Origins of Life & Habitability

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See CHONDRO I Launch (Failure) video on Youtube.

Also check out our two recent papers on TRAPPIST-1:
- De Wit et al. (2018)
- Bourrier et al. (2017)

NEW: Oxygen and the Potential for Aerobic Life on Mars
Due to the scarcity of O2 in the modern Martian atmosphere, Mars has been assumed to be incapable of producing environments with sufficiently large concentrations of O2 to support aerobic respiration. Here, we present a thermodynamic framework for the solubility of O2 in brines under Martian near-surface conditions. We find that modern Mars can support liquid environments with dissolved O2 values ranging from ~2.5×10−6 mol m−3 to 2 mol m−3 across the planet, with particularly high concentrations in polar regions because of lower temperatures at higher latitudes promoting O2 entry into brines. General circulation model simulations show that Oconcentrations in near-surface environments vary both spatially and with time—the latter associated with secular changes in obliquity, or axial tilt. Even at the limits of the uncertainties, our findings suggest that there can be near-surface environments on Mars with sufficient O2 available for aerobic microbes to breathe. Our findings may help to explain the formation of highly oxidized phases in Martian rocks observed with Mars rovers, and imply that opportunities for aerobic life may exist on modern Mars and on other planetary bodies with sources of O2 independent of photosynthesis.

Get newest Nature Geo paper here: https://rdcu.be/9PhL

Origins & Evolution of Life & Habitability
The evolution of the Earth’s interior below our feet and the tectonic mode strongly impact the redox gradients and the composition of the atmosphere and the crust. The evolution of planet interiors and tectonics, therefore, impact the evolution of life and climate. On the other hand, life and climate impact mantle convection and plate tectonics through the water cycle and rheological modifications of the crust. My major goal is to unite geodynamics with biogeochemistry on land and in oceans in order to fully understand life and climate as a planetary global geophysical phenomenon. A beautiful part of this research is the close link between global and local geophysical modeling and Deep time observations on Earth – of geologic, paleontological, geochemical, and also phylogenetic nature – as well as the connection to planet habitability across the solar system and on exoplanets.


Highlights

  • Observations of the innermost TRAPPIST-1 planets rule out atmospheres largely dominated by cloud-free hydrogen, further supporting the terrestrial and potentially habitable nature of the TRAPPIST-1 planets (De Wit et al., 2018)
  • Combined UV observations, as well as geophysical and atmospheric modeling of outgassing and atmospheric erosion for the TRAPPIST-1 planets suggest that the outer and more massive planets are most likely to still contain greater amounts of liquid water today (Bourrier et al., 2017).
  • Earth with much less water and desert or Dune worlds could be much more common and habitable than previously thought: We explore the minimum distance from a host star where an exoplanet could potentially be habitable in order not to discard close-in rocky exoplanets for follow-up observations. We find that the inner edge of the Habitable Zone for hot desert worlds can be as close as 0.38 AU around a solar-like star, if the greenhouse effect is reduced (∼ 1% relative humidity) and the surface albedo is increased. We consider a wide range of atmospheric and planetary parameters such as the mixing ratios of greenhouse gases (water vapor and CO2), surface albedo, pressure, and gravity. Intermediate surface pressure (∼1–10 bars) is necessary to limit water loss and to simultaneously sustain an active water cycle. We additionally find that the water loss timescale is influenced by the atmospheric CO2 level, because it indirectly influences the stratospheric water mixing ratio. If the CO2 mixing ratio of dry planets at the inner edge is smaller than 10−4, the water loss timescale is ∼ 1 billion years, which is considered here too short for life to evolve. We also show that the expected transmission spectra of hot desert worlds are similar to an Earth-like planet. Therefore, an instrument designed to identify biosignature gases in an Earth-like atmosphere can also identify similarly abundant gases in the atmospheres of dry planets. Our inner edge limit is closer to the host star than previous estimates. As a consequence, the occurrence rate of potentially habitable planets is larger than previously thought.
  • Serpentinization and Fischer-Tropsch type reactions are much more uncertain than what we assumed so far: Serpentinization and Fischer-Tropsch type (FTT) reactions (abbreviated to SFTT reactions) are crucial processes for understanding the origins of life, the limits of conditions for life, and the interactive dynamics of living and non-living systems, as they can provide hydrogen, methane, and other hydrocarbons to fuel life’s origin and its maintenance. However, there is a great lack of agreement on how the kinetics of SFTT reactions change with temperature and pressure, and hence how SFTT reactions vary with depth through a planet’s interior. Suggestions that early life that arose might have survived challenges such as the Late Heavy Bombardment by sustaining itself in the subsurface, make the exploration of the depth-dependent geophysical drivers for the emergence and maintenance of subsurface life through reduced gas production from water-rock reactions an important, but under-investigated aspect of life’s origins and planetary habitability. I aim to assess the depth-dependent kinetics of SFTT reactions along the geotherm by uniting local and global geophysical time-dependent 3D planet interior models with field work in both low-temperature and high-temperature SFTT regions with collaborators across the globe. This approach is novel in its interdisciplinarity and in its goal to not only model local processes but to embed them in a global 3D context of SFTT reactions – giving insight on whether the origin of life was fueled by low-temperature processes within or by high-temperature reactions deep below the “habitable zone”.
  • LIDIA: I developed and performed fluid dynamic experiments in microgravity, on board of ESA’s zero-g parabolic flight air craft, in relation to fluid dynamics and the mitogenic activation of lymphocytes.
  • THE CHONDRO I and II EXPERIMENTS : I created the space experiment Chondro with Georg KellerESA, the ETH Space Biology Institute, and the ETH High Energy Laboratory to study the growth of cartilage in microgravity for tissue engineering. We integrated the first Chondro experiment into Foton M1, a Russian science satellite, and launched it from the Russian cosmodrome Plesetsk in 2002. The final stage of the propulsion system failed and both rocket and experiment fell back and exploded above us. After a complete re-design of the Chondro system – adjusted to manned spaceflight – we were launched it in 2003 with the Cervantes mission from Baikonur to the International Space Station ISS with support from ESA. Analysis of the samples took many years and showed fascinating behavior of cartilage tissue in microgravity.


Further Reading

  • Stamenković, V., Ward, L. M., Mischna, M., Fischer, W. W., 2018. O2 solubility in martian near-surface environments and implications for aerobic life, Nature Geoscience, published online Oct 22 2018.
  • Stamenković, V., 2011, 2015. Serpentinization. In: Gargaud, M., et al., (Eds.), Encyclopedia of Astrobiology, Part 19. Springer, 1505-1506.
  • Zsom, A., Seager, S., De Wit, J., Stamenković, V., 2013. Towards the minimum inner edge distance of the habitable zone. The Astrophysical Journal, 778, 109-126.
  • De Wit, J., et al. (incl. Stamenković, V.), 2018. Atmospheric reconnaissance of TRAPPIST-1’s Habitable Zone Exoplanets. Nature Astronomy, doi:10.1038/s41550-017-0374-z.
  • Bourrier, V., de Wit, J., Bolmont, E., Stamenković, V., + 12 co-authors, 2017. Temporal Evolution of the High-energy Irradiation and Water Content of TRAPPIST-1 Exoplanets. The Astronomical Journal, 154, 121-137.
  • Stamenković, V., Keller, G., Nesic, D., Cogoli, A., Grogan, S.P., 2010. Neocartilage formation in 1 g, simulated, and microgravity environments: implications for tissue engineering. Tissue Engineering: Part A, 16 (5), 1729-1736.
  • Stamenković, V., Keller, G., Walser, S., Fuchsberger, G., 2001. LYMPHOSIG – LIDIA3 Hardware test and behavior of two fluids mixing for T-Lymphocyte investigation on MASER, ESA Erasmus Experiment Archive.
  • Stamenković, V., & Keller, G., 2003. CHONDRO, ESA Erasmus Experiment Archive.
  • Keller, G., & Stamenković, V., 2002. Study of the process of cartilage structure formation in microgravity, ESA Erasmus Experiment Archive.