Pluto: the next decade of discovery. Leslie Young Southwest Research Institute [email protected] I. Decade-scale surface-atmosphere interaction. 2005: 30.9 AU, 34° sub-solar lat 2015: 32.8 AU, 49° sub-solar lat Farther at 0.2 AU/year distance, More northerly at 1.5 °/year.
2015: 32.8 AU, 49° sub-solar lat
Farther at 0.2 AU/year distance,
More northerly at 1.5 °/year.
2005-2015, distance increases by 6%, insolation decreases by 12%. Simplest models have temperature decreasing by 3% (~1.2K),for the pressure nearly halving.
Elliot et al. 2003, Nature 424
Hansen and Paige 1996, Icarus 120
Stern et al. 1988, Icarus 75
Buie et al. 1997, Icarus 125
Changes in lightcurve mean and amplitude can be due to volatile transport or changing viewing.
Spectra on the surface absorption in reflected sunlight is diagnostic of the volatiles on Pluto\'s surface, including their grain size, mixing state, and temperature. 0.8-2.5 µm range includes N2, CH4, and CO. Shorter wavelengths include weak CH4 bands, and CH4 and tholins have absorption at 3.3 µm (See Olkin 55.02).
1300 µm brightess temperature
60 µm brightness temperature
N2 frost temperature
Occultations are the most sensitive and direct measure of changes in atmospheric pressure.
Young 55.03, Buie 49.03
Young et al. 2001, AJ 121
Non-secular time-dependent effects on visible
albedo—rotation and possible opposition surges
Grundy and Buie 2001,Icarus 153.
Longitudinal change is much larger than the tentative secular variation (green vs. red dots) in CH4 1.66 µm band
Thermal rotational lightcurves have higher amplitudes thanthe expected seasonal change.
• Far-side maps
• High-resolution closest approach images, including terminator and stereo imaging.