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The D/H and ^18^O/^16^O ratios in water from comet P/Halley.

Eberhardt, P.; Krankowsky, D.; Hodges, R. R. +1 more

From a detailed evaluation of the ion currents measured by the Neutral Mass Spectrometer (NMS) on the Giotto spaceprobe in the 17.5amu/e to 21.5amu/e mass range inside the contact surface of P/Halley we derive the cometary ion densities for masses 18amu/e to 21amu/e. From these we calculate the deuterium and ^18^O abundances in the H_3_O^+^ ion to…

Gas and dust emission from a dusty porous comet.

Capaccioni, F.; Orosei, R.; Coradini, A. +5 more

A comet nucleus is a porous aggregate of ices and dust in which solar heating causes the sublimation of volatiles and the ejection of dust particles lifted by the flow of the escaping gases. We present a numerical model that solves the heat conduction and the gas diffusion equations throughout a porous comet nucleus made of H_2_O ice, CO_2_ ice an…

The electron temperature in the inner coma of comet P/Halley.

Eberhardt, P.; Krankowsky, D.

From the CH_3_OH_2_^+^/H_3_O^+^ and H_3_O^+^/H_2_O^+^ ratios measured by the Giotto Neutral Mass Spectrometer in the inner coma (distance <20000km) of comet P/Halley we derive two independent electron temperature profiles. They agree very well and the electron temperature T_e_ increases gradually from =~100K at 2000km to =~900K at 8500km follow…

The sensitivity of the size distribution to the grain dynamics: simulation of the dust flux measured by GIOTTO at P/Halley.

Fulle, M.; Mennella, V.; Colangeli, L. +2 more

A cometary dust emission model, based on rigorous keplerian dynamics, is developed and, for the first time, the dependence of fluence on the probability distribution of the dust ejection velocity vector is demonstrated. The results are compared with the fluences measured by the DIDSY experiment on board the GIOTTO spacecraft during the Halley's fl…

Physics and chemistry of ions in the pile-up region of comet P/Halley.

Altwegg, K.; Balsiger, H.; Geiss, J. +1 more

Measurements by the mass spectrometers onboard Giotto during the flyby at comet P/Halley showed a steep increase in the ion density outside the diamagnetic cavity at a distance of about 8000km from the nucleus (Balsiger et al. 1986a; Krankowsky et al. 1986). The maximum ion density was observed at a distance of 12000km from the nucleus rather than…