2013 Annual Science Report

NASA Jet Propulsion Laboratory - Icy Worlds Reporting  |  SEP 2012 – AUG 2013

Executive Summary

Our goal in the Astrobiology of the Icy Worlds Investigation is to advance our understanding of the role of ice in the broad context of astrobiology through a combined laboratory, numerical, analytical, and field investigations. Icy Worlds team will pursue this goal through four major investigations namely, the habitability, survivability, and detectability of life of icy worlds coupled with “*Path to Flight*” Technology demonstrations.

A search for life linked to the search for water should naturally “follow the ice”. Can life emerge and thrive in a cold, lightless world beneath hundreds of kilometers of ice? And if so, do the icy shells hold clues to life in the subsurface? These questions are the primary motivation of our science investigations which are as follows:

* Habitability of Icy Worlds investigates the habitability of liquid water environments in icy worlds, with a focus on what processes may give rise to life, what processes may sustain life, and what processes may deliver that life to the surface.

* Survivability of Icy Worlds investigates the survivability of biological compounds under simulated icy world surface conditions, and compare the degradation products to abiotically synthesized compounds resulting from the radiation chemistry on icy worlds.

* Detectability of Icy Worlds investigates the detectability of life and biological materials on the surface of icy worlds, with a focus on spectroscopic techniques, and on spectral bands that are not in some way connected to photosynthesis.

* Our technology investigation, a Path to Flight for astrobiology, utilizes instrumentation built with non-NAI funding to carry out the science investigations discussed above. The search for life requires instruments and techniques that can detect biosignatures from orbit and in-situ under harsh conditions. Advancing this capacity is the focus of our Technology Investigation.

The following sections highlight some of our accomplishments for the above investigations.

As far as the Habitability of Icy Worlds investigation is concerned, the following summarizes our progress: Although we had previously produced methane in our serpentinizing experiments involving komatiite and pyrrhotite/pentlandite (reactor), its source, whether scrubbed from source rock or reduced from the CO2 feed, was unclear. In experiments conducted with 99.99% enriched 13CO2, measured 13C-enriched methane present was below the detection limit of the instrument (LOD = 1.8 ppb). However, formate (HCOO-) was generated through the partial reduction of CO2 while at the same time Mg was dissolved from synthetic komatiite. Again we failed to produce the thermodynamically challenging formaldehyde (HCHO).
Membrane experiments continued. The partial transformation of mackinawite to greigite (Fe3S4) reached a maximum of 8% of the sulfide at 70°C to 75°C at which temperature lepidocrocite (ɣ-FeOOH) was also produced. Pyrophosphate was also produced these inorganic membranes as analyzed by nuclear magnetic resonance (NMR).

As part of our Survivability of icy Worlds investigation, The following Co-Is and Collaborators have been conducting research as summarized below. Johnson, Hodyss and Ponce (JPL), carried out spectroscopy and viability of spores in ice; Strazzulla (INAF, Italy), investigated sulfur containing ices under the influence of ion induced radiation processing.

Members of the Investigation 2 team, Paul Johnson, Robert Hodyss, Aaron Noell and Adrian Ponce, along with JPL summer intern Halley Darrach continued an investigation into the spectral properties of bacterial spores in cryogenic ices as well as their viability under solar radiation to find out the answers whether bacterial spores embedded in near surface Europan ice could survive the Jovian radiation environment. If so, Can either the spores or their organic radiolysis products be detected spectroscopically through remote sensing?

Bacillus subtillus was chosen for not only its ability to readily generate spores, but its well-established use as a model species. Briefly, they found that B. subtilis spores generate low molecular weight photoproducts when irradiated with UV at low temperature and pressures (100K and 10-9 Torr).

Collaborator G. Strazzulla of the INAF-Catania Astrophysical Observatory group in collaboration with the group at CIMAP-GANIL in Caen (France) performed experiments on effects induced by fast ions colliding with solids of astrophysical interest. The project is aimed at measuring of formation yields of specific molecules after implantation of reactive (H, C, N, O, S etc), multiply charged ions at different energies in water ice with relevant application to the chemistry of the icy moons in the outer solar system. Based on the experimental results they conclude that sulfur ion implantation is the dominant formation mechanism of hydrated sulfuric acid at Europa.

First in-situ insight into radiation-induced chemical modification of PAHs in astrophysical ice analogs beyond ionization process utilizing a novel 2C-MALDI-TOFMS in combination of UV-radiation-processed PAHs in ice which were desorbed by an IR laser and ionized by a UV laser was reported by Co-I Gudipati. These studies show that even at DMC temperatures of ∼10 K, local UV photons can induce hydrogenation and oxygenation reactions in the ice grains. It is proposed that failure to detect PAHs in high-UV flux regions such as the outer regions of cold, dense clouds or the upper molecular layers of PPDs could be due to rapid radiation processing of these molecules into non-aromatic hydroxylated and hydrogenated hydrocarbons in ices. The studies presented here also show that interstellar ice grains at low-temperatures are nuclei of chemical transformation of organic molecules even at very low temperatures. At higher temperatures corresponding to KBOs and Jupiter family comets, PAHs would be oxidized and hydrogenated much more rapidly, leaving little chance to detect them on icy surfaces.

Co-I C. Sotin and a team of investigators analyzed a sequence of high spatial resolution near-infrared spectra acquired with VIMS at 0.025 s intervals during a 74 km altitude flyover of the South Pole of Enceladus by the Cassini spacecraft on 14 April 2012 UTC. The spectrum was interpreted as thermal emission from a linear fissure and is dominated by the warmest temperature component.

As far as the Detectability of Icy Worlds investigation is concerned, Co-I Hand published two important papers about the surface chemistry of Europa, both partially supported by NAI. Using the Keck II telescope Hand and colleague Mike Brown of Caltech mapped the surface of Europa in the infrared. In the first paper (Brown & Hand, 2013) they described observations of a new spectroscopic feature at 2.07 µm on the trailing hemisphere, which suggests that the trailing hemisphere of Europa may have magnesium sulfate salts produced from the irradiation of endogenous chlorine salts from the subsurface ocean. The results of this paper lead to a two-page highlight in the April 1, 2013 issue of the Time magazine.

In the second paper (Hand & Brown, 2013), they presented the first global map and quantification of the hydrogen peroxide on the surface of Europa.

Part of Investigation 3 involves identification, characterization, and quantification of methane seeping lakes from the permafrost lakes of the Alaskan North Slope. Over the past year our team (Co-I’s Hand, Murray, and Priscu) have collected and analyzed both the methane concentration and isotopic signatures of 8 lakes during Fall and Spring field campaigns (partially funded by NAI, ASTEP, and JPL internal funds).

Co-I Alison Murray and her team discovered bacteria which live under very high levels of reduced metals, ammonia, molecular hydrogen, and dissolved organic carbon, as well as high concentrations of oxidized species of nitrogen (i.e., supersaturated nitrous oxide) and sulfur (as sulfate). The existence of this system, with active biota, and a suite of reduced as well as oxidized compounds, is highly unusual given the millennial scale of its isolation from external sources of energy. The discovery of this ecosystem and the in situ biotic and abiotic processes occurring at low temperature provides a tractable system to study habitability of isolated terrestrial cryoenvironments and is a potential analog for habitats on other icy worlds where water-rock reactions may co-occur with saline deposits and subsurface oceans.