Planetary Astronomy Late-morning Seminar for 2018-04-23

Series: Planetary Astronomy Late-morning Seminar
Date: Monday 23-Apr-2018
Time: 11:15-12:15
Location: ATL 1250
Speaker: Sara Faggi (GSFC)
Title: The Volatile Composition of comets: The newly-discovered C/2017 E4 (Lovejoy) before its dissolution as revealed by iSHELL at NASA/IRTF

Comets are considered the most pristine bodies of the solar system and their investigation through cosmogonic parameters provides important information on native conditions in the solar nebula. Our knowledge about infant stages of our planetary system is still fragmentary and cometary nuclei retain the least processed material from that era. Investigation of comets composition, based on cosmogonic indicators, is essential for testing models of Solar System formation and evolution, for assessing cometary delivery of organic compounds to the early Earth, and for addressing the origin of water on Earth.

In April 2017, we acquired comprehensive high-resolution spectra of newly-discovered comet C/2017 E4 (Lovejoy) as it approached perihelion, and before its disintegration. We detected many cometary emission lines across 4 customized instrument settings (L, L3, Lp1 and M1) in the (1.1 – 5.2) micron range, using iSHELL - the new near-IR high resolution immersion echelle spectrograph on NASA/IRTF (Mauna Kea, Hawaii).

Around 3 microns, in L1, we detected fluorescence emission from HCN, C2H2, water, prompt emission from OH, and many other features. Methane, ethane and methanol were detected both in L3 and Lp1 settings. These species are relevant to astrobiology, owing to questions regarding the origin of pre-biotic organics and water on terrestrial planets. In M1, near 5 micron, we detected multiple ro-vibrational lines of H2O, CO and the (X-X) system of CN; the latter data constitute a complete survey of CN at these wavelengths.

The many water emission lines detected in L1 and M1 provided an opportunity to retrieve independent measures of rotational temperature for ortho- and para-H2O, thereby reducing systematic uncertainty in the derived ortho-para ratio and nuclear spin temperature. Deuterated species were also sought and results will be presented.

The bright Oort cloud comet E4 Lovejoy combined with the new capabilities of iSHELL provided unique results. The individual iSHELL settings cover very wide spectral range with very high accuracy, eliminating many sources of systematic errors when retrieving molecular abundances; future comparisons amongst comets will clarify the nature and meaning of cosmogonic indicators based on composition.

For further information contact PALS coordinator Dr. Matthew Knight at or (301)-405-2629.


Special accommodations for individuals with disabilities can be made by calling (301) 405-3001. It would be appreciated if we are notified at least one week in advance.


Directions and information about parking can be found here.

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