14 DAY TRIAL // Coordinated observations of the collision of NASA's Deep Impact mission with comet 9P/Tempel 1 by the Subaru, Gemini and Keck telescopes on Mauna Kea delivered surprising new insights into the ancestry and life-cycles of comets. Specifically, materials beneath the comet's dusty skin shows striking similarities between two families of comets where no relationship had been suspected.
When NASA's Deep Impact mission ploughed into comet 9P/Tempel 1 on July 4th of this year, the giant telescopes on Mauna Kea had a unique view of the massive cloud of dust, gas and ice expelled during the collision. The observations also allowed scientists to determine the mass of material blasted out by the collision, which is estimated to be as much as 25 fully-loaded tractor trailer-trucks.
The findings are based on the composition of rocky dust detected by both the Subaru and Gemini 8-meter telescopes and ethane, water and carbon-based organic compounds revealed by the 10-meter W.M. Keck Observatory. The results from these Mauna Kea observations were made available today in a special segment in the journal Science highlighting results from the Deep Impact experiment.
The Deep Impact mission was designed to dig deep beneath this crusty exterior to learn more about the true nature of the comet's dust and ice components. "This comet definitely had something to hide under its veneer of rock and ice and we were ready with the world's biggest telescopes to find out what it was," said Chick Woodward of the University of Minneapolis and part of the Gemini observing team.
The combined observations show a complex mix of silicates, water and organic compounds beneath the surface of the comet. These materials are similar to what is seen in another class of comets thought to reside in a distant swarm of pristine bodies called the Oort Cloud. Oort Cloud comets are well preserved fossils in the frozen suburbs of the solar system that have changed little over the billions of years since their formation. When they are occasionally nudged gravitationally toward the Sun they warm up and release a profuse amount of gas and dust on a one-time visit to the inner solar system.
Returning comets like Tempel 1 (known as periodic comets) were believed to have formed in a colder nursery distinctly different from the birthplaces of their cousins, the Oort Cloud comets. The evidence for two distinct "family trees" lies in their vastly different orbits and apparent composition. "Now we see that the difference may really be just superficial: only skin deep." said Woodward. "Under the surface, these comets may not be so different after all.