Zentrum für Astronomie und Astrophysik

76 Items

Recent Submissions
The Case (or Not) for Life in the Venusian Clouds

Schulze-Makuch, Dirk (2021-03-20)

The possible detection of the biomarker of phosphine as reported by Greaves et al. in the Venusian atmosphere stirred much excitement in the astrobiology community. While many in the community are adamant that the environmental conditions in the Venusian atmosphere are too extreme for life to exist, others point to the claimed detection of a convincing biomarker, the conjecture that early Venus...

Brightness modulations of our nearest terrestrial planet Venus reveal atmospheric super-rotation rather than surface features

Lee, Yeon Joo ; García Muñoz, Antonio ; Imamura, T. ; Yamada, M. ; Satoh, T. ; Yamazaki, A. ; Watanabe, S. (2020-11-12)

Terrestrial exoplanets orbiting within or near their host stars’ habitable zone are potentially apt for life. It has been proposed that time-series measurements of reflected starlight from such planets will reveal their rotational period, main surface features and some atmospheric information. From imagery obtained with the Akatsuki spacecraft, here we show that Venus’ brightness at 283, 365, a...

Machine Learning Algorithms Applied to Identify Microbial Species by Their Motility

Riekeles, Max ; Schirmack, Janosch ; Schulze-Makuch, Dirk (2021-01-12)

(1) Background: Future missions to potentially habitable places in the Solar System require biochemistry-independent methods for detecting potential alien life forms. The technology was not advanced enough for onboard machine analysis of microscopic observations to be performed in past missions, but recent increases in computational power make the use of automated in-situ analyses feasible. (2)...

Editorial: Presentations at the 4th Workshop of the German Astrobiological Society (DAbG) on Astrobiology, 26–27 September 2019, Vienna, Austria

Milojevic, Tetyana ; De La Torre Noetzel, Rosa ; Strbak, Oliver ; Schulze-Makuch, Dirk (2021-01-18)

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Supporting Information and Data for Machine Learning Algorithms Applied to Identify Microbial Species by their Motility

Riekeles, Max (2020)

Future missions to potentially habitable places in the Solar System require biochemistry-independent methods for detecting potentially alien life forms, for which ‘motility’ is an excellent candidate. Here we present a semi-automated experimental setup, capable of distinguishing the movement of abiotic particles due to Brownian motion from the motility behavior of the bacteria Pseudoalteromonas...

Habitability of terrestrial planets around active M-stars: the effect of stellar radiation and cosmic rays upon climate and photochemistry

Scheucher, Markus (2021)

Planetary habitability depends strongly on the interaction between the planetary atmosphere and the energy from its host star. Due to both the anticipated diversity of exoplanetary atmospheres as well as the large range of stellar classes and activities, modeling possible planetary climate states and atmospheric conditions is a challenging endeavor. A central aim of this work was to extend the ...

The influence of magma ocean crystallization on mantle dynamics

Maurice Olivier, Maxime (2020)

The early stages of terrestrial planets evolution play a crucial role in determining their long-term development. In particular, the differentiation between an iron core and a silicate mantle is likely followed by the crystallization of a primordial magma ocean, controlling the initial conditions for solid-mantle thermal and dynamical evolution. Because it was thought that magma ocean crystalli...

Matrix-propagator approach to compute fluid Love numbers and applicability to extrasolar planets

Padovan, Sebastiano ; Spohn, T. ; Baumeister, Philipp ; Tosi, Nicola ; Breuer, D. ; Csizmadia, Sz. ; Hellard, H. ; Sohl, F. (2018-12-12)

Context. The mass and radius of a planet directly provide its bulk density, which can be interpreted in terms of its overall composition. Any measure of the radial mass distribution provides a first step in constraining the interior structure. The fluid Love number k2 provides such a measure, and estimates of k2 for extrasolar planets are expected to be available in the coming years thanks to i...

Carbon cycling and interior evolution of water-covered plate tectonics and stagnant-lid planets

Höning, Dennis ; Tosi, Nicola ; Spohn, Tilman (2019-07-01)

Aims. The long-term carbon cycle for planets with a surface entirely covered by oceans works differently from that of the present-day Earth because inefficient erosion leads to a strong dependence of the weathering rate on the rate of volcanism. In this paper, we investigate the long-term carbon cycle for these planets throughout their evolution. Methods. We built box models of the long-term c...

Lagrangian statistics for dispersion in magnetohydrodynamic turbulence

Pratt, Jane ; Busse, Angela ; Müller, Wolf-Christian (2020-10-26)

Measurements in the heliosphere and high‐resolution fluid simulations give clear indications for the anisotropy of plasma turbulence in the presence of magnetic fields. How this anisotropy affects transport processes like diffusion and dispersion remains an open question. The first efforts to characterize Lagrangian single‐particle diffusion and two‐particle dispersion in incompressible magneto...

Bayesian modelling of nuclear fusion experiments

Kwak, Sehyun (2020)

Bayesian probability theory as a general framework for scientific modelling and inference is introduced and applied to nuclear fusion experiments in order to provide consistent inference solutions given multiple heterogeneous data sets. Fusion plasmas are complex physical systems, in which charged particles are confined by the electromagnetic force. The physics parameters of the plasmas involve...

Spatial and Temporal Variability of the 365‐nm Albedo of Venus Observed by the Camera on Board Venus Express

Lee, Yeon Joo ; Kopparla, P. ; Peralta, J. ; Schröder, S. E. ; Imamura, T. ; Kouyama, T. ; Watanabe, S. (2020-06-15)

We mapped the distribution of the 365‐nm albedo of the Venus atmosphere over the years 2006–2014, using images acquired by the Venus Monitoring Camera (VMC) on board Venus Express. We selected all images with a global view of Venus to investigate how the albedo depends on longitude. Bertaux et al. (2016, https://doi.org/10.1002/2015JE004958) reported a peak in albedo around 100° longitude and s...

The Astrobiology of Alien Worlds: Known and Unknown Forms of Life

Irwin, Louis N. ; Schulze-Makuch, Dirk (2020-08-20)

Most definitions of life assume that, at a minimum, life is a physical form of matter distinct from its environment at a lower state of entropy than its surroundings, using energy from the environment for internal maintenance and activity, and capable of autonomous reproduction. These assumptions cover all of life as we know it, though more exotic entities can be envisioned, including organic f...

Lagrangian Statistics of Heat Transfer in Homogeneous Turbulence Driven by Boussinesq Convection

Pratt, Jane ; Busse, Angela ; Müller, Wolf-Christian (2020-08-03)

The movement of heat in a convecting system is typically described by the nondimensional Nusselt number, which involves an average over both space and time. In direct numerical simulations of turbulent flows, there is considerable variation in the contributions to the Nusselt number, both because of local spatial variations due to plumes and because of intermittency in time. We develop a statis...

Constraining the interiors of exoplanets with the Love number h2

Hellard, Hugo Gwenolé Samuel (2020)

The fascinating diversity in the properties of extrasolar planets and planetary systems, compared to those of the Solar System, has challenged our understanding of planetary formation and evolution. The interior of a planet holds traces of its history, and is thereby the present witness of the processes involved during its formation and evolution. The Love numbers, introduced by A.E.H. Love in ...

Machine learning approximation of Bayesian inference in nuclear fusion research

Pavone, Andrea (2020)

Machine learning algorithms, especially neural networks, are commonly used to automatically find and encode unknown relationships between sets of related data. They have been applied to problems in different fields, including the interpretation of data in scientific experiments. In this thesis, I consider the case where the relationship between a set of observed data and modeling parameters is...

Physicochemical Salt Solution Parameters Limit the Survival of Planococcus halocryophilus in Martian Cryobrines

Waajen, Annemiek C. ; Heinz, Jacob ; Airo, Alessandro ; Schulze-Makuch, Dirk (2020-07-07)

Microorganisms living in sub-zero environments can benefit from the presence of dissolved salts, as they significantly increase the temperature range of liquid water by lowering the freezing point. However, high concentrations of salts can reduce microbial growth and survival, and can evoke a physiological stress response. It remains poorly understood how the physicochemical parameters of brine...

A New Record for Microbial Perchlorate Tolerance: Fungal Growth in NaClO4 Brines and its Implications for Putative Life on Mars

Heinz, Jacob ; Krahn, Tim ; Schulze-Makuch, Dirk (2020-04-28)

The habitability of Mars is strongly dependent on the availability of liquid water, which is essential for life as we know it. One of the few places where liquid water might be found on Mars is in liquid perchlorate brines that could form via deliquescence. As these concentrated perchlorate salt solutions do not occur on Earth as natural environments, it is necessary to investigate in lab exper...

Numerical modeling of magma ocean solidification and concurrent atmosphere formation

Nikolaou, Athanasia (2020)

Magma ocean is a crucial stage in the build-up of terrestrial planets. Its solidification and the accompanying outgassing of volatiles set the conditions for important processes that occur later or even simultane-ously, such as solid state mantle convection and atmospheric escape. In order to constrain the duration of a global scale magma ocean on Earth I have built and applied a 1D interior m...

KSPECTRUM_Htr16

Scheucher, Markus (2020-05-19)

KSPECTRUM_Htr16 computes high resolution molecular absorption spectra for gas mixtures under arbitrary thermodynamic conditions in a planetary atmosphere. This software package represents an update to KSPECTRUM 1.2 (original author: V. Eymet), downloaded under the Cecil License in 2018 from https://www.meso- star.com/pro jects/art/ kspectrum.html. The most important updates include: Utilization...