Atmosphere of Pluto from New Horizons Yuk Ling

Atmosphere of Pluto from New Horizons Yuk Ling Yung In collaboration with Mike Wong, Peter Gao, Josh Kammer, Randy Gladstone Mike Summers and Danie Liang + NH Team Caltech(GPS) + JPL (322) 23 June 2016

New Horizons First Mission to the Last Planet First Mission to the First Ex-Planet Pluto = Kuiper Belt Object

Launch 19 Jan 2006 Flyby 14 July 2015

NH Alice UV Spectrograph Bandpass: 52 -187 nm Filled-Slit Spectral Resolution: 0. 9 nm Spatial Resolution: 0. 3 /pixel 45 cm Field of View: 4º× 0. 1º (airglow) 2º× 2º (solar occultation) Effective Area: 0. 2 cm 2 @ 130 nm

Altitude, km • The REX uplink radio occultation results show a surface pressure of 11 µbars at ingress and 10 µbars at egress • The lowest 4 km at ingress are close to the solid-vapor equilibrium temperature of N 2 at Pluto’s surface pressure

Ingress & Egress Locations

Alice Pocc Total Count Rates N 2 opacity begins at z~1300 km chord/2 =1175 12 km (consistent with observed radius) CH 4 opacity begins at z~800 km Kink due to CH 4 (methane opacity all used up) Very symmetric uniform over planet C 2 HX opacity begins at z~250 km

Pluto’s FUV Opacity • Transmission based on Krasnopolsky & Cruikshank [1999] model

Pluto’s FUV Opacity • Transmission from Alice solar occultation data – where’s the N 2

Hazes

Pluto’s N 2 Opacity High-resolution solar spectrum from SOHO/SUMER High-resolution N 2 cross sections from Lewis & Heays, ANU • Zoom in on 97 -98 nm range to see how two bright solar lines are transmitted; Lyγ 97. 2 should be absorbed by N 2, CIII 97. 7 by CH 4

Movie

OUTLINE 1. Kuiper Belt Object (KBO) 2. New Horizons Mission 3. Atmosphere of Titan 4. Atmosphere of Pluto

Comprehensive Chemical Model: KINETICS • 1200 Species • 20, 000 reactions • Coupled to aerosol microphysics Mark Allen Run-Lie Shia • Coupled to 1 -D and 2 -D transport • Applied to Solar System Planets, Earth as a Planet, Exoplanets and Planetary Evolution • More than 300 refereed publications • Allen et al. (1981), Shia, Morgan, Weibel, Willacy + Students

Strobel 1969, 1973 Gladstone et al. 1996 Moses et al. 2005

Yung et al. 1984 Li et al. 2014, 2015 Vuitton et al. 2007, 2008

Titan is Nature’s laboratory for organic synthesis, fulfilling the vision of Urey and Miller (1953) However, the emergence of life requires more than that.

Tholins on Titan Data: Cassini UVIS Liang et al. 2007 Kammer et al. 2015 Lavvas et al. 2013

Xi (Arthur) Zhang et al. 2013 Horst et al. 2012 Trainer et al. 2006

OUTLINE 1. Kuiper Belt Object (KBO) 2. New Horizons Mission 3. Atmosphere of Titan 4. Atmosphere of Pluto

Acknowledgements Yung’s group at Caltech, Mark Allen, Michael Wong, Peter Gao, Run-Lie Shia, Xi Zhang, Siteng Fan, Josh Kammer, Randy Gladstone, Michael Summers, Leslie Young, NH Team

Ingress & Egress Locations