Astrobiology, the search for life in the universe, is a multidisciplinary field of research that involves all natural sciences as it connects the origin of life to the evolution of intelligent life forms with the attempt to identify the required environmental settings necessary for life to emerge, maintain and evolve.
Currently prime targets of astrobiological interests are Mars and the ongoing discovery of extra-solar planets, the so-called exoplanets.
Our studies can be summarized by the question: Can erosion of surface silicates produce chemicals that can affect the persistence of organics and of microorganisms in the Martian surface soil?
The essential findings of the three biological experiments on board of the two Viking Mars landers in 1976 indicate the presence of strong oxidants in the Martian topsoil.
It has been proposed proposed that hydrogen peroxide is the most likely candidate. Recently, perchlorate was detected in the Martian surface dust. Perchlorate is a powerful oxidant but despite its high oxidation potential perchlorate is probably not the direct oxidant of organic matter, as it needs higher temperatures than measured on Mars to be activated.
We have addressed the production of reactive mineral phases by erosion processes and could show that eroded silicate can oxidize water to the level of hydrogen peroxide (H2O2) erosion, which could 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. It could also have influence on the composition of the atmosphere. Furthermore, the reactivity of eroded silicates should be considered a potential selective factor during the history of life on Earth and on other siliceous planets and as a mechanism by which hazardous compounds are produced on rocky planets.
We could also demonstrate that eroded silicates react with methane and form covalent Si-C bounds. We propose that this process could be involved in regulating methane dynamics in the Martian atmosphere. Heated in the presence of perchlorate methylated quarts can lead to the formation of methylated chlorides as the “Curiosity“ science team has reported. That means that methylated chlorides- the only type of organics that has been found on Mars yet- are artifacts that could results from the reaction of methylated silicates and perchlorate. Currently we are investigating the effect of eroded silicates on the survival of microorganisms to determine the toxicity of the compounds also for potential Martian biota.
Researchers affiliated with Mars studies:
Svend Knak Jensen Lasse Riis Jensen Silas Bøje Nissen
Here our central research question is: Can (micro)organisms produce biological fingerprints that can be detected and unambiguously identified in the atmosphere of exo-planets which are light years away?
Throughout the past 50 years NASA and ESA have focused on searching for life on Mars and, within the last two decades, on the detection of exo-planets in particular with the implementation of the Kepler space telescope.
The quickly increasing number of discovered and confirmed exo-planets and in particular of Earth-like types indicates that planets are common in the universe and with every new Earth-like planet discovery the possible discovery of Earth-like life becomes more likely. Therefore astrobiologists are working on concepts that would allow distinguishing living- from non-living things either by direct identification or by identifying signatures that can be conclusively affiliated with current or past actions or the presence of living things.
For example, a planets atmosphere with oxygen content of about 20% is a clear sign of a planet in chemical disequilibrium. On Earth the disequilibrium is explained by an imbalance between the amount of oxygen that is released by oxygenic photosynthetic organisms and the removal of oxygen through oxidation reactions of reduced compounds including organic matter due to sedimentation and burial. These types of atmospheric signatures may be looked for when searching for life exo-planets as information on these planets can be transported by light over astronomic distances.
We are approaching the atmosphere as a source on information by elaborating on our work in Aerobiology, which is studying the dispersal of microbes through the atmosphere as well as the microbes’ involvement in cloud and rain formation. We have developed the idea that the contribution of microorganisms to these atmospheric phenomena could be used as a biosignature for life detection on exo-planets.
The idea can be subdivided into the following hypotheses:
1) Microorganisms constitute a significant fraction of aerosols in the atmosphere of a life-bearing planet.
2) A significant fraction of microbes has ice-nucleating (IN) properties and thus enhance cloud and rain formation at higher temperature than in atmospheres that are free of IN bacteria.
3) Next generation telescopes will allow us to study exo-planet atmospheres and thus to look for atmospheric biosignatures.
In order to appreciate the approach one needs to know that pure water starts freezing only at – 38° C. However, we observe that water freezes at much higher temperatures even close to 0° C, which is mainly due to impurities. In Earth atmosphere where the freezing of water is crucial for cloud- and ultimately rain formation, these impurities are provided by aerosols such a mineral dust and sod but also by biological material such as pollen and bacterial cells. In particular bacterial surfaces are of interest as several microbial strains have the capacity to actively produce specialized proteins, the so-called ice-nucleating proteins (INP) that have extremely good ice forming properties and increase the freezing of water far above of what is know from abiological ice-nucleators. These cells may play a significant role in Earth water cycle and it would therefore by extremely interesting to test whether the water cycle would be corrupted in the absence of these cells.
Assuming the possibility of obtaining information on the composition of exo-planet atmospheres, the observation of water clouds in combination with atmospheric temperature profile information on the presences of ice nucleating entities with properties similar to those observed on Earth could be obtained. In combination with other biosignatures such as biogenic gases, the cloud initiating properties of microorganisms could have strong potential as biosignatures.
Through our collaboration with astronomers, atmosphere chemists and molecular biologists at AU and meteorologist at the Danish Meteorological Institute we are working on testing the reliability of that concept and are developing testable hypotheses allowing to critically questioning the idea. Our affiliation with the Stellar Astrophysics basic research center at the Department of Physics and Astronomy provides us with close contact with astronomers that are actively working on identifying exo-planets and on obtaining information on there physical and atmospheric properties. Several of the centre’s fellows are involved in upcoming space missions such as the TESS planet finder mission and the James Web telescope. These involvements provide us with first class opportunities to comparing model results to unprecedented observational data on exo-planets and their atmosphere in the years to come. The timely perspective for the different missions is approximately 10 years, thus leaving sufficient time to develop models and to run experimental validation with laboratory studies. In addition to astronomers we have established collaboration with colleagues at the chemistry department who are specialists in studying the role of aerosols in cloud droplet formation. These colleagues are getting increasingly interested in the role of microorganisms and given the tests beds that they have established there will be excellent facilities at hand to investigate the properties of biological and non biological material and thus to put numbers on their inputs and to investigate the depth whether biological and abiological imprints in the atmosphere can be differentiated by remote sensing with Earth or space based telescopes. The quantitative approach is necessary when it comes to determining the probability of observational data being caused by living or non-living things. The complexity of the problem requests a timely start.
Researchers affiliated with Exo-planet research and Aerobiology:
Kai Finster Morten Dreyer Mads Bendixen
What is going on in the North?
Here our central question is: How does a changing climate affect microbial communities and their activity and vice versa?
Methane is a chemical compound with the formula CH4. It is presented as a colorless and odourless gas with a wide distribution in nature at normal conditions. Methane is the most common organic compound in the atmosphere and one of the major greenhouse gases and its natural and anthropogenic release plays an important role in climate change and global warming. This fact makes methane one of the most studied atmospheric gases so far. Even when the methane concentration in the atmosphere (~1.8 ppm) is much lower than that of carbon dioxide (CO2; ~380 ppm), its impact in the atmosphere is important due to its capacity to absorb infrared radiation (25 times higher than CO2). Microorganisms play an important quantitative role the CH4 cycle. Methanogens are a group of anaerobic Archaea (one of the three domains of living beings), which produces methane that is released to the atmosphere using CO2 and hydrogen or simple organic molecules as sources for methane formation. CH4 is produced by strictly anaerobic methanogens using carbonates (or CO2) as electron acceptors to produce CH4. However, not all the released CH4 reaches the atmosphere because it can be further oxidized to CO2 by the action of methane oxidizing bacteria (methanotrophs). Methanotrophs are a broad group of bacteria that uses CH4 (and derived compounds) as energy and carbon sources and oxidize it partially or totally to CO2 using aerobic respiratory metabolisms. Distinct microbial communities have been found beneath glaciers (subglacial) and within newly exposed glacier forefields (proglacial). When a glacier is receding, it leaves behind a bare area ready to be colonized by invading organisms because these environments often contain considerable amounts of organic carbon sources and bioavailable nutrients. A diverse consortium of bacteria has been found on glacier forefields. The very recently deglaciated zone in front of the glacier is anoxic, due to the removal of dissolved oxygen by microbes beneath the glacier and chemical reactions with reduced compounds and it is frequently inhabited by methanogens, whereas the older deglaciated area is dominated by presence of methanotrophic bacteria and a broader bacterial diversity, due to the adaptation of colonizing microorganisms to the new habitat. Also, the amount and quality of organic carbon source directly affect the abundance and activity of the microbial populations.
There is evidence in deglaciated forelands of methanogenesis processes due to the anoxic conditions and methane release. In addition, methane oxidizing bacteria encounter favorable conditions when the glacier recedes due to an increased access to oxygen although they have so far only been found in old deglaciated sites, probably because of the time-scale adaptation that a new microorganism communities needs to settle down. It has also been suggested that in subglacial sediments, microbial communities are nitrogen limited, reflecting the combined biological activities of organic nitrogen mineralization, nitrification and nitrate reduction. At present, the knowledge on methanogens and methanotrophs in glacial environments is very sporadic and little is known about their specific microbial activities and its long-term role in the global CH4 cycle. Glacier wastage, due to climate warming, may potentially release CH4 from subglacial storage causing a positive feedback on climate warming. To gain a better understanding of these processes it is important to add detailed knowledge about both the structure and the activity of microbial community. Such data will provide valuable information for a better understanding of the consequences of global climate change.
The focus the study is to examine the coupling between glacier retreat and changes in methane fluxes of exposed areas in front of glaciers. This approach will allow to
Researchers affiliated with Arctic Research:
Kai Finster, professor ved Institut for Bioscience, fortæller i radioprogrammet Videnskabens Verden, hvordan han med en model bestående af glasrør, kasser og et hamsterhjul forsørger at fastslå, om der forefindes organisk materiale på Mars.
-Knak Jensen S.J., J. Skibsted, H. J. Jakobsen, I. L. ten Kate, H. P. Gunnlaugsson, J. P. Merrison, K. Finster, E. Bak, J. J. Iversen, J. C. Kondrup and P. Nørnberg. A sink for methane on Mars? The answer is blowing in the wind. Icarus.
- Nørnberg P., E.Bak, K. Finster, H. P. Gunnlaugsson, Knak Jensen S.J and J. P. Merrison. Aeolian comminution experiments revealing surprising sand ball minerals. Aeolian Research
- Hansen A.A., L.L. Jensen, T. Kristoffersen, K. Mikkelsen, J. Merrison, K.W. Finster and B. Aa. Lomstein. (2009). Effects of long-term Martian conditions on a bacterial Permafrost soil community. Astrobiology 9:229-240.
- Jensen L.L, J. Merrison, A. A. Hansen, K. Aa. Mikkelsen, T. Kristoffersen, P. Nørnberg. B. Aa. Lomstein and K. Finster. (2008). Fully automated simulation facility for long-term Mars simulation experiments. Astrobiology 8: 537-548
- Finster K., A. A. Hansen, L.L. Liengaard, K. Mikkelsen, J. Merrison, P. Nørnberg and B. Aa. Lomstein. (2008). The use of complex microbial soil communities in Mars simulation experiments. Int. J. Astrobiol. 7: 169-176.
- Santl Temkiv T., K. Finster and U.G. Bay. Cloud and Atmosphere metagenomics. Encyclopedia of Metagenomics. DOI 10.1007/978-1-4614-6418-1_98-4
-Santl Temkiv, T., K. Finster, B.M. Hansen, L. Pasic and U.G. Karlson. Viable methanotrophic bacteria enriched from air and rain can oxidize methane at cloud-like conditions. Aerobiology published online 23.1.2013: DOI 10.1007/s10453-013-9287-1
- Santl Temkiv, T., K. Finster, T. Dittmar, B.M. Hansen, R. Thyrhaug, N.W. Nielsen, L. Pasic and U.G. Karlson. Hailstones: a window into the microbial and chemical inventory of hailstones. PLOS One published online 23.01.2013: 0.1371/journal.pone.0053550
- Santl Temkiv, T., K. Finster, B. M. Hansen, N. W. Nielsen and U.G. Karlsen. (2012). The microbial diversity of a storm cloud as assessed by hailstones. FEMS Microbiol. Ecol. Online
-Barcena T.G., K.W. Finster and J.C. Yde. (2011) Patterns of development, methane oxidation and methanotrophic diversity in a glacier forefield, southeast Greenland. Arctic, Antarctic and Alpine Research. 43: 178-188.
-Bárcena T.G., J.C. Yde. K.W. Finster. (2010) Methane flux and high-affinity methanotrophic diversity along the chronosequence of a receding glacier in Greenland. Annals og Glaciology, special issue.51:23-31.
-Yde J.C., K.W. Finster, B. Raiswell, J.S. Steffensen, J. Heinemeier, J. Olsen, H.P. Gunnlaugsson, O.B. Nielsen. (2010) Basal ice microbiology at the margin of the Greenland Ice Sheet. Annals of Glaciology, special issue. 51: 71-77.
The Danish National Research Council:
The Danish National Research Foundation:
The Danish Science Foundation: