Electron bombardment of Europa

Paranicas, C.; Carlson, R. W.; Johnson, R. E.

doi:10.1029/2000gl012320

Cited by 119 publications

(186 citation statements)

References 18 publications

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“…More than 80% of the irradiation energy is from electrons that range in energy from a few eV to ϳ10 MeV (Cooper et al, 2001;Paranicas, 2001). In addition, protons and heavier ions create cascades of secondary electrons.…”

Section: Europa's Surface Energy Fluxmentioning

confidence: 99%

Energy, Chemical Disequilibrium, and Geological Constraints on Europa

2007

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Europa is a prime target for astrobiology. The presence of a global subsurface liquid water ocean and a composition likely to contain a suite of biogenic elements make it a compelling world in the search for a second origin of life. Critical to these factors, however, may be the availability of energy for biological processes on Europa. We have examined the production and availability of oxidants and carbon-containing reductants on Europa to better understand the habitability of the subsurface ocean. Data from the Galileo Near-Infrared Mapping Spectrometer were used to constrain the surface abundance of CO 2 to 0.036% by number relative to water. Laboratory results indicate that radiolytically processed CO 2 -rich ices yield CO and H 2 CO 3 ; the reductants H 2 CO, CH 3 OH, and CH 4 are at most minor species. We analyzed chemical sources and sinks and concluded that the radiolytically processed surface of Europa could serve to maintain an oxidized ocean even if the surface oxidants (O 2 , H 2 O 2 , CO 2 , SO 2 , and SO 4 2؊ ) are delivered only once every ϳ0.5 Gyr. If delivery periods are comparable to the observed surface age (30-70 Myr), then Europa's ocean could reach O 2 concentrations comparable to those found in terrestrial surface waters, even if ϳ10 9 moles yr ؊1 of hydrothermally delivered reductants consume most of the oxidant flux. Such an ocean would be energetically hospitable for terrestrial marine macrofauna. The availability of reductants could be the limiting factor for biologically useful chemical energy on Europa. Keywords: Europa-Radiolysis-Oxygen-Habitability-Planetary science. Astrobiology 7, 1006-1022. INTRODUCTION WHILE THE MANTRA of "follow the water" has been the call of NASA's search for life beyond Earth, it is really a subset of the mantra "follow the energy." Life as we know it-that is, all life on Earth-requires just two forms of energy: thermal energy for melting water and chemical energy for maintaining and regulating processes considered essential for life. Even organisms that directly absorb light, e.g., for photosynthesis, do so as a means of producing utilizable chemical energy, stored in ATP.The existence of liquid water on any world in our contemporary cold universe (2.725 Ϯ 0.002 K) is the result of energy production (Mather et al., (Haida et al., 1974). Traditional definitions of the habitable zone have, in part, been restricted to liquid water on the surface of Earth-like planets made possible in part by atmospheric and surface heating from the parent star (Kasting et al., 1993). Such definitions of "surface habitability" cannot (nor were they intended to) take into account two energy sources that may be responsible for maintaining the majority of liquid water in our solar system, if not the universe: tidal and radiogenic energy.Within the jovian system, the generation of thermal energy through tidal dissipation and radioactive decay (following initial accretional heating) accounts for what are likely our solar system's three largest oceans. At present, the evid...

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Section: Europa's Surface Energy Fluxmentioning

confidence: 99%

Energy, Chemical Disequilibrium, and Geological Constraints on Europa

2007

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“…For the trailing hemisphere, lower energy 179 electrons have access to a larger range of latitudes, while the electrons with energies 180 just below the resonance energy are confined to a narrow region near the equator. This 181 is the basis for the lens-like electron bombardment pattern, which has been studied 182 extensively for both Europa (Paranicas et al, 2001;Patterson et al, 2012) and Saturn's 183 moons (Paranicas et al, 2012(Paranicas et al, , 2014Schenk et al, 2011). 184…”

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The near-surface electron radiation environment of Saturn's moon Mimas

Nordheim

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Paranicas

et al. 2017

Icarus

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16Saturn's inner mid-size moons are exposed to a number of external weathering 17 processes, including charged particle bombardment and UV photolysis, as well as 18 deposition of E-ring grains and interplanetary dust. While optical remote sensing 19 observations by several instruments onboard the Cassini spacecraft have revealed a 20 number of weathering patterns across the surfaces of these moons, it is not entirely clear 21 which external process is responsible for which observed weathering pattern. Here we 22 focus on Saturn's moon Mimas and model the effect of energetic electron bombardment 23 across its surface. By using a combination of a guiding center, bounce-averaged 24 charged particle tracing approach and a particle physics code, we investigate how the 25 radiation dose due to energetic electrons is deposited with depth at different locations. 26

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“…The similar depth scales for the electron penetration, thermal skin depth, and enhanced UV scattering provides strong support for the hypothesis that high energy electrons are responsible for the increased thermal inertia in the anomalous regions. Similar weathering features due to trapped magnetospheric plasma have also been identified on Europa [Paranicas et al, 2001].…”

Section: Measured Electron Propertiessupporting

confidence: 50%

Radiation Effects on Airless Bodies in Space: Radiolysis, Sputtering, and Sintering in Regoliths

Schaible¹

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Electron bombardment of Europa

Cited by 119 publications

References 18 publications

Energy, Chemical Disequilibrium, and Geological Constraints on Europa

Energy, Chemical Disequilibrium, and Geological Constraints on Europa

The near-surface electron radiation environment of Saturn's moon Mimas

Radiation Effects on Airless Bodies in Space: Radiolysis, Sputtering, and Sintering in Regoliths

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