The formation of Charon's red poles from seasonally cold-trapped volatiles.
A unique feature of Pluto's large satellite Charon is its dark red northern polar cap. Similar colours on Pluto's surface have been attributed to tholin-like organic macromolecules produced by energetic radiation processing of hydrocarbons. The polar location on Charon implicates the temperature extremes that result from Charon's high obliquity and long seasons in the production of this material. The escape of Pluto's atmosphere provides a potential feedstock for a complex chemistry. Gas from Pluto that is transiently cold-trapped and processed at Charon's winter pole was proposed as an explanation for the dark coloration on the basis of an image of Charon's northern hemisphere, but not modelled quantitatively. Here we report images of the southern hemisphere illuminated by Pluto-shine and also images taken during the approach phase that show the northern polar cap over a range of longitudes. We model the surface thermal environment on Charon and the supply and temporary cold-trapping of material escaping from Pluto, as well as the photolytic processing of this material into more complex and less volatile molecules while cold-trapped. The model results are consistent with the proposed mechanism for producing the observed colour pattern on Charon.
Lowell Observatory, Flagstaff, Arizona, USA.
W M
WM
Grundy
NASA Ames Research Center, Moffett Field, California, USA.
D P
DP
Cruikshank
Southwest Research Institute, San Antonio, Texas, USA.
G R
GR
Gladstone
Southwest Research Institute, Boulder, Colorado, USA.
C J A
CJ
Howett
National Optical Astronomy Observatory, Tucson, Arizona, USA.
T R
TR
Lauer
Southwest Research Institute, Boulder, Colorado, USA.
J R
JR
Spencer
George Mason University, Fairfax, Virginia, USA.
M E
ME
Summers
Southwest Research Institute, Boulder, Colorado, USA.
M W
MW
Buie
Massachussetts Institute of Technology, Cambridge, Massachusetts, USA.
A M
AM
Earle
NASA Ames Research Center, Moffett Field, California, USA.
K
K
Ennico
Southwest Research Institute, Boulder, Colorado, USA.
J Wm
JW
Parker
Southwest Research Institute, Boulder, Colorado, USA.
S B
SB
Porter
Southwest Research Institute, Boulder, Colorado, USA.
K N
KN
Singer
Southwest Research Institute, Boulder, Colorado, USA.
S A
SA
Stern
University of Virginia, Charlotteville, Virginia, USA.
A J
AJ
Verbiscer
NASA Ames Research Center, Moffett Field, California, USA.|Carl Sagan Center, SETI Institute, Mountain View, California, USA.
R A
RA
Beyer
Massachussetts Institute of Technology, Cambridge, Massachusetts, USA.
R P
RP
Binzel
NASA Jet Propulsion Laboratory, La Cañada Flintridge, California, USA.
B J
BJ
Buratti
Southwest Research Institute, Boulder, Colorado, USA.
J C
JC
Cook
NASA Ames Research Center, Moffett Field, California, USA.|Carl Sagan Center, SETI Institute, Mountain View, California, USA.
C M
CM
Dalle Ore
Southwest Research Institute, Boulder, Colorado, USA.
C B
CB
Olkin
Southwest Research Institute, Boulder, Colorado, USA.
A H
AH
Parker
University of Maryland, College Park, Maryland, USA.
S
S
Protopapa
Université Grenoble Alpes, CNRS, IPAG, Grenoble, France.
E
E
Quirico
Southwest Research Institute, San Antonio, Texas, USA.
K D
KD
Retherford
Southwest Research Institute, Boulder, Colorado, USA.
S J
SJ
Robbins
Université Grenoble Alpes, CNRS, IPAG, Grenoble, France.
B
B
Schmitt
Space Telescope Science Institute, Baltimore, Maryland, USA.
J A
JA
Stansberry
NASA Ames Research Center, Moffett Field, California, USA.
O M
OM
Umurhan
Johns Hopkins University Applied Physics Laboratory, Columbia, Maryland, USA.
H A
HA
Weaver
Southwest Research Institute, Boulder, Colorado, USA.
L A
LA
Young
Southwest Research Institute, Boulder, Colorado, USA.
A M
AM
Zangari
Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA.
V J
VJ
Bray
Johns Hopkins University Applied Physics Laboratory, Columbia, Maryland, USA.
A F
AF
Cheng
Washington University in St Louis, St Louis, Missouri, USA.
W B
WB
McKinnon
Johns Hopkins University Applied Physics Laboratory, Columbia, Maryland, USA.
R L
RL
McNutt
NASA Ames Research Center, Moffett Field, California, USA.
J M
JM
Moore
University of California, Santa Cruz, California, USA.
F
F
Nimmo
NASA Goddard Space Flight Center, Greenbelt, Maryland, USA.
D C
DC
Reuter
Lunar and Planetary Institute, Houston, Texas, USA.
P M
PM
Schenk