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Arizonans Part of NASA Plan to Probe Pluto

Posted on: Saturday, 26 February 2005, 09:00 CST

Seventy-five years after Pluto was discovered at an Arizona observatory, planetary scientists are building on the work in Tucson and elsewhere - and some are on a team that will send a mission to the ninth planet as early as next year.

"The key to Pluto is that it unlocked the world of part of the outermost solar system," said astronomer David Levy of Vail, southeast of Tucson, who penned a book about Clyde Tombaugh, who discovered Pluto from Flagstaff's Lowell Observatory, and who is a frequent contributor to popular science journals. "Before 1930, we had no idea what the solar system was like beyond Neptune."

These days, planetary scientists at the University of Arizona, the Tucson-based nonprofit Planetary Science Institute and elsewhere examine the region in space they say was first opened up by Tombaugh's long-ago find.

Levy calls Pluto, at 3 billion miles from the sun, the "king of the Kuiper Belt" because it is found near a swath of space beyond Neptune that's teeming with smaller rock and ice objects like asteroids. The discovery of Pluto opened the door to Levy's finding several comets, many of which originate in the Kuiper Belt.

They include Halley's Comet and Shoemaker-Levy 9, Levy's namesake, which collided with Jupiter in 1994.

"The Kuiper Belt is so important because it actually consists of things that were used in the building of planets, unchanged since the formation of our solar system," Levy said. "If we can study those things, we can learn about our own past."

And that's exactly the aim of NASA in its New Horizons mission, which could launch as early as next January and reach the ninth planet by 2015. The mission was nearly scrapped several years ago when NASA re-evaluated its programs, but has since been salvaged.

Will Grundy, a planetary scientist at Lowell Observatory, has been using infrared imaging techniques to begin to tease out the materials that make up the distant planet. Within the past several years, he has discovered a patch rich in carbon monoxide on one side of the planet, and an area rich in methane ice on the other. When the New Horizons mission was still in the planning stages, he helped choose which instruments to send.

There has been debate about whether Pluto is a planet, but most serious planetary researchers don't dispute it, said Mark Sykes, director of Tucson's Planetary Science Institute. Sykes said Tombaugh originally believed Pluto was larger than it's known to be today - about 1,400 miles across - and for a while, each time astronomers took a closer look, the estimate shrunk.

He said it became a cocktail party joke that "at the rate it's going, Pluto is going to disappear or turn into an asteroid or something," and that's how its disputed status as a planet arose.

Sykes argues that Pluto has many things in common with the other known planets in the solar system: an atmosphere, seasons, a rocky core and an icy shell, along with a moon that was formed because of an impact, like Earth's.

He said it's likely that further exploration of the Kuiper Belt beyond Pluto will reveal that our solar system is larger than we thought, not smaller.

2 celebrations honor discovery

Clyde Tombaugh, who lived from 1906 to 1997, identified the ninth planet on Feb. 18, 1930, from deep sky photographs he took at Lowell Observatory in Flagstaff.

Tombaugh went on to start the astronomy program at New Mexico State University in Las Cruces. Celebrations to commemorate the anniversary of Pluto's discovery will take place Friday in Flagstaff and Saturday in Las Cruces.

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On the Net:

New Horizons Mission

* Contact reporter Anne Minard at 434-4086 or aminard@azstarnet.com.

Source: Arizona Daily Star

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