Changes in Triton Surprise
August 4, 2004
Unexpected Variation in Triton's Nitrogen Frost
Change happens quickly on Neptune's moon Triton, some observers report,
with its visible color changing from gray to red and back from one
year to another. To understand why, Leslie Young, Will Grundy, and
Eliot Young have been watching Triton since July 2002 in the
near-infrared, where the ices on Triton's surface absorb sunlight. We
began this stake-out with eight consecutive nights, a little longer
than Triton's 5.9 day period, to decouple changes in time from
longitudinal variation. This was supposed to be the boring part of
the project, establishing the "typical" Triton, but Triton wasn't
informed. Instead, the SwRI team and its collaborator Dr. Will Grundy at
Lowell Observatory in Flagstaff were surprised to find that the absorption
by nitrogen ice, the main ice on Triton's surface, was twice as deep on
the side that faces Neptune as on the opposite side. While many
satellites have leading/trailing asymmetry, this
sub-Neptune/anti-Neptune asymmetry was completely unexpected. One
explanation is that the nitrogen frost has been subliming from the
area around the sunlit south pole, leaving a nitrogen-rich equatorial
collar that is larger on the sub-Neptune than anti-Neptune side.
Full details can be found in Grundy, W. M. and Young, L. A. 2004.
Near-infrared spectral monitoring of Triton with IRTF/SpeX I:
Establishing a baseline for rotational variability. Icarus, in press.
[downloadable from http://www.boulder.swri.edu/~layoung]
Other Recent Results
