Kai Finster and Tina Temkiv will give a seminar at the Department of Geoscience on Wednesday next week (20/1).
The overall theme of the seminar will be  “Astrobiology - when Microbiology meets Earth sciences”

This will be a double-impact event where both Tina and Kai will present their work related to exoplanet atmospheres and Martian soil processes with implications for bacterial survival.

The seminar will start at 13.15 in the auditorium at Geoscience and it will be followed by round-table discussions of projects at the interface between astrobiology and Earth sciences.

You are all welcome participate in the seminar and the ensuing discussions (which we expect to start around 14.15).

Abstracts:

Tina Santl Temkiv¹ and Kai Finster^1,2

¹ Stellar Astrophysics Centre, Department of Physics and Astronomy, AU

² Microbiology Section, Department of Bioscience, AU

Part 1:

Atmospheric biosignatures as tools in search for Life on exoplanets.

Šantl-Temkiv T.¹, Ling M.¹, Boesen T.² & Finster K.^1,3

¹Stellar Astrophysics Centre, Department of Physics and Astronomy, Dk, ²Department of Molecular Biology and Genetics, Dk, ³ Department of Bioscience, Dk.

The first exoplanets have been discovered about 20 years ago. Until then, speculations about a second Earth were nothing but science fiction. Thanks to the Kepler mission that has made ground-braking contributions to planetary discovery, we now have a list of almost 2000 confirmed exoplanets. Among the confirmed planets many are found in multiplanetary systems and have earth-like properties in terms of their size, composition, and distance to the central star. The discovery of planetary systems in our galaxy has triggered the need for the development of methods to evaluate whether living organisms are present on exoplanets. Among complementary approaches, the approaches focusing on the study of the atmospheric gas composition have been in the forefront. In particular, the search for gasses that could be produced by organisms, as we know them from Earth, has attracted most attention. The prime candidate is atmospheric oxygen at high concentrations and far from its chemical equilibrium is. We have chosen a different approach that addresses the role of living matter on atmospheric processes such as cloud formation and precipitation. These processes have an impact on the total planetary cloud cover and albedo, which may in future be studied by remote detection techniques. In is seminar I will present our ideas and concepts.

Part 2:

Eroded silicates as sources of hydrogen peroxide, sinks for methane and their implications for bacterial survival.

Bak E.N.¹, Merrison J.P.², Knak Jensen S.³, Nørnberg P. ^1,4 & Finster K.^1,2

¹Department of Bioscience, ²Department of Physics and Astronomy, ³Department of Chemistry, ⁴Department of Geoscience, Aarhus University

The Gas Exchange Experiments (GEx) and the Labeled Release Experiments (LRx) conducted by the Viking Landers demonstrated that the Martian soil releases O₂ upon humidification and contains compounds capable of oxidizing organic matter. This has been attributed to the presence of reactive oxygen species (ROS) in the soil. However, the dominant source of ROS in the Martian soil remains unresolved. Here we show that eroded silicate can oxidize water to the level of hydrogen peroxide (H₂O₂). Taking into consideration the composition of the Martian atmosphere we calculate that reactive wind-eroded silicate on Mars could produce 7 to 31 nmol H₂O₂ per cm³, which would account for the reactivity observed in the LRx and at least partly account for the O₂-release observed in the GEx. Wind erosion thus seems to have a considerable impact on the reactivity of the Martian soil and therefore could affect the durability of organic compounds as well as living organisms on Mars. Furthermore, the reactivity of wind-eroded silicates should thus be considered a potential selective factor during the history of life on Earth and on other silicate planets. Information of the effect of eroded silicates on the survival of different microbial strains is included. In addition, I will present and discuss data that erosion of silicates not only produces reactive oxygen species but that they may also serve as sinks for methane and thereby contribute to the recently reported dynamics of methane in the Martian atmosphere as well as source for methylated chlorites.