[meteorite-list] Pluto and Charon: New Horizons' Dynamic Duo

[Ron Baalke]

http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20150709

Pluto and Charon: New Horizons' Dynamic Duo
July 9, 2015

[Image]
New Horizons was about 3.7 million miles (6 million kilometers) from Pluto 
and Charon when it snapped this portrait late on July 8, 2015. Most of 
the bright features around Pluto's edge are a result of image processing, 
but the bright sliver below the dark "whale," which is also visible in 
unprocessed images, is real.

This is the same image of Pluto and Charon from July 8, 2015; color information 
obtained earlier in the mission from the Ralph instrument has been added.

[Image]
Image of Pluto only from the New Horizons' Long Range Reconnaissance Imager 
(LORRI), July 8, 2015. Most of the bright features around Pluto's edge 
are a result of image processing, but the bright sliver below the dark 
"whale," which is also visible in unprocessed images, is real.

[Image] 
Image of Charon only from the New Horizons' Long Range Reconnaissance 
Imager (LORRI), July 8, 2015.

They're a fascinating pair: Two icy worlds, spinning around their common 
center of gravity like a pair of figure skaters clasping hands. Scientists 
believe they were shaped by a cosmic collision billions of years ago, 
and yet, in many ways, they seem more like strangers than siblings.

A high-contrast array of bright and dark features covers Pluto's surface, 
while on Charon, only a dark polar region interrupts a generally more 
uniform light gray terrain. The reddish materials that color Pluto are 
absent on Charon. Pluto has a significant atmosphere; Charon does not. 
On Pluto, exotic ices like frozen nitrogen, methane, and carbon monoxide 
have been found, while Charon's surface is made of frozen water and ammonia 
compounds. The interior of Pluto is mostly rock, while Charon contains 
equal measures of rock and water ice.

"These two objects have been together for billions of years, in the same 
orbit, but they are totally different," said Principal Investigator Alan 
Stern of the Southwest Research Institute (SwRI), Boulder,  Colorado.

Charon is about 750 miles (1200 kilometers) across, about half the diameter 
of Pluto - making it the solar system's largest moon relative to its planet. 
Its smaller size and lower surface contrast have made it harder for New 
Horizons to capture its surface features from afar, but the latest, closer 
images of Charon's surface show intriguing fine details.

Newly revealed are brighter areas on Charon that members of the mission's 
Geology, Geophysics and Imaging team (GGI) suspect might be impact craters. 
If so, the scientists would put them to good use. "If we see impact craters 
on Charon, it will help us see what's hidden beneath the surface," said 
GGI leader Jeff Moore of NASA's Ames Research Center. "Large craters can 
excavate material from several miles down and reveal the composition of 
the interior."

In short, said GGI deputy team leader John Spencer of SwRI, "Charon is 
now emerging as its own world. Its personality is beginning to really 
reveal itself."