2015 Annual Science Report

NASA Goddard Space Flight Center Reporting  |  JAN 2015 – DEC 2015

Interstellar and Nebular Chemistry: Theory and Observations

Project Summary

We continue to undertake theoretical and observational studies pertaining to the origin and evolution of organics in Planetary Systems, including the Solar System. In this performance period, we have focused on studies aimed at understanding the origin and processing of organics in the earliest evolutionary phases of stars like the Sun. These include formation pathways and related isotopic fractionation effects.

We have continued observational programs designed to explore the chemical composition of comets and establishing their potential for delivering prebiotic organic materials and water to the young Earth and other planets. State-of-the-art international facilities are being employed to conduct multi-wavelength simultaneous studies of comets in order to gain more accurate abundances, distributions, temperatures, and other physical parameters of various cometary species. We are also leading an international collaboration to study the organic composition of Titan with the Atacama Large Millimeter Array (ALMA).

4 Institutions
3 Teams
9 Publications
5 Field Sites
Field Sites

Project Progress

We have continued our studies of organic chemistry in the interstellar medium and during the earliest stages of formation of Solar-type stars. These include observational studies of nitrogen fractionation (Wirstrom et al. 2015) and organic molecule production and destruction in the protostellar environment (Taquet et al. 2015). A theoretical study was completed on the formation of complex molecules in the envelopes of protostars undergoing periodic luminosity outbursts, and has been submitted for publication. Our work on the ISM-nebula chemical connection was summarized in a large review paper (Willacy et al. 2015).

A major part of our efforts supported by the NAI are in remote observational programs designed to explore the chemical composition of comets and establishing their potential for delivering pre-biotic organic materials and water to the young Earth and other planets. We have continued a program of interferometric and single-dish mm/sub-mm cometary observations at various observatories in the US and abroad. These include the Atacama Large Millimeter Array (ALMA) in Chile, the Arizona Radio Observatory’s Sub-millimeter Telescope, the JCMT, NRAO GBT 100m and APEX. A study of the volatile production in comet C/2009 P1 (Garradd) was published (Gicquel et al. 2015) and the first detections of ethanol and glycolaldehyde in a comet were reported (Biver et al. 2015). We used ALMA to determine the utility of the methanol molecule for measuring the physical conditions in the coma of comet C/2012 K1 (PanSTARRS) (see Figure 1), and a paper has been accepted for publication.

Figure 1: ALMA flux maps of CH3OH in comet C/2012 K1 (PanSTARRS) observed on 28 & 29 June 2014 at 252 GHz (left) and at 338 GHz (right). White crosses indicate the emission peaks, which are employed as the origin of the coordinate axes. From Cordiner et al. (2015a).

We also contributed to three major reviews concerning cometary composition, isotopic fractionation, and the data required from future laboratory experiments (Cochran et al. 2015; Bockelée-Morvan et al., 2015; Gudipati et al. 2015).

We have continued our successful program of data-mining the ALMA archive, using Titan molecular spectra obtained originally as calibration measurements. During this performance period we published the first spectroscopic detection of ethyl cyanide in Titan’s atmosphere, along with HC3N, CH3CN, and CH3CCH (Cordiner et al. 2015). Surprisingly, ethyl cyanide was enhanced over Titan’s South polar region, while HC3N, CH3CN, and CH3CCH were enhanced over the North (see Figure 2). We also submitted a paper reporting the detection of all C and O isotopologues of CO on Titan.

Figure 2: Integrated emission contour maps for C2H5CN, HC3N, CH3CN and CH3CCH on Titan. The 221-225 GHz continuum is shown in orange. The blue circle rep-resents Titan's surface (dashed white curve is the equator), and the dot-dashed blue line is the polar axis, oriented 2.0 degrees clockwise from vertical. From Cordiner et al. (2015).

    Steven Charnley Steven Charnley
    Project Investigator
    Martin Cordiner

    Stefanie Milam

    Gilless Adande
    Postdoctoral Fellow

    Objective 1.1
    Formation and evolution of habitable planets.

    Objective 1.2
    Indirect and direct astronomical observations of extrasolar habitable planets.

    Objective 2.2
    Outer Solar System exploration

    Objective 3.1
    Sources of prebiotic materials and catalysts

    Objective 3.2
    Origins and evolution of functional biomolecules

    Objective 7.1
    Biosignatures to be sought in Solar System materials

    Objective 7.2
    Biosignatures to be sought in nearby planetary systems