1. Pluto: the next decade of discovery Leslie Young Southwest Research Institute layoung@boulder.swri.edu

2. I. Decade-scale surface- atmosphere interaction

3. 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.

5. 2005-2015, distance increases by 6%, insolation decreases by 12%. Simplest models have temperature decreasing by 3% (~1.2K),for the pressure nearly halving.

6. Sicardy et al. 2003, Nature 424 Elliot et al. 2003, Nature 424

7. perihelion Hansen and Paige fig 3 (high thermal inertia) Hansen and Paige 1996, Icarus 120 10001200year

8. Hansen and Paige fig 4 (moderate thermal inertia) perihelion 10001200year

9. Hansen and Paige fig 7 (low thermal inertia) perihelion 10001200year

10. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

11. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

12. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

13. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

14. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

15. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

16. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

17. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

18. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

19. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

20. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

21. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

22. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

23. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

24. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

25. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

26. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

27. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

28. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

29. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

30. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

31. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

32. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

33. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

34. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

35. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

36. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

37. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

38. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

39. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

40. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

41. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

42. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

43. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

44. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

45. Darkening of ices following sublimation Thermal inertia Old, frost-covered winter pole coming into sunlight

46. II. Distinguishing seasonal models with observations

47. 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 125 1992/93 1982. 2 1975.2 1964.4 1954.8

48. 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. 0.8-2.5 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).

49. 10001200year N 2 frost temperature 60 µm brightness temperature 1300 µm brightess temperature Hansen and Paige 1996, Icarus 120

50. Occultations are the most sensitive and direct measure of changes in atmospheric pressure. Young 2004, BAAS

52. 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 P384.2 2006 Oct 31 2:30:29 UT P415 2007 May 12 4:42:24 UT P456

53. III. Some words of warning...

54. Young et al. 2001, AJ 121 Grundy & Buie 2001, Icarus 153 Young 55.03, Buie 49.03 Non-secular time-dependent effects on visible albedo—rotation and possible opposition surges

55. Longitudinal change is much larger than the tentative secular variation (green vs. red dots) in CH4 1.66 µm band Grundy and Buie 2001,Icarus 153. 1995 1998

56. 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

57. IV. New Horizons spacecraft to Pluto; flight 2006-2015

60. 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.

61. 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.

62. 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)

63. PEPSSI Pluto Energetic Particle Spectrometer Objectives: Measure energetic particles from Pluto’s upper atmosphere,as a diagnostic of Pluto’s atmospheric escape rate.

64. LORRI Long Range Reconnasance Imager Objectives Far-side maps High-resolution closest approach images, including terminator and stereo imaging.

65. 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