[meteorite-list] New Hubble Images Show Similar Colors for Pluto's Moons

[Ron Baalke]

The Johns Hopkins University Applied Physics Laboratory
Office of Communications and Public Affairs
Laurel, Maryland

Media Contact: Michael Buckley
(443) 778-7536 or (240) 228-7536
michael.buckley at jhuapl.edu

March 10, 2006

FOR IMMEDIATE RELEASE

Note to Editors: Images to support this release are available at: 
http://hubblesite.org/newscenter/newsdesk/archive/releases/2006/15/image/

NEW HUBBLE IMAGES SHOW SIMILAR COLORS FOR PLUTO'S MOONS

Finding Supports Theory that Single Collision Created Ninth Planet's Three 
Satellites

Using new Hubble Space Telescope observations, a research team led by Dr. 
Hal Weaver of the Johns Hopkins University Applied Physics Laboratory and 
Dr. Alan Stern of the Southwest Research Institute has found that Pluto's 
three moons are essentially the same color - boosting the theory that the 
Pluto system formed in a single, giant collision.

Publishing their findings in an International Astronomical Union Circular 
(No. 8686), the team determined that Pluto's two "new" satellites, 
discovered in May 2005 and provisionally called S/2005 P 1 and S/2005 P 2, 
have identical colors to one another and are essentially the same, neutral 
color as Charon, Pluto's large moon discovered in 1978.

All three satellites have surfaces that reflect sunlight with equal 
efficiency at all wavelengths, which means they have the same color as the 
Sun or Earth's moon. In contrast, Pluto has more of a reddish hue.

The new observations were obtained March 2 with the high-resolution channel 
of the Hubble's Advanced Camera for Surveys. The team determined the 
bodies' colors by comparing the brightness of Pluto and each moon in images 
taken through a blue filter with those taken through a green/red filter. 
(The images are available on the Hubble Web site at 
http://hubblesite.org/newscenter/newsdesk/archive/releases/2006/15/image/)

"The high quality of the new data leaves little doubt that the hemispheres 
of P1 and P2 that we observed have essentially identical, neutral colors," 
says Weaver.

The new results further strengthen the hypothesis that Pluto and its 
satellites formed after a collision between two Pluto-sized objects nearly 
4.6 billion years ago. "Everything now makes even more sense," says Stern. 
"If all three satellites presumably formed from the same material lofted 
into orbit around Pluto from a giant impact, you might well expect the 
surfaces of all three satellites to have similar colors."

The researchers hope to make additional Hubble color observations, in 
several more filters, to see if the similarity among the satellites 
persists to longer (redder) wavelengths. They have proposed to obtain 
compositional information on the new satellites by observing them at 
near-infrared wavelengths, where various ice and mineral absorptions are 
located. The researchers also hope to better refine the orbits of P1 and P2 
and measure the moons' shapes and rotational periods.

The Hubble observations were made in support of NASA's New Horizons mission 
to Pluto and the Kuiper Belt. New Horizons launched on Jan. 19, 2006, and 
will fly through the Pluto system in July 2015, providing the first 
close-up look at the ninth planet and its moons. Stern leads the mission 
and science team as principal investigator; Weaver serves as the mission's 
project scientist. The Johns Hopkins University Applied Physics Laboratory, 
Laurel, Md., manages the mission for NASA's Science Mission Directorate and 
operates the New Horizons spacecraft. For more information on the mission, 
visit http://pluto.jhuapl.edu.

The other members of the Hubble Space Telescope-Pluto satellite observing 
team include Max Mutchler of the Space Telescope Science Institute, 
Baltimore; Drs. William Merline, John Spencer, Andrew Steffl, Elliot Young 
and Leslie Young of Southwest Research Institute, Boulder, Colo.; and Dr. 
Marc Buie of Lowell Observatory, Flagstaff, Ariz.

The IAU Circular is available at 
http://cfa-www.harvard.edu/iau/special/08686.pdf
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