NASA Astrobiology Institute (NAI)

1. Module 2: Formation of Habitable Planetary Systems

   Project Investigators: Mark Giampapa, Renu Malhotra, Michael Meyer, Joan Najita

   Other Project Members

   Daniel Apai (Research Staff)

   Stephanie Cortes (Doctoral Student)

   Greg Doppmann (Research Staff)

   Illaria Pascucci (Research Staff)

   William Sherry (Research Staff)

   Dante Lauretta (Collaborator)

   Jade Bond (Doctoral Student)

   Alan Aversa (Undergraduate Student)

   Eric Craine (Collaborator)

   Roy Tucker (Collaborator)

   Summary

   Our goal is to understand the physical processes that lead to planet formation, with a focus on aspects that determine the suitability of those planets to harbor life. Our main tool to accomplish this goal is observational astronomy. We utilize a variety of ground- and space-based telescopes across the electro-magnetic spectrum to make observations of circumstellar disks around sun-like as a function of the age of each system in order to constrain theories of planet formation and evolution. A central aspect of this work is to understand chemical processes that occur in disks and how such processes determine the structure and composition of the planets formed from them.

   Astrobiology Roadmap Objectives:

   • Objective 1.1: Models of formation and evolution of habitable planets
   • Objective 1.2: Indirect and direct astronomical observations of extrasolar habitable planets
   • Objective 3.1: Sources of prebiotic materials and catalysts

   Project Progress

   Module 2: Formation of Habitable Planetary Systems

   Meyer and colleagues continue to use data from the Spitzer Space Telescope to study the formation and evolution of planetary systems. Recent highlights include using observations of warm dust to constrain theories of planet formation. Preliminary results suggest that the processes thought to have lead to the formation of terrestrial planets in our solar system could be very common around sun-like stars. Follow-up studies include: a) analysis of the disk chemistry using mid-infrared spectra from Spitzer (led by Ilaria Pascucci); b) deep sub-millimeter surveys for gas and dust (led by Arizona students Stephanie Cortes and Alan Aversa); and c) thermal IR search for planets thought to be the outcome of such processes (led by Daniel Apai). In collaboration with former student Eric Mamajek, Meyer investigated whether forming planets could be detected as hot proto-planet collision afterglows. The results could have implications for strategies to obtain the first images or terrestrial planets with ground- or space-based telescopes.

   Joan Najita and colleagues continues to develop the tools for studying the gas in the planet formation region of disks. With John Carr, she reported the detection of organic molecules and water in typical T Tauri disks using high resolution Spitzer spectroscopy in the journal Science. With Al Glassgold and Rowin Meijerink, she has been enhancing disk chemistry models to understand the disk physical and chemical conditions that are needed to produce such emission. Carr and Najita have also been using high resolution IR spectroscopy of CO fundamental emission to study the gas content and distribution in T Tauri disks. In a recent paper, they report that the CO emission in one transition object is radially truncated and lay out the possible interpretations, including the presence of an orbiting planetary companion. In a complementary approach, Dr. Najita and post-doctoral fellow Greg Doppmann have used IR molecular absorption spectroscopy to probe the properties of organic molecules in the disk atmosphere of an edge on disk. In another line of investigation, Greg Doppmann, Josh Eisner and Najita have used high resolution IR spectroscopy to explore the origin of the hot compact excess in MWC 480 detect with interferometry. They find no evidence that the emission is due to hot water emission, in contrast with an earlier study, and explore the alternative explanations.

   Bond and Lauretta are studying how extrasolar planetary host stars are chemically distinct from the general stellar population, displaying significant variations in key planet-building elements such as Fe, C, O, Mg, and Si. These enrichments are rimordial in origin, established in the giant molecular cloud from which these systems formed. As a result, the chemistry of planet-building materials in many of these systems is distinctly different from that in our Solar System. Using combined chemical and dynamical modeling (in collaboration with D. O’Brien of the Planetary Science Institute) of planet formation in known extrasolar planetary systems, they have found that terrestrial planets are ubiquitous. Furthermore, the mass and chemistry of these planets is highly variable. For example, errestrial planets similar to Earth are believed to exist in the majority of extrasolar planetary systems while on the other hand systems that are enriched in C, regardless of the actual C abundance, produce terrestrial planets that are dominated by carbide phases. In the context of planet formation models within realistic circumstellar disks, they plan to investigate (with M. Meyer) how these compositional variations influencw the interior structure and processes, surface compositions and features, atmospheric chemistry, and the possibility of life.

   
   

   Illustrated here in this artist's concept, astronomers may have observed the aftermath of a collision between two protoplanets, one Jupiter-sized and one Neptune-sized, in the system 2M1207. (Credit: David A. Aguilar (Harvard-Smithsonian CfA))

   
   Fig 1. Illustrated here in this artist’s concept, astronomers may have observed the aftermath of a collision between two protoplanets, one Jupiter-sized and one Neptune-sized, in the system 2M1207. (Credit: David A. Aguilar (Harvard-Smithsonian CfA))

   
   

   This artist's concept illustrates the idea that rocky, terrestrial worlds like the inner planets in our solar system may be plentiful, and diverse, in the universe.

   
   Fig 2. This artist’s concept illustrates the idea that rocky, terrestrial worlds like the inner planets in our solar system may be plentiful, and diverse, in the universe.

   
   

   This plot of infrared data shows the signatures of water vapor and simple organic molecules in the disk of gas and dust surrounding a young star.

   
   Fig 3. This plot of infrared data shows the signatures of water vapor and simple organic molecules in the disk of gas and dust surrounding a young star.

   Mission Involvement

   PECO

   Meyer is participating in a funded study to assess the feasibility of this mission concept as a probe class mission to search for exoplanets and debris disks around nearby stars.

   JWST

   Meyer serves on the Science Team for the NIRCam and FGS/TFI instruments for the James Webb Space Telescope. He is responsible for star and planet formation science definition, and participates in refining instrument design to enhance related studies.

   Spitzer/HST

   Several team members are involved in a number of programs utilizing the Spitzer Space Telescope and HST to study the formation and evolution of planetary systems by tracing the gas and dust content of cirucmstellar disks around sun-like stars over time.

   Herschel

   Team member Najita is involved in a successful Herschel Key Program directly related to the goals of this module, using Herschel to observe cool gas around sun-like stars at large circumstellar radii.

   SOFIA

   Results from this program will have direct applicability in designing programs for SOFIA related to observations of circumstellar gas and dust.

   Cross-Team Collaborations

   Identify collaborative research with members of other NAI Teams during this reporting period. Include such details as the specific Teams, individuals involved, and the outcome of the collaborations.
   Our Director’s Discretionary Fund award team includes members of CIW (Alan Boss, Larry Nitler, Fred Ciesla), UCLA (Ed Young, Jim Lyons, Mike Jura), U. Hawaii (Sean Andrews), NASA-Ames (Sanford Davis), GSFC (Mike Mumma, Steve Charnley, Avi Mandell).

   In addition we are collaborating with the Harvard Origins of Life initiative and colleagues at MIT to understand theoretical aspects of the formation of planetary systems as well as to understand the suitability of new ground- and space-based telescopes to test these theories.

Publications

Apai, D.  (2008).  A Survey for Massive Giant Planets in Debris Disks with Evacuated Inner Cavities.  ApJ, V672:1196.

Apai., D.  (2008).  Disks around Brown Dwarfs and Cool Stars.  ASPC, V384:383.

Bond, J. et al.  (2008).  Beyond the Iron Peak: r- and s-Process Elemental Abundances in Stars with Planets.  ApJ, 682:1234-1247.

Bouwaman, J. et al.  (2008).  The Formation and Evolution of Planetary Systems: Grain Growth and Chemical Processing of Dust in T Tauri Systems.  ApJ, V683:479.

Carpenter, J.  ().  Formation and Evolution of Planetary Systems Around Sun-like Stars.  ApJ, Submitted.

Carr, J.S.  (2008).  Organic Molecules and Water in the Planet Formation Region of Young Circumstellar Disks.  Science, 319:1504.

Doppmann,, G.W.  ().  Stellar and Circumstellar Properties of the Pre-Main Sequence Binary GV Tau from Infrared Spectroscopy astro-ph/0805.  ApJ, 2426(In press).

Fontani, F.  (2007).  Comparative study of complex N- and O-bearing molecules in hot molecular cores.  A & A, V470.

Greaves, J.  ().  Sub-millimeter Survey for Cold Dust Around 100 Myr Old sun-like Stars in the Pleiades.  MNRAS, Submitted.

Herczeg, G.j.  (2007).  High-Resolution Spectroscopy of [Ne II] Emission of TW Hydrae.  ApJ, V670:509.

Hillenbrand, L.  (2008).  The Complete Census of 70 mm-bright Debris Disks within "the Formation and Evolution of Planetary Systems" Spitzer Legacy Survey of Sun-like Stars.  ApJ, V677:630.

Hines, D.C.  (2007).  The Moth: An Unusual Circumstellar Structure Associated with HD 61005.  ApJ, V671:L165.

Kasper, M.  (2007).  A novel L-band imaging search for giant planets in the Tucana and b Pictoris moving groups.  A & A, V472:321.

Kóspál Á., e.a.  (2008).  High-resolution polarimetry of Parsamina21: revealing the structure of an edge-on FUOri disc.  MNRAS, V383:1015.

Malhotra, R.  (2008).  Prospects for the habitability of OGLE-2006-BLG-109L.  ApJ-Letters, 683:L67-L70.

Mamajek, E.E.  (2007).  An Improbable Solution to the Underluminosity of 2M1207B: A Hot Protoplanet Collision Afterglow.  ApJ(V668):L175.

Meyer, M.R.  (2008).  Evolution of Mid-Infrared Excess around Sun-like Stars: Constraints on Models of Terrestrial Planet Formation.  ApJ, V673:L181.

Moro- Martin, A.  (2008).  Extrasolar Kuiper belt Dust Disks.  In: M.A. Barucci (Ed.).  The Solar System Beyond Neptune (pp. p. 465-480).  Tucson: University of Arizona Press.

Moro-Martin, A.  (2007).  The Dust, Planetesimals and Planets of HD 38529.  ApJ, V668:1165.

Najita, J.R.  ().  CO Fundamental Spectroscopy of V836Tau.  ApJ, In press.

Najita, J.R.  ().  High Resolution K-band Spectroscopy of MWC480 and V1331 Cyg.  ApJ, submitted.

Pascucci, I.  (2007).  Detection of [Ne II] Emission from Young Circumstellar Disks.  ApJ, V663:383.

Pascucci, I.  (2008).  Medium-Separation Binaries Do Not Affect tje First Steps of Planet Formation.  ApJ, V673:477.