Michael R. Combi

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The Cassini spacecraft passed within 168.2 kilometers of the surface above the southern hemisphere at 19:55:22 universal time coordinated on 14 July 2005 during its closest approach to Enceladus. Before and after this time, a substantial atmospheric plume and coma were observed, detectable in the Ion and Neutral Mass Spectrometer (INMS) data set out to a(More)
The plasma environment of comet 67P/Churyumov-Gerasimenko, the Rosetta mission target comet, is explored over a range of heliocentric distances throughout the mission: 3.25 AU (Rosetta instruments on), 2.7 AU (Lander down), 2.0 AU, and 1.3 AU (perihelion). Because of the large range of gas production rates, we have used both a fluid-based(More)
Aeronomy is a description of the physics and chemistry of the upper atmospheres and ionospheres of planetary bodies. In this chapter we consider those processes occurring R.E. Johnson ( ) Engineering Physics, University of Virginia, Charlottesville, VA 22904, USA e-mail: rej@virginia.edu R.E. Johnson Physics Department, New York University, 4 Washington(More)
[1] Presented in this paper are the results of a time-dependent, fully three-dimensional self-consistent ideal magneto-hydrodynamics (MHD) model of disconnection events (DEs) in the cometary plasma tail. Understanding the interaction of cometary plasma with the solar wind is a very important problem in space plasma physics. This study focuses on the(More)
Molecular nitrogen (N2) is thought to have been the most abundant form of nitrogen in the protosolar nebula. It is the main N-bearing molecule in the atmospheres of Pluto and Triton and probably the main nitrogen reservoir from which the giant planets formed. Yet in comets, often considered the most primitive bodies in the solar system, N2 has not been(More)
[1] The global dynamics of the flow of energetic particles through the Martian upper atmosphere is studied for different cases reflecting variations in solar cycle, seasons, and epochs over history. In this study, the combination of the new 3-D Direct Simulation Monte Carlo kinetic model and the modern 3-D Mars Thermosphere General Circulation Model is(More)
The importance of comets for the origin of life on Earth has been advocated for many decades. Amino acids are key ingredients in chemistry, leading to life as we know it. Many primitive meteorites contain amino acids, and it is generally believed that these are formed by aqueous alterations. In the collector aerogel and foil samples of the Stardust mission(More)
The SWAN (Solar Wind ANisotropies) Lyman-alpha all-sky camera on the SOHO spacecraft observed the hydrogen coma of comet C/1999 S4 (LINEAR) from the end of May through mid-August 2000. A systematic set of water-production rates was obtained for this well-documented event of complete fragmentation of a cometary nucleus. The observations indicate that the(More)
The origin of cometary matter and the potential contribution of comets to inner-planet atmospheres are long-standing problems. During a series of dedicated low-altitude orbits, the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) on the Rosetta spacecraft analyzed the isotopes of xenon in the coma of comet 67P/Churyumov-Gerasimenko. The(More)