Pluto's atmosphere near perihelion

by: Trafton, L. M.

ABSTRACT

A recent stellar occultation has confirmed predictions that Pluto has an
atmosphere which is sufficiently thick to uniformly envelope the planet
and to extend far above the surface. Pluto's atmosphere consists of methane
and perhaps other volatile gases at temperatures below their freezing points
it should regulate the surface temperature of its volatile ices to a global-
ly uniform value. As Pluto approaches and passes through perihelion, a sea-
sonal maximum in the atmospheric bulk and a corresponding minimum in the
exposed volatile ice abundance is expected to occur. The lag in maximum
atmospheric bulk relative to perihelion will be diagnostic of the surface
thermal properties. An estimate of Pluto's atmospheric bulk may result if
a global darkening (resulting from the disappearance of the seasonally
deposited frosts) occurs before the time of maximum atmospheric bulk. The
ice deposited shortly after perihelion may be diagnostic of the composition
of Pluto's volatile reservoir.

Geophysical Research Letters, ISSN 0094-8276, vol. 16, Nov. 1989, p. 1213-
1216.