[meteorite-list] The Youngest Crater on Charon?

[Ron Baalke]

http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20151029b

The Youngest Crater on Charon?
New Horizons
October 29, 2015

[Image]
This composite image is based on observations from the New Horizons Ralph/LEISA 
instrument made at 10:25 UT (6:25 a.m. EDT) on July 14, 2015, when New 
Horizons was 50,000 miles (81,000 kilometers) from Charon. The spatial 
resolution is 3 miles (5 kilometers) per pixel. The LEISA data were downlinked 
Oct. 1-4, 2015, and processed into a map of Charon's 2.2 micron ammonia-ice 
absorption band. Long Range Reconnaissance Imager (LORRI) panchromatic 
images used as the background in this composite were taken about 8:33 
UT (4:33 a.m. EDT) July 14 at a resolution of 0.6 miles (0.9 kilometers) 
per pixel and downlinked Oct. 5-6. The ammonia absorption map from LEISA 
is shown in green on the LORRI image. The region covered by the yellow 
box is 174 miles across (280 kilometers).

New Horizons scientists have discovered a striking contrast between one 
of the fresh craters on Pluto's largest moon Charon and a neighboring 
crater dotting the moon's Pluto-facing hemisphere.

The crater, informally named Organa, caught scientists' attention as they 
were studying New Horizons' highest-resolution infrared compositional 
scan of Charon. Organa and portions of the surrounding material ejected 
from it show infrared absorption at wavelengths of about 2.2 microns, 
indicating that the crater is rich in frozen ammonia -- and, from what 
scientists have seen so far, unique on Pluto's largest moon. The infrared 
spectrum of nearby Skywalker crater, for example, is similar to the rest 
of Charon's craters and surface, with features dominated by ordinary water 
ice.

Using telescopes, scientists first observed ammonia absorption on Charon 
in 2000, but the concentrations of ammonia around this crater are unprecedented.