Spitzer spectral observations of the deep impact ejecta

Area of Science:

• Cosmic Dust and Planetary Science
• Cometary Science
• Astrochemistry

Background:

• Comets provide insights into the early solar nebula.
• The Deep Impact mission offered a unique opportunity to study cometary ejecta.
• Spectroscopic analysis reveals the composition of cometary materials.

Purpose of the Study:

• To analyze the composition of ejecta from comet 9P/Tempel 1 using Spitzer Space Telescope data.
• To compare the ejecta composition with other cometary and circumstellar materials.
• To infer processes occurring in the early solar nebula based on observed materials.

Main Methods:

• Utilized Spitzer Space Telescope's imaging spectrometer to obtain infrared spectra (5-35 micrometers) of comet 9P/Tempel 1 ejecta.
• Analyzed emission signatures to identify various compounds including silicates, carbon, carbonates, phyllosilicates, polycyclic aromatic hydrocarbons, water, and sulfides.
• Compared the observed spectra with data from comet C/1995 O1 (Hale-Bopp) and the young stellar object HD100546.

Main Results:

• Detected a rich array of materials in the ejecta, including amorphous and crystalline silicates, amorphous carbon, carbonates, phyllosilicates, polycyclic aromatic hydrocarbons, water (gas and ice), and sulfides.
• Found good agreement between the ejecta spectra and materials from comet Hale-Bopp and the circumstellar environment of HD100546.
• Determined atomic abundances consistent with solar and C1 chondritic values, with a dust-to-gas ratio >= 1.3.

Conclusions:

• The observed mixture of materials in comet 9P/Tempel 1 ejecta indicates the presence of both high- and low-temperature phases.
• Efficient annealing of amorphous silicates and large-scale mixing of materials occurred in the early protosolar nebula.
• Cometary composition serves as a valuable archive of conditions and processes in the nascent solar system.