Abundant molecular oxygen in the coma of comet 67P/Churyumov-Gerasimenko

Dynamic molecular oxygen production in cometary comae

Abundant molecular oxygen was discovered in the coma of comet 67P/Churyumov-Gerasimenko. Its origin was ascribed to primordial gaseous O₂ incorporated into the nucleus during the comet's formation. This thesis was put forward after discounting several O₂ production mechanisms in comets, including photolysis and radiolysis of water, solar wind-surface interactions and gas-phase collisions. Here we report an original Eley-Rideal reaction mechanism, which permits direct O₂ formation in single collisions of energetic water ions with oxidized cometary surface analogues. The reaction proceeds by H₂O⁺ abstracting a surface O-atom, then forming an excited precursor state, which dissociates to produce O₂^-. Subsequent photo-detachment leads to molecular O₂, whose presence in the coma may thus be linked directly to water molecules and their interaction with the solar wind. This abiotic O₂ production mechanism is consistent with reported trends in the 67P coma and raises awareness of the role of energetic negative ions in comets.

Toward biotechnology in space: High-throughput instruments for in situ biological research beyond Earth

Space biotechnology is a nascent field aimed at applying tools of modern biology to advance our goals in space exploration. These advances rely on our ability to exploit in situ high throughput techniques for amplification and sequencing DNA, and measuring levels of RNA transcripts, proteins and metabolites in a cell. These techniques, collectively known as "omics" techniques have already revolutionized terrestrial biology. A number of on-going efforts are aimed at developing instruments to carry out "omics" research in space, in particular on board the International Space Station and small satellites. For space applications these instruments require substantial and creative reengineering that includes automation, miniaturization and ensuring that the device is resistant to conditions in space and works independently of the direction of the gravity vector. Different paths taken to meet these requirements for different "omics" instruments are the subjects of this review. The advantages and disadvantages of these instruments and technological solutions and their level of readiness for deployment in space are discussed. Considering that effects of space environments on terrestrial organisms appear to be global, it is argued that high throughput instruments are essential to advance (1) biomedical and physiological studies to control and reduce space-related stressors on living systems, (2) application of biology to life support and in situ resource utilization, (3) planetary protection, and (4) basic research about the limits on life in space. It is also argued that carrying out measurements in situ provides considerable advantages over the traditional space biology paradigm that relies on post-flight data analysis.

A new model of the chemistry of ionizing radiation in solids: CIRIS

We simulate irradiated O₂ ice, both reproducing measured ozone abundances and predicting the ice thickness of a previous experiment.

PLANET TOPERS: Planets, Tracing the Transfer, Origin, Preservation, and Evolution of their ReservoirS

The Interuniversity Attraction Pole (IAP) 'PLANET TOPERS' (Planets: Tracing the Transfer, Origin, Preservation, and Evolution of their Reservoirs) addresses the fundamental understanding of the thermal and compositional evolution of the different reservoirs of planetary bodies (core, mantle, crust, atmosphere, hydrosphere, cryosphere, and space) considering interactions and feedback mechanisms. Here we present the first results after 2 years of project work.

Observation of stable HO4(+) and DO4(+) ions from ion-molecule reactions in helium nanodroplets

Ion-molecule reactions between clusters of H2/D2 and O2 in liquid helium nanodroplets were initiated by electron-induced ionization (at 70 eV). Reaction products were detected by mass spectrometry and can be explained by a primary reaction channel involving proton transfer from H3(+) or H3(+)(H2)n clusters and their deuterated equivalents. Very little HO2(+) is seen from the reaction of H3(+) with O2, which is attributed to an efficient secondary reaction between HO2(+) and H2. On the other hand HO4(+) is the most abundant product from the reaction of H3(+) with oxygen dimer, (O2)2. The experimental data suggest that HO4(+) is a particularly stable ion and this is consistent with recent theoretical studies of this ion.

Photochemistry of forbidden oxygen lines in the inner coma of 67P/Churyumov-Gerasimenko

Observations of the green and red-doublet emission lines have previously been realized for several comets. We present here a chemistry-emission coupled model to study the production and loss mechanisms of the O(¹S) and O(¹D) states, which are responsible for the emission lines of interest for comet 67P/Churyumov-Gerasimenko. The recent discovery of O₂ in significant abundance relative to water 3.80 ± 0.85% within the coma of 67P has been taken into consideration for the first time in such models. We evaluate the effect of the presence of O₂ on the green to red-doublet emission intensity ratio, which is traditionally used to assess the CO₂ abundance within cometary atmospheres. Model simulations, solving the continuity equation with transport, show that not taking O₂ into account leads to an underestimation of the CO₂ abundance within 67P, with a relative error of about 25%. This strongly suggests that the green to red-doublet emission intensity ratio alone is not a proper tool for determining the CO₂ abundance, as previously suggested. Indeed, there is no compelling reason why O₂ would not be a common cometary volatile, making revision of earlier assessments regarding the CO₂ abundance in cometary atmospheres necessary. The large uncertainties of the CO₂ photodissociation cross section imply that more studies are required in order to better constrain the O(¹S) and O(¹D) production through this mechanism. Space weather phenomena, such as powerful solar flares, could be used as tools for doing so, providing additional information on a good estimation of the O₂ abundance within cometary atmospheres.