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The Honolulu Advertiser
Posted on: Sunday, April 8, 2001

Comets may be integral component of Earth

By Jan TenBruggencate
Advertiser Science Writer

Each of us may have a little bit of comet dust in us.

That's nothing special. It's just a result of living on a planet that may be part comet.

University of Hawai'i researchers are learning more about comets using NASA's infrared telescope atop Mauna Kea. The telescope goes by the acronym IRTF, for Infrared Telescope Facility.

The university has ran the telescope since it opened in 1979, and has just been granted a new $17 million, five-year contract to continue running it. The telescope runs on a budget of $3.2 million a year and employs 24 people, both at the University of Hawai'i-Manoa and at the Institute for Astronomy facility at the Hilo University Park.

Alan Tokunaga, University of Hawai'i infrared astronomer, said our planet, which seems so unified, may have been built out of smaller objects.

"We believe the Earth was formed from the accretion of planetesimals," or smaller bodies that inhabited the young solar system, he said.

Among those objects are comets, which are formed in the cold outer reaches of the solar system, beyond the orbit of Jupiter.

"Comets are primitive bodies in our solar system, which reflect the chemical composition of the early proto-solar nebula," said astronomer Rolf-Peter Kudritzki, director of the University of Hawai'i's Institute for Astronomy.

Comets are often described as dirty balls of ice, and they have large amounts of compounds crucial to the planet's ability to sustain life. They have both water and hydrocarbons. (Hydrocarbons are a class of chemicals that contain both carbon and hydrogen.)

The solar system is about 5 billion years old, Kudritzki said, and comets may be more than 4 billion years old.

Perhaps half the water on Earth was delivered aboard comets, Tokunaga said. The rest probably came with the rocky asteroid-like objects that helped build the rest of the Earth. Asteroids orbit much closer to the sun than comets, and tend to contain higher percentages of minerals like iron, having lost most of their more volatile compounds.

Astronomers from around the country apply for time on the telescope, about 50 percent of which is spent on work within our solar system, and the rest on studies outside its borders.

While the IRTF's mirror could function as a visible-light telescope, NASA and scientists like Tokunaga have emphasized building equipment to gather light at the infrared end of the spectrum.

Infrared viewing within the solar system gives a better picture of planetary and other small objects because the technique "sees" cooler objects that are not readily visible in visible light.

"Infrared radiation is particularly useful in measuring the temperature and composition of astronomical bodies, especially those obscured by the dust and gas in interstellar space," the Institute for Astronomy said in a press release.

Beyond the solar system, the IRTF is used to study distant galaxies, very young stars and brown dwarfs — the astronomy community's term for space objects that are larger than Jupiter but smaller than the smallest stars.

Within the solar system, the telescope sometimes is diverted to emergency tasks for NASA, like reporting on atmospheric conditions on Jupiter when the Galileo spacecraft's on-board antenna failed.