- Email: [email protected]
Jovian magnetospheric environment science
Icarus 178 (2005) 295–296 www.elsevier.com/locate/icarus
Editorial
Jovian magnetospheric environment science The entry of the Galileo Orbiter spacecraft into Jupiter’s atmosphere in September 2003 marked a new milestone in the almost four hundred years of jovian system exploration since Galileo’s 1610 publication of the Starry Messenger communicating his sensational new telescopic discoveries of four large moons. Only after the pioneering photometric observations of Stebbins (1926) of rotational light curves of these moons did we fully understand their strong gravitational coupling to Jupiter manifested in rotations tidally locked to orbital motion. In hindsight the asymmetric surface reflectance of these moons, relatively brighter on the leading hemispheres of the inner three, might have hinted at another kind of interaction but this was not otherwise surmised until the discovery of radio emissions from Jupiter by Burke and Franklin (1955) as evidence of corotating plasma bombardment from what we now know to be the largest planetary magnetosphere in the Solar System. The present picture of this interaction, now emphasizing the jovian system as being connected by gravitational, magnetic, atmospheric, and magnetospheric plasma interactions (e.g., recent reviews in Bagenal et al., 2004), has emerged from modern spacecraft observations. A sample of these include the first Pioneer direct measurements of magnetospheric fields and trapped particles, the Voyager discovery of volcanic plumes rising from the surface of Io, Hubble Space Telescope optical detection of jovian auroral emissions, and strongly inferred presence from Galileo magnetometer, gravity, and surface imaging data of subsurface oceans for Europa, Ganymede, and Callisto. The premier importance assigned by the last decadal survey for Solar System exploration (Belton et al., 2003) to a future Europa mission arose in great part from the induction magnetic field observations as a diagnostic for a subsurface ocean and from the recognition that magnetospheric particle interactions may provide a potential energy source for life within the ocean. In addition to the moon–magnetosphere interactions internal to the system, the hugely extended jovian magnetosphere interacts with the interplanetary solar wind plasma and manifests this external interaction through auroral activity correlated to the solar wind variations. Accordingly, the Science Definition Team (Greeley et al., 2004) for the now-deferred Jupiter Icy Moons Orbiter (JIMO) identified jovian system interactions as one of three overarching themes for JIMO and recognized that these interactions are intimately coupled to the other two themes, the search for liquid subsurface water and for chemical signs of life. 0019-1035/$ – see front matter 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.icarus.2005.08.004
In the aftermath of the Galileo Orbiter mission, and in the midst of JIMO mission planning, we organized the special sessions entitled “Jovian Magnetospheric Environment Science for the Jupiter Icy Moons Orbiter (JIMO)” for the Fall 2003 Meeting of the American Geophysical Union in San Francisco. These sessions included invited and contributed presentations related to the jovian magnetosphere and its interactions with the Galilean moons, the Io torus, Amalthea, auroral regions in Jupiter’s upper atmosphere, and the external solar wind environment of the Jupiter system. In soliciting these presentations we were looking for works that would contribute to science planning for future missions to Jupiter including but not limited to JIMO. The present set of papers was solicited from the AGU session and other contributors on interactions of any component of the jovian magnetosphere with the moons, rings, and atmosphere of Jupiter. The scope of the solicitation extended from interaction of magnetic fields, plasma and energetic charged particles, neutral atoms, dust, and electromagnetic waves with solid surfaces or atmospheres, to chemical, geological, or astrobiological effects at these interaction sites, and to mass and energy transfer from these locations into the magnetospheric environments and beyond. We also solicited works on innovative new techniques for future measurements in the jovian system and on reference models derived from existing data and future measurements directly related to, or affected by, the magnetospheric interactions. The following collection of ten papers reflects the diverse and broad nature of this field. The presentations comprise one on the theory of a fundamentally new technique exploiting the Hanle effect (Ben-Jaffel et al.) for remote measurement of Jupiter’s surface magnetic field, two on correlative observations (Pryor et al., Ajello et al.) of the jovian aurora and the solar wind during the Cassini flyby on December 2000, three on mass injection into the magnetosphere respectively from Io volcanism (Takahashi et al.) and Europa’s surface-bound atmosphere (Eviatar and Paranicas, Leblanc et al.), two on statistical modeling of the energetic particle environment (Jun et al., Sorenson et al.) for application to moon interactions and radiation hazard assessment for future missions, one on energetic particle and plasma wave measurements in the source region of energetic precipitation into the jovian auroral zone (Bhattacharya et al.), and one on high-resolution X-ray spectroscopy (Elsner et al.) as a future technique for remote compositional measurements of
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J.F. Cooper, K.K. Khurana / Icarus 178 (2005) 295–296
the moon surfaces, the Io plasma torus, and the auroral zones. The Hanle effect work is timely since NASA has assigned high priority to mapping of the jovian planetary magnetic field and polar magnetosphere with the selected Juno polar orbiter mission due to launch by 2010. The Cassini correlative analysis papers point to the great potential of future flybys, e.g., by New Horizons in early 2007 enroute through the jovian system to Pluto. Mass transfer into the magnetosphere and between the Galilean moons is further illuminated by the Io and Europa papers on atmospheric losses which would be more fully revealed for Europa by a future orbiter mission in lieu of JIMO. The magnetospheric radiation environment papers support reference model development for physics-driven understanding of moon–magnetosphere and atmosphere–magnetosphere interactions. Finally the X-ray spectroscopy paper illuminates the technique of moon surface composition measurements from X-rays produced by the intense surface irradiation. Ironically, the magnetospheric irradiation limits survival of recognizable biochemical signs of life on the moon surfaces but at the same time enables measurements of the associated inorganic and elemental chemical composition. These papers provide more detailed examinations of some of the broad range of topics addressed by oral and poster presenters at the Fall 2003 AGU special sessions. We thank the American Geophysical Union for hosting these sessions and the editors and staff of Icarus for support in publication of this related set of papers. We hope that these and other published or emerging works from the initial age of jovian system exploration will point the way for future in situ spacecraft and remote Earth-based telescopic surveys to achieve an intimate understanding of the formative processes and interactions within this complex system. Continuing investigations of the jovian system
also provide reference models in the ongoing intensive search for extrasolar planets and for potential alternatives to terrestrial planets as abodes for life in the Universe. References Bagenal, F., McKinnon, W.B., Dowling, T.E. (Eds.), 2004. Jupiter—The Planet, Satellites, and Magnetosphere. Cambridge Univ. Press, Cambridge, UK. Belton, M.J.S., 56 colleagues, 2003. New Frontiers in the Solar System—An Integrated Exploration Strategy. Space Studies Board, National Academy of Sciences, National Academies Press, Washington, DC. Burke, B.F., Franklin, K.L., 1955. Observations of a variable radio source associated with the planet Jupiter. J. Geophys. Res. 60, 213–217. Greeley, R., 37 colleagues, 2004. Report of the NASA Science Definition Team for the Jupiter Icy Moons Orbiter (JIMO). NASA Headquarters, Feb. 13. Stebbins, J., 1926. The light variations of the satellites of Jupiter and their application to measures of the solar constant. Publ. Astron. Soc. Pacific 38 (225), 321–322.
John F. Cooper Space Physics Data Facility, Code 612.4, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA E-mail address: [email protected] Krishan K. Khurana Institute of Geophysics and Planetary Physics, University of California—Los Angeles, Los Angeles, CA 90095, USA E-mail address: [email protected] Available online 23 September 2005
Editorial
Jovian magnetospheric environment science The entry of the Galileo Orbiter spacecraft into Jupiter’s atmosphere in September 2003 marked a new milestone in the almost four hundred years of jovian system exploration since Galileo’s 1610 publication of the Starry Messenger communicating his sensational new telescopic discoveries of four large moons. Only after the pioneering photometric observations of Stebbins (1926) of rotational light curves of these moons did we fully understand their strong gravitational coupling to Jupiter manifested in rotations tidally locked to orbital motion. In hindsight the asymmetric surface reflectance of these moons, relatively brighter on the leading hemispheres of the inner three, might have hinted at another kind of interaction but this was not otherwise surmised until the discovery of radio emissions from Jupiter by Burke and Franklin (1955) as evidence of corotating plasma bombardment from what we now know to be the largest planetary magnetosphere in the Solar System. The present picture of this interaction, now emphasizing the jovian system as being connected by gravitational, magnetic, atmospheric, and magnetospheric plasma interactions (e.g., recent reviews in Bagenal et al., 2004), has emerged from modern spacecraft observations. A sample of these include the first Pioneer direct measurements of magnetospheric fields and trapped particles, the Voyager discovery of volcanic plumes rising from the surface of Io, Hubble Space Telescope optical detection of jovian auroral emissions, and strongly inferred presence from Galileo magnetometer, gravity, and surface imaging data of subsurface oceans for Europa, Ganymede, and Callisto. The premier importance assigned by the last decadal survey for Solar System exploration (Belton et al., 2003) to a future Europa mission arose in great part from the induction magnetic field observations as a diagnostic for a subsurface ocean and from the recognition that magnetospheric particle interactions may provide a potential energy source for life within the ocean. In addition to the moon–magnetosphere interactions internal to the system, the hugely extended jovian magnetosphere interacts with the interplanetary solar wind plasma and manifests this external interaction through auroral activity correlated to the solar wind variations. Accordingly, the Science Definition Team (Greeley et al., 2004) for the now-deferred Jupiter Icy Moons Orbiter (JIMO) identified jovian system interactions as one of three overarching themes for JIMO and recognized that these interactions are intimately coupled to the other two themes, the search for liquid subsurface water and for chemical signs of life. 0019-1035/$ – see front matter 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.icarus.2005.08.004
In the aftermath of the Galileo Orbiter mission, and in the midst of JIMO mission planning, we organized the special sessions entitled “Jovian Magnetospheric Environment Science for the Jupiter Icy Moons Orbiter (JIMO)” for the Fall 2003 Meeting of the American Geophysical Union in San Francisco. These sessions included invited and contributed presentations related to the jovian magnetosphere and its interactions with the Galilean moons, the Io torus, Amalthea, auroral regions in Jupiter’s upper atmosphere, and the external solar wind environment of the Jupiter system. In soliciting these presentations we were looking for works that would contribute to science planning for future missions to Jupiter including but not limited to JIMO. The present set of papers was solicited from the AGU session and other contributors on interactions of any component of the jovian magnetosphere with the moons, rings, and atmosphere of Jupiter. The scope of the solicitation extended from interaction of magnetic fields, plasma and energetic charged particles, neutral atoms, dust, and electromagnetic waves with solid surfaces or atmospheres, to chemical, geological, or astrobiological effects at these interaction sites, and to mass and energy transfer from these locations into the magnetospheric environments and beyond. We also solicited works on innovative new techniques for future measurements in the jovian system and on reference models derived from existing data and future measurements directly related to, or affected by, the magnetospheric interactions. The following collection of ten papers reflects the diverse and broad nature of this field. The presentations comprise one on the theory of a fundamentally new technique exploiting the Hanle effect (Ben-Jaffel et al.) for remote measurement of Jupiter’s surface magnetic field, two on correlative observations (Pryor et al., Ajello et al.) of the jovian aurora and the solar wind during the Cassini flyby on December 2000, three on mass injection into the magnetosphere respectively from Io volcanism (Takahashi et al.) and Europa’s surface-bound atmosphere (Eviatar and Paranicas, Leblanc et al.), two on statistical modeling of the energetic particle environment (Jun et al., Sorenson et al.) for application to moon interactions and radiation hazard assessment for future missions, one on energetic particle and plasma wave measurements in the source region of energetic precipitation into the jovian auroral zone (Bhattacharya et al.), and one on high-resolution X-ray spectroscopy (Elsner et al.) as a future technique for remote compositional measurements of
296
J.F. Cooper, K.K. Khurana / Icarus 178 (2005) 295–296
the moon surfaces, the Io plasma torus, and the auroral zones. The Hanle effect work is timely since NASA has assigned high priority to mapping of the jovian planetary magnetic field and polar magnetosphere with the selected Juno polar orbiter mission due to launch by 2010. The Cassini correlative analysis papers point to the great potential of future flybys, e.g., by New Horizons in early 2007 enroute through the jovian system to Pluto. Mass transfer into the magnetosphere and between the Galilean moons is further illuminated by the Io and Europa papers on atmospheric losses which would be more fully revealed for Europa by a future orbiter mission in lieu of JIMO. The magnetospheric radiation environment papers support reference model development for physics-driven understanding of moon–magnetosphere and atmosphere–magnetosphere interactions. Finally the X-ray spectroscopy paper illuminates the technique of moon surface composition measurements from X-rays produced by the intense surface irradiation. Ironically, the magnetospheric irradiation limits survival of recognizable biochemical signs of life on the moon surfaces but at the same time enables measurements of the associated inorganic and elemental chemical composition. These papers provide more detailed examinations of some of the broad range of topics addressed by oral and poster presenters at the Fall 2003 AGU special sessions. We thank the American Geophysical Union for hosting these sessions and the editors and staff of Icarus for support in publication of this related set of papers. We hope that these and other published or emerging works from the initial age of jovian system exploration will point the way for future in situ spacecraft and remote Earth-based telescopic surveys to achieve an intimate understanding of the formative processes and interactions within this complex system. Continuing investigations of the jovian system
also provide reference models in the ongoing intensive search for extrasolar planets and for potential alternatives to terrestrial planets as abodes for life in the Universe. References Bagenal, F., McKinnon, W.B., Dowling, T.E. (Eds.), 2004. Jupiter—The Planet, Satellites, and Magnetosphere. Cambridge Univ. Press, Cambridge, UK. Belton, M.J.S., 56 colleagues, 2003. New Frontiers in the Solar System—An Integrated Exploration Strategy. Space Studies Board, National Academy of Sciences, National Academies Press, Washington, DC. Burke, B.F., Franklin, K.L., 1955. Observations of a variable radio source associated with the planet Jupiter. J. Geophys. Res. 60, 213–217. Greeley, R., 37 colleagues, 2004. Report of the NASA Science Definition Team for the Jupiter Icy Moons Orbiter (JIMO). NASA Headquarters, Feb. 13. Stebbins, J., 1926. The light variations of the satellites of Jupiter and their application to measures of the solar constant. Publ. Astron. Soc. Pacific 38 (225), 321–322.
John F. Cooper Space Physics Data Facility, Code 612.4, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA E-mail address: [email protected] Krishan K. Khurana Institute of Geophysics and Planetary Physics, University of California—Los Angeles, Los Angeles, CA 90095, USA E-mail address: [email protected] Available online 23 September 2005