Search

The surface environmental conditions of many of the icy ocean worlds in the Solar System are outside of the thermal stability field of methane ice. However, mechanisms may exist that entrain or trap methane within water ice that arrives at the surface via plume eruptions or resurfacing events. At the surface, the ice grains may experience charged particle irradiation that could lead to the production of new complex hydrocarbons. We investigated the irradiation products of 12CH 4 versus 13CH 4 , the temperature dependence of CH 4 radiation processing and product stability, and the temperature stability of CH 4 when mixed with H 2 O in a cryogenic vacuum environment. Significantly, methane ice experimentally encased in water ice was irradiated at 100 K in an ultra-high vacuum environment and produced similar radiation-formed secondary phases as pure methane ice irradiated at 20 K. The methane radiation products produced outside of the methane ice thermal stability field, while encased in a water ice film, were most notably 13CO 2 and a candidate hydrocarbon feature. Evidence for complex hydrocarbons, such as C 2 H 6 , was observed during warming and sublimation of the sample. • The radiolysis of CH 4 ices at ocean world environmental conditions was investigated. • CH 4 ice inside H 2 O ice irradiated at 100 K created similar secondary phases as CH 4 ice. • The temperature dependence of CH 4 and CH 4 +H 2 O radiation processing was investigated. [ABSTRACT FROM AUTHOR]

Numerous investigations have measured and identified properties of water and exotic ices. These properties are measured at various pressures and temperatures; however, these disparate studies are sometimes difficult to find, confusing, or even contradictory. Here, we amass and present a catalogue of some temperature dependent equations on ice density, latent heat of fusion, constant values for latent heat of sublimation, specific heat capacity at constant pressure, thermal conductivity, and Arrhenius flow law parameters for water ice, carbon dioxide ice, and solid nitrogen. The equations are either directly cited from the sources or are fitted from data in past publications. [ABSTRACT FROM AUTHOR]

The surface of Europa is heavily irradiated by high-energy particles with the energy ranges of 1–100 MeV for primary electrons and ∼10 keV for secondary electrons. These irradiations may cause oxidation of surface materials, such as chlorides and sulfur-bearing species, through reactions with oxidative radicals formed by dissociation of H 2 O ice. Similar irradiation-induced oxidation could have occurred in near-surface ice on Mars. However, most of previous experiments simulated ∼10 keV electron irradiation onto ice materials on Europa and Mars, and few studies have investigated the oxidation of chlorides and sulfur by MeV electron irradiation. Here we performed laboratory experiments on MeV electron irradiation, as well as 10 keV electron and UV irradiations, onto mixtures of H 2 O ice and chlorides, or elemental sulfur, at low temperatures. Our experimental results indicate selective oxidation of sulfur against chlorides, with negligible formation of oxychlorides on irradiation of H 2 O ice and chloride mixtures, regardless of experimental conditions (temperature, electron energy, or presence of oxidants in ice). Sulfate is effectively formed by the electron irradiation. This selective oxidation may be caused by the different stabilities of atoms within irradiated H 2 O ice. If sulfate on Europa's surface is transported into the subsurface ocean, this could provide energy sources for possible chemoautotrophic life in the ocean. On Europa, sulfur would be one of key elements in redox chemistry on the surface and possibly in the subsurface ocean. • Laboratory experiments on irradiation-induced oxidation on planetary surface. • MeV and 10 keV electron irradiation onto mixtures of H 2 O ice and chlorides or sulfur. • Selective oxidation of sulfur against chlorides, with negligible formation of oxychlorides. • Sulfur would be one of key elements in redox chemistry on Europa. [ABSTRACT FROM AUTHOR]