 s \u22121 (D. Shemansky private communication). For SO 2 located deeper in the atmosphere an electron temperature of 40 000 K was adopted along with an electron density of 2000 cm \u22123 . An approximate electron impact excitation rate of 1.7 \u00d7 10 \u221210 photons cm 3 s \u22121 for the molecular band structures of SO 2 appropriate to the SSI violet filter was estimated from laboratory measurements (6 25) with guidance given by K. Becker (private communication)."},{"key":"e_1_3_1_29_2","unstructured":"Background plasma torus electron density as measured near Io's orbit in the plasma torus by the Voyager spacecraft is \u223c2000 cm \u22123 ["},{"key":"e_1_3_1_29_3","doi-asserted-by":"publisher","DOI":"10.1029\/93JA02908"},{"key":"e_1_3_1_30_2","unstructured":"Electron densities in the Io plasma wake as measured by the Galileo spacecraft are as high as 40 000 cm \u22123 an order of magnitude larger than the value of \u223c4000 cm \u22123 measured in the plasma torus near Io ["},{"key":"e_1_3_1_30_3","doi-asserted-by":"publisher","DOI":"10.1126\/science.274.5286.391"},{"key":"e_1_3_1_30_4","unstructured":"; L. A. Frank et al. ibid. p. 394]."},{"key":"e_1_3_1_31_2","doi-asserted-by":"publisher","DOI":"10.1029\/97GL00966"},{"key":"e_1_3_1_32_2","first-page":"1117","volume":"30","author":"Wong M. C.","year":"1998","unstructured":"Wong M. C., Smyth W. H., Bull. Am. Astron. Soc. 30, 1117 (1998);","journal-title":"Bull. Am. Astron. Soc."},{"key":"e_1_3_1_32_3","unstructured":"; in preparation."},{"key":"e_1_3_1_33_2","unstructured":"We are grateful for informative discussions with many patient colleagues before and during the Madison Wisconsin meeting of the Division for Planetary Sciences of the American Astronomical Society. Particular thanks are due to C. Alexander F. Bagenal F. Crary A. Dessler F. Herbert W. Hubbard D. Hunten K. Klaasen L. Lane M. McGrath K. Rages and N. Schneider."}],"container-title":["Science"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.science.org\/doi\/pdf\/10.1126\/science.285.5429.870","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2024,1,13]],"date-time":"2024-01-13T08:55:49Z","timestamp":1705136149000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.science.org\/doi\/10.1126\/science.285.5429.870"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1999,8,6]]},"references-count":49,"journal-issue":{"issue":"5429","published-print":{"date-parts":[[1999,8,6]]}},"alternative-id":["10.1126\/science.285.5429.870"],"URL":"https:\/\/doi.org\/10.1126\/science.285.5429.870","relation":{},"ISSN":["0036-8075","1095-9203"],"issn-type":[{"value":"0036-8075","type":"print"},{"value":"1095-9203","type":"electronic"}],"subject":[],"published":{"date-parts":[[1999,8,6]]}}}