2015 Annual Science Report

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

Exploring the Evolution of the Water and Organic Reservoirs in the Solar System

Project Summary

This project investigates the evolution and stability of water and organic reservoirs in our Solar System, with particular emphasis on the characterization of the current and ancient habitability of planet Mars. We employ extremely powerful observatories (e.g., ALMA, Keck, VLT, future JWST) to acquire high spatial and spectral resolution maps of the isotopic and organic signatures on several bodies in the Solar System. These maps allow us to investigate the stability and evolution of their atmospheres, while localized plumes can be used to identify regions of active release. In this reporting period, we emphasized three areas:

1. We advanced our pioneering work on characterizing the evolution of water on Mars, by developing a new observational plan that combines the power of ALMA, of Keck and of MAVEN to obtain maps of the water D/H signatures on Mars.

2. We identified previously unknown chemical processes affecting singlet-O2 and odd-oxygen on Mars, which may be indicative of a much more active photochemical cycle (with the possible intervention of heterogeneous processes).

3. We provided science leadership in the investigation of Mars with the James Webb Space Telescope (JWST), and established a variety of observing modes and scientific opportunities.

4 Institutions
3 Teams
8 Publications
2 Field Sites
Field Sites

Project Progress

The most comprehensive study of isotopic water in the atmosphere of Mars

During this reporting period, we published the first global maps of HDO and H2O ever achieved for Mars (Villanueva et al., Science 2015). Our infrared measurements of atmospheric D/H on Mars reveal strong geographical variability and a D/H ratio in water much higher (7 VSMOW) than that in Earth’s ocean water, indicative of a significant loss of water from Mars (see Figure 1). The strong geographic and seasonal changes of D/H on Mars may point to the presence of multiple water reservoirs of varying sizes, which lose water to and (may) gain from the atmosphere over time.

Figure 1: Maps of deuterated water (HDO) and water (H2O) and their ratio on Mars (w.r.t. Earth’s ocean water - VSMOW), obtained at four different seasons (from late northern winter to late northern spring). The isotopologue disk maps (HDO, H2O) also reveal strong enhancements and variability but with significant differences among them, associated with global and local climatology. Are these anisotropies related to water release from unrecognized water reservoirs, or due to cloud formation or to an efficient fractionation process? (After Villanueva et al. 2015).

We then advanced our investigation of D/H on Mars, by developing a new observational plan that combines the power of ALMA, Keck and MAVEN to obtain 3D maps of the water D/H signatures on Mars. We were awarded substantial time at these observatories, with the first ever ALMA science observations of Mars to be carried out in March/2016. Vertical profiles of the HDO/H2O abundance to be acquired with ALMA, in concert with escape rates of D and H measured by MAVEN, will provide an unprecedented view of the water cycle on Mars and the significance of atmospheric transport, and will test the presence of additional water reservoirs on the planet.

Taken in context, our work on Mars water informs us of conditions affecting the origin and persistence of life on a second terrestrial planet, including establishing the initial inventory of water and its subsequent losses.

Unidentified chemistry on Mars? Strong tests of current photochemical models via global mapping of water, ozone, and sulfuretted species

For this investigation, we used maps of ozone (probed via O2[a1Δg] dayglow) and water across the Martian globe that we obtained in 2014. Ozone and water are powerful tracers of photochemical processes on Mars. Considering that water is a condensable with a multifaceted hydrological cycle and ozone is continuously being produced / destroyed on short-time scales, their maps can test the validity of current 3D photochemical and dynamical models. Ozone and water are closely linked through photochemistry and they are anticorrelated with each other, because atomic hydrogen (a photolysis product of water vapor) is a powerful catalyst for destroying ozone. Comparisons of maps derived from modern GCM models with our new measurement-based maps point to significant disagreement, which in some cases have been related to heterogeneous (gas-dust) chemistry beyond the classical gas-gas homogeneous reactions.

We also obtained the most sensitive search (ever) for sulphuretted species on Mars by employing radio observatories. This work led to improved limits on active volcanism on Mars (Khayat et al. 2015). It received important media coverage, with several articles reported in international and local newspapers.

Unique Spectroscopy and Imaging of Mars with Space Assets

We led a community-wide white paper on the scientific use of JWST for Mars (Villanueva et al., PASP 2015). The distinctive vantage point of JWST at the Sun-Earth Lagrange point (L2) will allow sampling the full observable disk of Mars, uniquely permitting the study of short-term phenomena, diurnal processes (across the East-West axis) and latitudinal processes between the hemispheres (including seasonal effects) with excellent spatial resolutions (~0.07 arcsec). Spectroscopic observations will be achievable with NIRSpec at a maximum resolving power of 2700 in the 0.7-5 µm spectral region (8000 in the 1-1.25 μm range). Imaging will be attainable with NIRCam at 4.3 μm and with two narrow filters near 2 μm, while the nightside will be accessible with several filters in the 0.5 to 2 μm wavelength range. This powerful suite of instruments will be a major asset for the exploration and characterization of Mars. Science cases include the mapping of the water D/H ratio, investigations of the Martian mesosphere by characterizing the non-LTE CO2 emission at 4.3 μm, studies of chemical transport via observations of the O2 nightglow at 1.27 um, high cadence mapping of the variable dust and water ice clouds, and sensitive searches for trace species and hydrated features on the Martian surface.

We co-authored the first paper describing an infrared spectrometer (NOMAD) on the ExoMars/Trace Gas Orbiter spacecraft (Vandaele et al. 2015). NOMAD will provide unprecedented sensitivity for trace gases (e.g., 25 pptv for methane, in solar occultation) and promises to revolutionize our knowledge of biomarker gases on our sister planet (N2O, CH4, etc.). We continued our participation in the mission preparations, with a more accelerated schedule in the last months of this reporting period, considering the imminent launch on 14 March 2016.

Detailed studies of comets using ground-based observatories:

We also published four papers on cometary science based on data acquired at infrared and millimeter wavelengths, emphasizing their composition based on primary volatiles: H2O, CH3OH, C2H6, NH3, HCN, HC3N, CO, etc. See the GCA project reports by Charnley et al., and DiSanti et al. for this reporting period.

    Geronimo Villanueva Geronimo Villanueva
    Project Investigator
    Michael Mumma

    John Clarke

    Robert Novak

    Alan Tokunaga

    Alain Khayat
    Graduate Student

    Objective 1.1
    Formation and evolution of habitable planets.

    Objective 2.1
    Mars exploration.

    Objective 3.1
    Sources of prebiotic materials and catalysts

    Objective 3.2
    Origins and evolution of functional biomolecules

    Objective 4.1
    Earth's early biosphere.

    Objective 7.1
    Biosignatures to be sought in Solar System materials