^1,2Matthew J. Genge,²Natasha Almeida,³Matthias Van Ginneken,⁴Lewis Pinault,⁵Louisa J. Preston,³Penelope J. Wozniakiewicz,^6,7Hajime Yano
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14288]
¹Department of Earth Science and Engineering, Imperial College London, London, UK
²Planetary Materials Group, Natural History Museum, London, UK
³Centre for Astrophysics and Planetary Science, Dept. Physics and Astronomy, University of Kent, Canterbury, Kent, UK
⁴Department of Earth and Planetary Sciences, Birkbeck College, London, UK
⁵Department of Space and Climate Physics, Mullard Space Science Laboratory, University College London, Surrey, UK
⁶Department of Interdisciplinary Space Science, Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), Sagamihara, Kanagawa, Japan
⁷Space and Astronautical Science, Graduate Institute for Advanced Studies, SOKENDAI, Sagamihara, Kanagawa, Japan
Published by arrangement with John Wiley & Sons

The presence of microorganisms within meteorites has been used as evidence for extraterrestrial life, however, the potential for terrestrial contamination makes their interpretation highly controversial. Here, we report the discovery of rods and filaments of organic matter, which are interpreted as filamentous microorganisms, on a space-returned sample from 162173 Ryugu recovered by the Hayabusa 2 mission. The observed carbonaceous filaments have sizes and morphologies consistent with microorganisms and are spatially associated with indigenous organic matter. The abundance of filaments changed with time and suggests the growth and decline of a prokaryote population with a generation time of 5.2 days. The population statistics indicate an extant microbial community originating through terrestrial contamination. The discovery emphasizes that terrestrial biota can rapidly colonize extraterrestrial specimens even given contamination control precautions. The colonization of a space-returned sample emphasizes that extraterrestrial organic matter can provide a suitable source of metabolic energy for heterotrophic organisms on Earth and other planets.