| 1. |
- Lammer, H., et al.
(författare)
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Exoplanet status report: Observation, characterization and evolution of exoplanets and their host stars
- 2010
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Ingår i: Solar System Research. - 1608-3423 .- 0038-0946. ; 44:4, s. 290-310
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Tidskriftsartikel (refereegranskat)abstract
- After the discovery of more than 400 planets beyond our Solar System, the characterization of exoplanets as well as their host stars can be considered as one of the fastest growing fields in space science during the past decade. The characterization of exoplanets can only be carried out in a well coordinated interdisciplinary way which connects planetary science, solar/stellar physics and astrophysics. We present a status report on the characterization of exoplanets and their host stars by reviewing the relevant space- and ground-based projects. One finds that the previous strategy changed from space mission concepts which were designed to search, find and characterize Earth-like rocky exoplanets to: A statistical study of planetary objects in order to get information about their abundance, an identification of potential target and finally its analysis. Spectral analysis of exoplanets is mandatory, particularly to identify bio-signatures on Earth-like planets. Direct characterization of exoplanets should be done by spectroscopy, both in the visible and in the infrared spectral range. The way leading to the direct detection and characterization of exoplanets is then paved by several questions, either concerning the pre-required science or the associated observational strategy.
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| 2. |
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| 3. |
- Lammer, H., et al.
(författare)
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Geophysical and Atmospheric Evolution of Habitable Planets
- 2010
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Ingår i: Astrobiology. - : Mary Ann Liebert Inc. - 1531-1074 .- 1557-8070. ; 10:1, s. 45-68
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Tidskriftsartikel (refereegranskat)abstract
- The evolution of Earth-like habitable planets is a complex process that depends on the geodynamical and geophysical environments. In particular, it is necessary that plate tectonics remain active over billions of years. These geophysically active environments are strongly coupled to a planet's host star parameters, such as mass, luminosity and activity, orbit location of the habitable zone, and the planet's initial water inventory. Depending on the host star's radiation and particle flux evolution, the composition in the thermosphere, and the availability of an active magnetic dynamo, the atmospheres of Earth-like planets within their habitable zones are differently affected due to thermal and nonthermal escape processes. For some planets, strong atmospheric escape could even effect the stability of the atmosphere.
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| 4. |
- Abrevaya, Ximena C., et al.
(författare)
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Protective Effects of Halite to Vacuum and Vacuum-Ultraviolet Radiation : A Potential Scenario during a Young Sun Superflare
- 2023
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Ingår i: Astrobiology. - : Mary Ann Liebert Inc. - 1531-1074 .- 1557-8070. ; 23:3, s. 245-268
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Tidskriftsartikel (refereegranskat)abstract
- Halite (NaCl mineral) has exhibited the potential to preserve microorganisms for millions of years on Earth. This mineral was also identified on Mars and in meteorites. In this study, we investigated the potential of halite crystals to protect microbial life-forms on the surface of an airless body (e.g., meteorite), for instance, during a lithopanspermia process (interplanetary travel step) in the early Solar System. To investigate the effect of the radiation of the young Sun on microorganisms, we performed extensive simulation experiments by employing a synchrotron facility. We focused on two exposure conditions: vacuum (low Earth orbit, 10-4 Pa) and vacuum-ultraviolet (VUV) radiation (range 57.6-124 nm, flux 7.14 W/m2), with the latter representing an extreme scenario with high VUV fluxes comparable to the amount of radiation of a stellar superflare from the young Sun. The stellar VUV parameters were estimated by using the very well-studied solar analog of the young Sun, κ1 Cet. To evaluate the protective effects of halite, we entrapped a halophilic archaeon (Haloferax volcanii) and a non-halophilic bacterium (Deinococcus radiodurans) in laboratory-grown halite. Control groups were cells entrapped in salt crystals (mixtures of different salts and NaCl) and non-trapped (naked) cells, respectively. All groups were exposed either to vacuum alone or to vacuum plus VUV. Our results demonstrate that halite can serve as protection against vacuum and VUV radiation, regardless of the type of microorganism. In addition, we found that the protection is higher than provided by crystals obtained from mixtures of salts. This extends the protective effects of halite documented in previous studies and reinforces the possibility to consider the crystals of this mineral as potential preservation structures in airless bodies or as vehicles for the interplanetary transfer of microorganisms.
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| 5. |
- Kaltenegger, L., et al.
(författare)
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Stellar Aspects of Habitability-Characterizing Target Stars for Terrestrial Planet-Finding Missions
- 2010
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Ingår i: Astrobiology. - : Mary Ann Liebert Inc. - 1531-1074 .- 1557-8070. ; 10:1, s. 103-112
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Tidskriftsartikel (refereegranskat)abstract
- We present and discuss the criteria for selecting potential target stars suitable for the search for Earth-like planets, with a special emphasis on the stellar aspects of habitability. Missions that search for terrestrial exoplanets will explore the presence and habitability of Earth-like exoplanets around several hundred nearby stars, mainly F, G, K, and M stars. The evaluation of the list of potential target systems is essential in order to develop mission concepts for a search for terrestrial exoplanets. Using the Darwin All Sky Star Catalogue (DASSC), we discuss the selection criteria, configuration-dependent subcatalogues, and the implication of stellar activity for habitability.
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