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Research

Lab Work

Lab Investigation 1: The Habitability of Icy Worlds investigation has three major objectives. Objective 1, Seafloor Processes, explores conditions that might be conducive to originating and supporting life in icy world interiors. Objective 2, Ocean Processes, investigates the formation of prebiotic cell membranes under simulated deep-ocean conditions, and Objective 3, Ice Shell Processes, investigates astrobiological aspects of ice shell evolution.

As part of this investigation 1, Co-I's Drs. Russell and Kanik and team carried out a series of "origin of life" experiments using a hydrothermal vent reactor (Fig 1).

chart
Figure 1.
JPL Icy Worlds team researchers, Russell and Kanik, are experimentally testing the theory that life may have emerged ~4 billion years ago within porous and partly permeable submarine, moderate-temperature (=100°C) alkaline hydrothermal springs on any wet, rocky planet or satellite in our solar system. Simulation experiments at JPL, modeling 4 billion-year-old hydrothermal mound, designed to test this theory, is shown.

The first experiment involved the interaction of carbonic and ammoniacal fluids with ultramafic silicate rock and sulfide such as would be found comprising the crust of our own and other wet (icy) rocky worlds. This experiment produced formate and amino acids, in particular alanine>>glycine>>serine and epsilon amino-n-caproic acid. Peptides and various amines are also recorded. This paper set the scene for further experimentation.

Co-I Dr. Goodman and his students used the supercomputer system at Wheaton College to run three-dimensional plume dynamics models comparing the size, velocity, and temperature of plumes, incorporating equations of state for MgSO4 and water that take into account pressure-dependence of thermal expansion and heat capacity, properties held constant in conventional dynamics models for Earth's oceans. Goodman also developed a single-column convection model, which will allow exploration the overall vertical structure of Europa's ocean on a global scale.

Co-I's Professor Brown and Dr. Vance conducted a focused set of sound velocity measurements in aqueous ammonia (a proxy for Titan's ocean). Comparing new results with previous equations of state for solution density (Croft et al. 1988), they find that these previous results do not produce self-consistent forward-modeling results for sound velocity. Moreover, the new results reveal that sound velocities in aqueous ammonia show less concentration dependence than previously expected. Corresponding specific volumes (densities) are universally lower than previously predicted, strengthening arguments against extrusive ammonia-water cryo-volcanism on Titan.

Co-I Dr. Choukroun continued investigating clathrate formation, stability and dynamics and clathrate's role in ice shell evolution in the astrobiological context. Experimental work examines the creation of clathrate hydrates. Computational modeling of ice shell convection tracks the shuttling of these and other biorelevant materials between oceans and surfaces, and also examines the possibility of "sub-glacial" lakes as briny oases within the ice.

Lab Investigation 2: The Survivability of Icy Worlds investigation examines the survivability of biological compounds under simulated icy world surface conditions, and compares the degradation products to abiotically synthesized compounds resulting from the radiation chemistry on icy worlds.

Co-Investigator Murthy Gudipati and his group focused on the spectroscopy of ices and ices containing PAH impurities under UV and electron irradiation, aiming at understanding the chemistry of icy solar system surfaces such as Europa. In particular they have been successful in commissioning MALDI-TOF-MS experiment to investigate water-ices at any given temperature between 5 and 200 K. To the best of our knowledge, there are only two labs that dedicate to study chemistry in water-ice using MALDI-TOF-MS, one of them situated in France and the other Dr. Gudipati's "ice spectroscopy lab, ISL" at JPL. Our ongoing NAI Icy worlds research has shown that PAHs are ionized with low-energy UV-VIS photons, due to lowering of the ionization energy in ice environment. We extended these studies to a variety of PAHs such as Pyrene, Perylene, Tetracene, and Porphyrin (a model biomolecule). The results are summarized in Figure 2-2.

Diagram
Figure 2-2.
Ionization of PAHs Perylene, Tetracene, and Pyrene imbedded in water-ice as impurities - simulating the cometary, and outer solar system icy surfaces. These molecules are ionized with tunable OPO lasers at wavelengths shown by arrows in the figure. The corresponding ionization energies in ice surrounding are at least 2-3 eV below the ionization energies of these molecules in the gas-phase.

As a part of Lab Investigation 2, Co-Investigators Paul Johnson, Robert Hodyss have continued studying the photolysis of organic molecules in icy matrices relevant to solar system bodies. Their goal is to determine the precise chemical pathways that various molecules evolve in analog solar system ices as a function of temperature and wavelength. This involves photolysis of organics in ice, pure organics, matrix isolated organics, and organics under a layer of peroxide (to provide a source of hydroxyl radicals). Addition baseline spectra are also taken of suspected products to confirm identifications. They are measuring the photolytic lifetimes of hydrocarbons in both water and nitrogen matrices. They are also studying the photolytic chemistry of amino acid (glycine) and lipid (oleic acid and 1-stearoyl-2-linoleoyl-sn-glycero-3-phosphocholine; SLPC) degradation through matrix isolation experiments.

Also as a part of lab Investigation 2, Co-I Dalton has demonstrated that surface deposits on Europa contain both hydrated salts, frozen brines and sulfuric acid (Dalton et al., 2011a). This confirms predictions of Carlson et al., (2005) that a radiolytic sulfur cycle is responsible for creation of sulfuric acid hydrate via chemical processing driven by magnetospheric charged particle bombardment. Dalton has now mapped the sulfuric acid distribution using Galileo Near-Infrared Mapping Spectrometer (NIMS) observations, and compared the sulfuric acid abundances with models of electron and ion energy deposited into the surface (Dalton et al., 2011b).

And finally, as a part of lab Investigation 2, Co-investigator Dr. Cooper and group have been exploring the possibility of oxidant (O2 and H2O2) formation, for the interpretation of both surface and atmospheric composition of icy satellites, due to surface reactions of OH. The group has recently shown that methanol (CH3OH) was produced from the reaction of CH4 and O(1D) which is the dominant reaction channel for methanol formation although this reaction channel is mostly ignored in the literature in favor of the CH3 + OH reaction. They are continuing the matrix isolation work and will be extending to ice work in the near future to assess the relative importance of these channels in methanol formation.

Investigation 3: Detectability of Life investigates the detectability of chemical and biological signatures 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. The Detectability of life investigation has three major objectives: Detection of Life in the Laboratory, Detection of Life in the Field, and Detection of Life from Orbit. As part of the Investigation, Hand and colleagues have identified and map lakes that may be releasing large quantities of methane using data from the Moderate Resolution Imaging Spectroradiometers (MODIS) onboard the Terra and Aqua satellites. These satellites get near daily coverage of the Alaskan North Slope and one of the data products is a snow and ice coverage map for the region. Click here for more information about the detectability investigations in the field and all Field Site Research investigations.