Jochen Kissel, Dust & Cometary Science,
Max Planck Institute for Solar System Research
When I was a child, my grandmother told me about the big comet of 1910 – Halley's Comet. After two big wars in Germany, she was the only surviving family member of that generation and she had many stories to tell me. As fascinating as her stories were, I remember looking in the night sky for a similarly big comet, to no avail. Growing interests in other things made me forget about comets.
But comets did not forget me.
After 12 years of schooling through elementary and high school, I began to study physics in college. I ended up earning a master’s degree in nuclear physics - still, no comets around. For my Ph.D., my focus shifted to atmospheric research, launching mass-spectrometers on rockets—a bit closer to studying comets - if they wouldn’t come to me, perhaps I could go to them! A new work opportunity arose for me in a group doing research on extraterrestrial dust. It is there that I learned space research with instruments on HEOS and HELIOS satellites. During this time my director, Hugo Fechtig, asked that everybody in the group present a paper on comets for a seminar we organized. I was fascinated by those relatively tiny bodies which develop into the largest phenomena in the solar system—a body a few km across makes a H-halo 1/3 of the Earth’s orbit around the Sun!
Since early days in my career, comets have captured the attention of space research. With the anticipated return of Halley’s Comet, the European Space Agency (ESA) started the GIOTTO mission. I had an instrument on it – the latest mass spectrometer of the time. The Soviets (as they were known then) wanted to redirect their VENUS missions to Halley's comet. This was another flight opportunity for my PIA instrument, now as PUMA (Russian for Particulate Impact Analyzer). In dedicated meetings in Sulden, a small Italian mountain community, my team and I prepared alongside an international group of scientists. We poured over every aspect they could possibly measure.
Launched in 1984 and 1985, three spacecraft flew by Halley's comet in 1986 with my instruments on board. This was the first in-situ analysis of cometary grains and produced fascinating results—complex volatile organic material next to very small mineral grains. My boyhood belief in the mystery of comets was confirmed—where else could you find such a mixture? It took years to interpret all aspects of the data delivered by those instruments.
Having missed the Halley opportunity, in 1986 NASA announced the CRAF mission. Instead of zipping by it at 70 kilometers per second as with Halley, CRAF was to rendezvous and fly with the comet for almost a year. Special instrumentation was necessary. Together with an international team, my group had developed TOF-SIMS (time-of-flight secondary-ion-mass-spectrometer), where the dust was collected and then analyzed by shooting primary ions on the sample and collecting the secondary ions released by the bombardment. While the Halley dust spectrometers had a mass resolution of about 150-200, this new instrument, CoMA (Cometary Matter Analyzer), could achieve a resolution of 20,000, enough to separate even very large organic molecules. Unfortunately, when the development was almost finished in 1992, NASA cancelled the mission. When my director retired at about the same time, it seemed like my time with comets had come to an end.