Organic materials in planetary and protoplanetary systems: nature or nurture?

¹ Centre International d’Ateliers Scientifiques de l’Observatoire de Paris Paris France
² SETI Institute, 189 Bernardo Ave., Mountain View, CA 94043, USA
e-mail: Cristina.M.DalleOre@nasa.gov
³ NASA Ames Research Center, Mail Stop 245-6, Moffett Field, CA 94035, USA
e-mail: Dale.P.Cruikshank@nasa.gov
⁴ LESIA, Observatoire de Paris, 92195 Meudon Principal Cedex, France
e-mail: marcello.fulchignoni@obspm.fr, Antonella.Barucci@obspm.fr, Catherine.deBergh@obspm.fr
⁵ Institute d’Astrophysique Spatiale (IAS), Université Paris 11 and CNRS, 91405 Orsay, France
⁶ Physics Department, University of Central Florida, Orlando, FL 32816, USA
⁷ NASA Postdoctoral Program Fellow, Goddard Space Flight Center, USA
⁸ INAF – Osservatorio Astronomico di Roma, via Frascati 33, 00040   Monteporzio Catone ( Roma), Italy
e-mail: Dotto@mporzio.astro.it
⁹ Earth and Planetary Sciences Dept, University of Tennessee, Knoxville, TN 37919, USA
e-mail: JEmery2@utk.edu
¹⁰ Lowell Observatory, 1400 W.Mars Hill Rd., Flagstaff AZ 86001, USA
e-mail: W.Grundy@lowell.edu
¹¹ INAF Osservatorio Astronomico di Capodimonte, via Moiariello, 16, 80131 Napoli, Italy
¹² UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, Grenoble 38041, France
¹³ University of Hawaii, Institute for Astronomy, USA
e-mail: owen@ifa.hawaii.edu
¹⁴ Space Telescope Science Institute, Baltimore, MD 21218, USA
¹⁵ Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA
e-mail: Pascucci@stsci.edu
¹⁶ NASA Lunar Science Institute, Mail Stop 17-1, Moffett Field, CA 94035, USA
¹⁷ Nasa Postdoctoral Program, NASA Ames Research Center, Moffett Field, CA 94035, USA
e-mail: noemi.pinilla-alonso@nasa.gov
¹⁸ INAF – Osservatorio Astrofisico di Catania, via S. Sofia 78, 95123 Catania, Italy
e-mail: Gianni@oact.inaf.it

Received: 27 January 2011
Accepted: 6 June 2011

Abstract

Aims. The objective of this work is to summarize the discussion of a workshop aimed at investigating the properties, origins, and evolution of the materials that are responsible for the red coloration of the small objects in the outer parts of the solar system. Because of limitations or inconsistencies in the observations and, until recently, the limited availability of laboratory data, there are still many questions on the subject. Our goal is to approach two of the main questions in a systematic way:

– Is coloring an original signature of materials that are presolar in origin (“nature”) or stems from post-formational chemical alteration, or  weathering  (“nurture”)?

– What is the chemical signature of the material that causes spectra to be sloped towards the red in the visible?

We examine evidence available both from the laboratory and from observations sampling different parts of the solar system and circumstellar regions (disks).

Methods. We present a compilation of brief summaries gathered during the workshop and describe the evidence towards a primordial vs. evolutionary origin for the material that reddens the small objects in the outer parts of our, as well as in other, planetary systems. We proceed by first summarizing laboratory results followed by observational data collected at various distances from the Sun.

Results. While laboratory experiments show clear evidence of irradiation effects, particularly from ion bombardment, the first obstacle often resides in the ability to unequivocally identify the organic material in the observations. The lack of extended spectral data of good quality and resolution is at the base of this problem. Furthermore, that both mechanisms, weathering and presolar, act on the icy materials in a spectroscopically indistinguishable way makes our goal of defining the impact of each mechanism challenging.

Conclusions. Through a review of some of the workshop presentations and discussions, encompassing laboratory experiments as well as observational data, we infer that both “nature” and “nurture” are instrumental in the coloration of small objects in the outer parts