Pluto: the next decade of discovery Leslie Young Southwest Research Institute
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.
, distance increases by 6%, insolation decreases by 12%. Simplest models have temperature decreasing by 3% (~1.2K),for the pressure nearly halving.
Sicardy et al. 2003, Nature 424 Elliot et al. 2003, Nature 424
perihelion Hansen and Paige fig 3 (high thermal inertia) Hansen and Paige 1996, Icarus year
Hansen and Paige fig 4 (moderate thermal inertia) perihelion year
Hansen and Paige fig 7 (low thermal inertia) perihelion year
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight
II. Distinguishing seasonal models with observations
Changes in lightcurve mean and amplitude can be due to volatile transport or changing viewing. Stern et al. 1988, Icarus 75 Buie et al. 1997, Icarus /
Douté et al 1999, Icarus 142 N2N2 CH 4 CO 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 µm range includes N 2, CH 4, and CO. Shorter wavelengths include weak CH 4 bands, and CH4 and tholins have absorption at 3.3 µm (See Olkin 55.02).
year N 2 frost temperature 60 µm brightness temperature 1300 µm brightess temperature Hansen and Paige 1996, Icarus 120
Occultations are the most sensitive and direct measure of changes in atmospheric pressure. Young 2004, BAAS
2005 Jul 11 03:36:14 UT C313.2 (Sicardy 49.05, Young 55.04, Gulbis 55.05) 2006 Jun 12 16:21:49 UT P Oct 31 2:30:29 UT P May 12 4:42:24 UT P456
III. Some words of warning...
Young et al. 2001, AJ 121 Grundy & Buie 2001, Icarus 153 Young 55.03, Buie Non-secular time-dependent effects on visible albedo—rotation and possible opposition surges
Longitudinal change is much larger than the tentative secular variation (green vs. red dots) in CH µm band Grundy and Buie 2001,Icarus
Lellouch et al. 2000, Icarus 147 Thermal rotational lightcurves have higher amplitudes than the expected seasonal change..2 Jy.6 Jy.3 Jy 0 Jy.8 Jy.3 Jy.8 Jy
IV. New Horizons spacecraft to Pluto; flight
PERSI Remote Sensing Package Objectives: MVIC: Global geology and geomorphology. Stereo and terminator images. Refine radii and orbits. Search for rings and satellites. Search for clouds and hazes. LEISA: Global composition maps, high resolution composition maps, temperatures from NIR bands. ALICE: UV airglow and solar occultation to characterize Pluto’s neutral atmosphere. Search for ionosphere, H, H 2, and C x H y. Search for Charon’s atmosphere.
REX Radio Experiment Objectives: Profiles of number density, temperature, and pressure in Pluto ’s atmosphere, including conditions at surface. Search for Pluto’s ionosphere. Search for atmosphere and ionosphere on Charon. Measure masses and radii of Pluto and Charon, and masses of flyby KBOs. Measure disk- averaged microwave brightness temperatures (4.2 cm) of Pluto and Charon.
SWAP Solar Wind Plasma Sensor Objectives: Slowdown of the solar wind,as a diagnostic of Pluto’s atmospheric escape rate. Solar wind standoff Solar wind speed Solar wind density Nature of interaction of solar wind and Pluto’s atmosphere (distinguish magnetic, cometary, and ionospheric interactions)
PEPSSI Pluto Energetic Particle Spectrometer Objectives: Measure energetic particles from Pluto’s upper atmosphere,as a diagnostic of Pluto’s atmospheric escape rate.
LORRI Long Range Reconnasance Imager Objectives Far-side maps High-resolution closest approach images, including terminator and stereo imaging.
Summary We expect Pluto to undergo seasonal change in the next decade Observations can constrain models of voalatile transport in the outer solar system Beware spatial-temporal confusion! Long time-base observations support and are supported by the planned New Horizons mission to Pluto