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1970-2010: The Golden Age of Solar System Exploration

1970-2010: The Golden Age of Solar System Exploration. TNOs: Four decades of observations. F . Merlin M.A. Barucci S. Fornasier D. Perna. The discovery of the minor icy bodies in the solar system. The key dates: - First discovery of a Centaur: 1977 (Chiron by C.Kowal )

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1970-2010: The Golden Age of Solar System Exploration

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  1. 1970-2010: The Golden Age of Solar System Exploration TNOs: Four decades of observations. F. Merlin M.A. Barucci S. Fornasier D. Perna

  2. The discovery of the minor icy bodies in the solar system The key dates: - First discovery of a Centaur: 1977 (Chiron by C.Kowal) - First discovery of cometary like activity: 1988 (Chiron by D.Tholen) - First discovery of a TNO : 1992 (1992 QB1 by D.Jewitt) - First discovery of a binary object : 2001 (1998 WW31 by C.Veillet) - First discovery of a family object: 2006 (Haumea family by K.Barkume) F. Merlin

  3. The different dynamical groups of TNOs and the Centaurs Need to classify the thousands of objects: - Withactual orbital elements +Study of the orbital stability over 10 m.y. (Gladman et al. 2008) If yes... 1) Member of a resonance? -> Resonants 2) Tj<3.05 and q<7.38 A.U.? -> Comets 3) a<aN ? --> Centaurs 4) a>2000 ? --> Inner Oort cloud 5) Scatters ? --> Scattered 6) e > 0.24 ? --> Detached 7) 39.4 < a < 47.8 ? Main Classical Belt F. Merlin

  4. The four taxonomical classes, first evidence of variegated surface Among the TNOs and Centaurs, visible and near infrared colors show a quasi continuous trend Barucciet al. 2005 Barucci et al. 2011 Presence of icy compounds on all BB members, possible observational bias? IR members seem to be depleted of ices. The bimodality of the Centaurs cannot be explained from the icy content of their surface.

  5. Are there any links between dynamic and taxonomy? • BR bi-modality of the Centaurs: • Due to evolutionprocesses? • - Cometarylikeactivity: Possible • - No disruptive impacts. Unprobableduring the Centaur life • Seems to be the case for the small TNOs • If similar causes, we can exclude cometary activity • Cold and hot classical populations • Very red with e<0.05 and i<5° • The atmosphereless bodies are mainly • governed by the space weathering. • No disruptive collisions (collisions should occur with small velocities) should occurred and have greater effects on small bodies • - compatible with dynamical models from Dell’Oro and Davies&Farinella Peixinho et al. 2012

  6. Remote laboratory to investigate the effect of space weathering The bigpicture Irradiation acts on everyatmosphereless bodies. - destroy or modify the icy content of the surface  Dark or and redcrust Refreshmentprocessesact in differentways on the differentobjects - Icy compounds are revealed  Cometaryactivityresplenishes the whole surface (Centaurs)  Thinatmosphereredeposit (BigTNOswith volatile)  Collisions excavateinternal compounds (all TNOs and Centaurs) Jewitt

  7. Clues for strong evolution of the surface • Irradiation of thinsample : • Reddens the visible reflectance • Removes the absorption bands • Generates new absorbtion bands • Reduces the visible albedo • This explains the observation of dark, red and featurelessobjects. In details, canconstrain the initial composition Brunetto et al. 2006 • Population of objectscovered by methanol. • - Centaur, Resonant and classic - • CH3OH isassumed to be primordial • CH3OH mightbedestroyed by radiolysis • Refreshmentprocesses in the last Gy. • Possible cometarylikeactivity for Centaurs • Probable collisions for the TNOs Merlin et al. 2012

  8. Unveiling the physical and chemical properties of the surface Needhighqualityspectroscopy to retrieve: Chemical composition, using absorption bands of icy compounds and spectral models. Detection of C2H6 on Pluto in addition to N2, CO and CH4. Detection of ammonia hydrates on Chiron Detection of methanol on Pholusand on 2002 VE95. Spectral modellingusing a widewavelength range is able to giveconstraints on the particle size. Here, the case of Plutowithsub mm and cm size particles. Merlin et al. 2010

  9. Unveiling the physical and chemical properties of the surface Needhighqualityspectroscopy to retrieve: The surface temperaturecanberetrievedfrom the peak position of one or severalabsrption bands. From the peak position of the 1.65µm band of crystalline water ice (Merlin et al. 2006). From the peak position of several CH4 absortption band (Grundy et al. 2002). Spectral modelscanbeused for icy mixtures. Merlin et al. 2006 The dilution stateof the icescanbeestimatedfrom the position of several absorption bands too. CH4, CO, C2H6 in N2 for Pluto CH4 on N2 for Eris NH3 hydrates for Charon, Orcus  Needaccuratelaboratoryanalogs to disentanglebetweentemperature and dilution Merlin et al. 2010

  10. New Horizons, the future of TNOs exploration Departure Date: January 19th 2006 Arrival date at Pluto system: July 14th 2015 Instruments: Imager, spectrometer (UV, VIS, nIR) Spectral resolution: 2 angstroms (UV) up to 500 (nIR~2.20μm) NASA NASA-ESA Map the CO, CH4 and N2 species (temperature, dilution, abundancies, depth) Investigate the closestenvironment of Pluto (5 satellites) Followhis route toward possible new target…

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