Titan's Atomic and Molecular Nitrogen Tori

Shematovich et al. (2003) recently showed plasma induced sputtering in Titan's atmosphere is a source of neutral nitrogen in Saturn's magnetosphere comparable to the photo-dissociation source. These sources form a toroidal nitrogen cloud roughly centered at Titan's orbital radius but gravitationally bound to Saturn. Once ionized, these particles contribute to Saturn's plasma. When Titan is inside Saturn's magnetopause, newly formed ions can diffuse inward becoming inner magnetospheric energetic nitrogen where they can sputter and be implanted into icy satellite surfaces. Our 3-D simulation produces the first consistent Titan generated N and N2 neutral clouds; solar UV radiation and magnetospheric plasma subject these particles to dissociation and ionization. The cloud morphologies and associated nitrogen plasma source rates are predicted in anticipation of Cassini data. Since the amount of molecular nitrogen ejected from Titan by photo-dissociation is small, molecular nitrogen ions detection by Cassini will be an indicator of atmospheric sputtering.Comment: Accepted for Publication in Geophysical Research Letter

Science Opportunities offered by Mercury's Ice-Bearing Polar Deposits

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THE JET PROPULSION LABORATORY SUBMILLIMETER, MILLIMETER AND MICROWAVE SPECTRAL LINE CATALOG

Author Institution: Jet Propulsion Laboratory, California Institute of TechnologyThe Jet Propulsion Laboratiory Submillimeter, Millimeter and Microwave Spectral Line Catalog is an on-line computer accessible data base of atmospheric and astrophysical molecules with transitions in the 0 to 10,000 GHz frequencey range. The current fourth edition of the catalog contains 298 species and 1,448,151 lines. The information listed for each spectral line includes the frequency with its estimated error, the intensity, the lower state energy and the quantum number assignment. The catalog has been constructed by using theoretical least squares fits of published spectral lines to accepted molecular models. The resulting predicitions and their error estimates are based on the fitted parameters and their covariances. The catalog is continuously expanded and undated as new data appears. The catalog and the analysis programs used in its generation are available via anonymous ftp at spec.jpl.nasa.gov or on the world wide web at http://spec. jpl.nasa.gov

Investigation of Venus cloud aerosol and gas composition including potential biogenic materials via an aerosol-sampling instrument package

A lightweight, low-power instrument package to measure,&nbsp;in situ,&nbsp;both (1) the local gaseous environment and (2) the composition and microphysical properties of attendant venusian aerosols is presented. This Aerosol-Sampling Instrument Package (ASIP) would be used to explore cloud chemical and possibly biotic processes on future aerial missions such as multiweek balloon missions and on short-duration (&lt;1&thinsp;h) probes on Venus and potentially on other cloudy worlds such as Titan, the Ice Giants, and Saturn. A quadrupole ion-trap mass spectrometer (QITMS; Madzunkov and Nikolić,&nbsp;J Am Soc Mass Spectrom&nbsp;25:1841&ndash;1852, 2014) fed alternately by (1) an aerosol separator that injects only aerosols into a vaporizer and mass spectrometer and (2) the pure aerosol-filtered atmosphere, achieves the compositional measurements. Aerosols vaporized &lt;600&deg;C are measured over atomic mass ranges from 2 to 300 AMU at &lt;0.02 AMU resolution, sufficient to measure trace materials, their isotopic ratios, and potential biogenic materials embedded within H2SO4&nbsp;aerosols, to better than 20% in &lt;300&thinsp;s for H2SO4&nbsp;-relative abundances of 2&thinsp;&times;&thinsp;10&minus;9. An integrated lightweight, compact nephelometer/particle-counter determines the number density and particle sizes of the sampled aerosols.</p

In-Situ Exploration of the Exoplanet Next Door: Revealing the Chemistry, Habitability and Evidence of Biological Processes in the Clouds of Venus

International audienceWith its thick CO2 atmosphere, moonless skies, and proximity to the Sun, Venus is considered to be a close analog to common, presumably lifeless, rocky exoplanets. However, the recent suggestion of PH3 in the clouds of Venus (Greaves et al., 2020) has sparked renewed interest in the prospects for living organisms residing in the skies of Earth's nearest planetary neighbor. As a disequlibrium species, PH3 is readily photolyzed and chemically reacts with H, OH and H2O. In addition, PH3 interacting with the ubiquitous H2SO4 cloud particles readily converts into phosphorous and phosphoric acids (H3PO3 and H3PO4, respectively). Together, these limit the mean lifetime of PH3 molecules in the Venusian clouds to 3 then means that this amount needs to be regenerated approximately every half Earth day. With no known natural photo- or thermo-chemical means to sufficiently generate PH3 from other phosphorus compounds, a working hypothesis is that PH3 is generated by microbial organisms, as occurs on Earth. Irrespective of whether PH3 is eventually confirmed by future observations, in-depth investigation of the present atmosphere of Venus is fundamentally important for understanding mysterious climate history of the planet, as well as the workings of exo-Venuses that are likely going to be the most observable type of exoplanets in the foreseeable future. As proposed by recent mission studies — both a large Flagship class mission (Gilmore et al., 2020) and a more narrowly focused New Frontiers class mission (Baines et al., 2020) — a balloon-based mission to the clouds of Venus would use in-situ measurements to directly investigate the chemistry, dynamics, and potentially biological processes within the cloud environment of our "exoplanet next door". Utilizing the large (~80 m s-1) zonal winds that predominate at o latitude, the aerobot mission concept would circle the planet more than a dozen times over a notional 100-Earth-day science phase as it likely wanders poleward from its deployment near 10o latitude, with an excellent chance of visiting high latitudes >50o. Onboard instrumentation would sample the environment over all times of day including the composition of the air and aerosols, including (1) phosphorous compounds potentially linked to life processes, (2) UV-absorbing materials which possibly are also linked to astrobiology, (3) the reactive sulfur-cycle gases that create the dominant H2SO4 aerosols, and (4) the noble gases, their isotopes and the isotopes of light gases — key to understanding the formation and evolution of the planet and its atmosphere. A digital holographic microscope would image particles in three dimensions at 0.7 micron-scale spatial resolution, searching for cellular morphologies. The balloon mission also directly and continuously measures the pressure/temperature structure, and, supported by balloon-tracking orbiter, winds in all three dimensions. The aerobot, capable of multiple 10-km-altitude traverses centered near 55-km (~0.5 bar, 25C), would enable 3-dimensional maps of these environmental characteristics as well as the dynamically/chemically influenced size distribution of aerosol particles via a nephelometer/particle-counter(Renard et al., 2020) testing, for example, the life cycle hypothesis of Seager et al (2020). These traverses also reveal the vertically-varying characteristics of atmospheric stability, gravity and planetary waves and Hadley cells, important for understanding the mechanisms that power and sustain the planet's strong super-rotation. Such altitude excursions also enable measurements of radiative balance and solar energy deposition via a Net Flux Radiometer (Aslam et al., 2015), another key to understanding super-rotation. References: Aslam, S., et al. (2015) EPSC Abstracts, Vol 10. EPSC2015-388. Baines, K. H. et al. (2020). New-Frontiers Class In-Situ Exploration of Venus: The Venus Climate and Geophysics Mission Concept. White paper submitted to Planetary Science Decadal Survey 2023-2032. Gilmore, M.S., Beauchamp. P. M., Lynch, R., Amato, M. J., et al. (2020). Venus Flagship Mission Decadal Study Final Report. https://www.lpi.usra.edu/vexag/reports/Venus-Flagship-Mission_FINAL.pdf Greaves JS., Richards MS., Bains W. et al. (2020) Phosphine in the cloud decks of Venus. Nature Astronomy doi.org/10.1038/s41550-020-1174-4. Renard, J.-B., Mousis, O., Rannou, P., Levasseur-Regourd, A. C., Berthet, G., Geffrin, J.-M., Hadamcik, E., Verdier, N., Millet, A.-L., and Daugeron, D. (2020) Counting and phase function measurements with the LONSCAPE instrument to determine physical properties of aerosols in ice giant planet atmospheres, Space Science Reviews, 206, 28. Seager S, Petkowski JJ, Gao P, et al. (2020) A proposed life cycle for persistence of the Venusian aerial biosphere. Astrobiology 2021, 21:2. DOI: 10.1089/ast.2020.224