[meteorite-list] New Horizons Captures Two of Pluto's Smaller Moons

[Ron Baalke]

http://www.nasa.gov/image-feature/new-horizons-captures-two-of-plutos-smaller-moons

New Horizons Captures Two of Pluto's Smaller Moons
July 21, 2015

[Image]
Pluto's moon Nix (left), shown here in enhanced color as imaged by the 
New Horizons Ralph instrument, has a reddish spot that has attracted the 
interest of mission scientists.  The data were obtained on the morning 
of July 14, 2015, and received on the ground on July 18.  At the time 
the observations were taken New Horizons was about 102,000 miles (165,000 
km) from Nix. The image shows features as small as approximately 2 miles 
(3 kilometers) across on Nix, which is estimated to be 26 miles (42 kilometers) 
long and 22 miles (36 kilometers) wide.

Pluto's small, irregularly shaped moon Hydra (right) is revealed in this 
black and white image taken from New Horizons' LORRI instrument on July 
14, 2015, from a distance of about 143,000 miles (231,000 kilometers). 
Features as small as 0.7 miles (1.2 kilometers) are visible on Hydra, 
which measures 34 miles (55 kilometers) in length. 

While Pluto's largest moon Charon has grabbed most of the lunar spotlight 
so far, these two smaller and lesser-known satellites are now getting 
some attention.  Nix and Hydra - the second and third moons to be discovered 
- are approximately the same size, but their similarity ends there.

New Horizons' first color image of Pluto's moon Nix, in which colors have 
been enhanced, reveals an intriguing  region on the jelly bean-shaped 
satellite, which is estimated to be 26 miles (42 kilometers) long and 
22 miles (36 kilometers) wide.

Although the overall surface color of Nix is neutral grey in the image, 
the newfound region has a distinct red tint.  Hints of a bull's-eye pattern 
lead scientists to speculate that the reddish region is a crater. "Additional 
compositional data has already been taken of Nix, but is not yet downlinked. 
It will tell us why this region is redder than its surroundings," said 
mission scientist Carly Howett, Southwest Research Institute, Boulder, 
Colorado. She added, "This observation is so tantalizing, I'm finding 
it hard to be patient for more Nix data to be downlinked."  

Meanwhile, the sharpest image yet received from New Horizons of Pluto's 
satellite Hydra shows that its irregular shape resembles the state of 
Michigan. The new image was made by the Long Range Reconnaissance Imager 
(LORRI) on July 14, 2015 from a distance of 143,000 miles (231,000 kilometers), 
and shows features as small as 0.7 miles (1.2 kilometers) across. There 
appear to be at least two large craters, one of which is mostly in shadow. 
The upper portion looks darker than the rest of Hydra, suggesting a possible 
difference in surface composition. From this image, mission scientists 
have estimated that Hydra is 34 miles (55 kilometers) long and 25 miles 
(40 kilometers) wide. Commented mission science collaborator Ted Stryk 
of Roane State Community College in Tennessee, "Before last week, Hydra 
was just a faint point of light, so it's a surreal experience to see it 
become an actual place, as we see its shape and spot recognizable features 
on its surface for the first time."

Images of Pluto's most recently discovered moons, Styx and Kerberos, are 
expected to be transmitted to Earth no later than mid-October.

Nix and Hydra were both discovered in 2005 using Hubble Space Telescope 
data by a research team led by New Horizons project scientist Hal Weaver, 
Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland. 
New Horizons' findings on the surface characteristics and other properties 
of Nix and Hydra will help scientists understand the origins and subsequent 
history of Pluto and its moons.

Image Credit: NASA/JHUAPL/SWRI