Planet Formation and Panspermia. Группа авторов
Читать онлайн книгу.
the Solar System went through a significant radial displacement from the inner galactic disk, since its formation [2.40]. Therefore, unless the age and history of planetary systems are known to sufficient accuracy that they can be connected to the dynamical properties of the Galaxy, any conclusion on the occurrence of panspermia drawn from the detection of correlated biosignatures would be weakened. This reinforces the need for embedding the study of planetary habitability, and the interpretation of future searches for life beyond Earth, in the wider galactic context.
2.4 Conclusions
I have briefly outlined some of the reasons that should suggest a careful examination of the feasibility of interstellar panspermia. If transfer of microscopic life across stellar systems has been an active mechanism over the course of galactic history, the implications cannot be overemphasized. Just to name the most obvious repercussion: if the exchange of dust and rocks had a role in disseminating not only biological building blocks but also living organisms across the Galaxy, the whole question of the typical timescale of abiogenesis would have to be completely reconsidered (and, therefore, prior assumptions on the frequency of life beyond Earth should be changed accordingly). Also, while the detection of life outside the Solar System would be a momentous discovery, the mere possibility that its origin and distribution can be correlated among nearby stellar systems would drastically alter the broader consequences of such a finding.
For this reason, more attention should be given in the future to the possibility of lithopanspermia as a viable mechanism over interstellar distances. Ideally, one would want to have strong reasons to either admit or refute the possibility of interstellar panspermia before evaluating the results of future observations, so as to choose the right prior when interpreting possible biosignatures detections. From a theoretical point of view, this should imply a careful examination of effective dynamical routes (and of travel timescales) for the transfer of life-carrying rocks across space, including various factors that have been neglected in previous studies, such as the mixing of stellar orbits, or the enhanced capture cross-section due to inhomogeneities in the stellar distribution. Also, as mentioned previously, the result of such analyses should inform the construction of future models of the GHZ, where the interstellar transfer of life should be included as an additional process, in competition with catastrophic astrophysical events.
In parallel with such theoretical work, independent experimental studies would be crucial to assess the feasibility of the various processes involved. This should include, for example, continuing and expanding the investigation of the survivability of organisms in deep space, conducting in vivo experiments of hypervelocity impacts, and examining pristine samples of rocks from the early epochs of the Solar System. There are also good chances of observing more interstellar asteroids in the Solar System, which would result in refined estimates of the amount of material that can be transferred between stars. This would also open the exciting prospect of investigating the composition of rocks of extrasolar provenance, either remotely, through spectroscopic studies, or, in the more distant future, in situ, with dedicated space probes. All in all, evaluating the plausibility of interstellar panspermia should be one of the top priorities of both theoretical and experimental astrobiology in the near future.
References
[2.1] Adams, F.C., Hollenbach, D., Laughlin, G., Gorti, U., Photoevaporation of Circumstellar Disks Due to External Far-Ultraviolet Radiation in Stellar Aggregates. Astrophys. J., 611, 360–379, 2004.
[2.2] Adams, F.C. and Spergel, D.N., Lithospanspermia in Star-Forming clusters. Astrobiology, 5, 497–514, 2005.
[2.3] Arrhenius, S., Panspermy: the transmission of life from star to star. Sci. Am., 9, 196, 1907.
[2.4] Balbi, A. and Tombesi, F., The habitability of the Milky Way during the active phase of its central supermassive black hole. Sci. Rep., 7, 1, #16626, 2017.
[2.5] Balbi, A. and Grimaldi, C., Quantifying the information impact of future searches for exoplanetary biosignatures. Proc. Natl. Acad. Sci., 117, 35, 21031–21036, 2020.
[2.6] Balbi, A., Hami, M., Kovačević, A., The Habitability of the Galactic Bulge. Life, 10, 8, 132, 2020.
[2.7] Belbruno, E., Moro-Martín, A., Malhotra, R., Savransky, D., Chaotic Exchange of Solid Material Between Planetary Systems: Implications for Lithopanspermia. Astrobiology, 12, 754–774, 2012.
[2.8] Chen, H., Forbes, J.C., Loeb, A., Habitable Evaporated Cores and the Occurrence of Panspermia Near the Galactic Center. Astrophys. J. Lett., 855, 1, L1, 2018.
[2.9] Dick, S.J., The Biological Universe: The Twentieth-Century Extraterrestrial Life Debate and the Limits of Science, Cambridge University Press, Cambridge, 1996.
[2.10] Đošović, V., Vukotić, B., Ćirković, M.M., Advanced aspects of Galactic habitability. Astron. Astrophys., 625, A98, 2019.
[2.11] Forgan, D., Dayal, P., Cockell, C., Libeskind, N., Evaluating galactic habitability using high-resolution cosmological simulations of galaxy formation. Int. J. Astrobiology, 16, 1, 60–73, 2017.
[2.12] Fujii, Y., Angerhausen, D., Deitrick, R. et al., Exoplanet Biosignatures: Observational Prospects. Astrobiology, 18, 739, 2018.
[2.13] Ginsburg, I., Lingam, M., Loeb, A., Galactic Panspermia. Astrophys. J., 868, 1, L12, 2018.
[2.14] Gonzalez, G., Brownlee, D., Ward, P., The Galactic Habitable Zone: Galactic Chemical Evolution. Icarus, 152, 185–200, 2001.
[2.15] Gowanlock, M.G., Patton, D.R., McConnell, S.M., A model of habitability within the Milky Way galaxy. Astrobiology, 11, 855–873, 2011.
[2.16] Gowanlock, M.G. and Morrison, I.S., The Habitability of Our Evolving Galaxy, in: Habitability of the Universe Before Earth, R. Gordon and A.A. Sharov (Eds.), 2018, series: Astrobiology: Exploring Life on Earth and Beyond, P. H. Rampelotto, J. Seckbach, R. Gordon (Eds.), Elsevier B.V., Amsterdam, 149.
[2.17] Grenfell, J.L., A review of exoplanetary biosignatures. Phys. Rep., 713, 1–17, 2017.
[2.18] Horneck, G., Stöffler, D., Ott, S., Hornemann, U., Cockell, C.S., Moeller, R., Meyer, C., de Vera, J.-P., Fritz, J., Schade, S., Artemieva, N.A., Microbial rock inhabitants survive hypervelocity impacts on mars-like host planets: First phase of lithopanspermia experimentally tested. Astrobiology, 8, 1, 17–44, 2008.
[2.19] Horneck, G., Klaus, D.M., Mancinelli, R.L., Space Microbiology, Microbiology and Molecular Biology Reviews. Am. Soc. Microbiol., 74, 1, 121–156, 2010.
[2.20] Krijt, S., Bowling, T.J., Lyons, R.J., Ciesla, F.J., Fast Litho-panspermia in the Habitable Zone of the TRAPPIST-1 System. Astrophys. J., 839, 2, #L21, 2017.
[2.21] Lin, H.W. and Loeb, A., Statistical signatures of panspermia in exoplanet surveys. Astrophys. J. Lett., 810, 1, #L3, 2015.
[2.22] Lineweaver, C.H., Fenner, Y., Gibson, B.K., The Galactic Habitable Zone and the Age Distribution of Complex Life in the Milky Way. Science, 303, 5654, 59–62, 2004.
[2.23] Lingam, M. and Loeb, A., Enhanced interplanetary panspermia in the TRAPPIST-1 system. Proc. Natl. Acad. Sci. U.S.A., 114, 26, 6689–6693, 2017.
[2.24] Lingam, M. and Loeb, A., Implications of Captured Interstellar Objects for Panspermia and Extraterrestrial Life. Astron. J., 156, 5, 193, 2018.
[2.25] Lingam, M., Ginsburg, I., Bialy, S., Active Galactic Nuclei: Boon or Bane for Biota? Astrophys. J., 877, 1, 62, 2019.
[2.26] Madhusudhan, N., Exoplanetary Atmospheres: Key Insights, Challenges, and Prospects. Annu. Rev. Astron. Astrophys., 57, 617, 2019.
[2.27] Meech, K.J., Weryk, R., Micheli, M., Kleyna, J.T., Hainaut, O.R., Jedicke, R., Wainscoat, R.J., Chambers, K.C., Keane, J.V., Petric, A., Denneau, L., Magnier, E., Berger, T., Huber, M.E., Flewelling, H., Waters, C., SchunovaLilly, E.,