2013 IR&D Annual Report

Capability Development for Modeling Small Icy Bodies in the Solar System,

Principal Investigators
J. Mukherjee
Daniel Boice
W. Huebner
J. Benkhoff (ESA ESTEC)
H. Kawakita (Kyoto Sangyo Univ.)
C. Western (Univ. Bristol)
Chris McKay (NASA Ames)

Inclusive Dates: 07/01/12 – 07/01/13

Background — In 2011, the bright comet Lovejoy made a very close encounter with the Sun, providing a rare opportunity to study the physical properties of sungrazing comets and their coupling to the near-solar environment. Multiple spacecraft observed Lovejoy’s perihelion passage at a variety of wavelengths with spatial resolution. There is much to be learned from this and other sungrazers; however, no comprehensive model exists to aid in the interpretation of these observations. Phosphorus is a key element in all known forms of life, and phosphorus-bearing compounds have been observed in space. It is ubiquitous in meteorites, and it has been detected as part of the dust component in comets, but searches for P-bearing species in the ice phase in comets have been unsuccessful.

Approach — The goal of this project is to adapt SwRI’s general-purpose simulation code of the physical and chemical processes in comets to study the sungrazing comet Lovejoy and the phosphorous chemistry of comets with implications to astrobiology. The innovative model that results will combine SwRI’s codes with two codes supplied by collaborators, extending and enhancing SwRI’s existing capabilities. No computer model currently exists that is capable of addressing the key physical processes and conditions that are thought to be relevant in sungrazing comets in a self-consistent manner as well as likely phosphorous chemistry in comets. Software will be developed that facilitates the comparison of model predictions with ground-based spectral observations needed to reap the full benefits of the model and foster collaborations with observers. The resulting Universal Virtual Spectrometer (UNIVERS) software will be used to address key science issues.


  • Developed a comet model for sungrazing comets by including thermodynamic data for cometary dust that undergo sublimation in the extreme thermal environment experienced by a sungrazer and considered secondary ionization and dissociation processes by energetic photoelectrons.
  • Created the web interface for UNIVERS on a Linux-based server. Sample model output has been used to successfully test the web interface and different aperture sizes have been implemented for development of the instrument modules.
  • Calculated reaction pathways of gas-phase and photolytic chemistry for simple P-bearing molecules likely to be found in comets and important for prebiotic chemistry. The big astronomy news was the surprising discovery of a new sungrazing comet, C/2012 S1 (ISON) that will heighten interest in this work.
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