Doctoral Researcher Chang-hyun Maeng of the Graduate School of Life Science along with Professor Tomomichi Fujita of the Faculty of Science at Hokkaido University, Professor Yuji Hiwatashi and Graduate Student Keita Nakamura of Miyagi University, Assistant Professor Osamu Matsuda and Professor Atsushi Kume of Kyushu University, Professor Hajime Mita of Fukuoka Institute of Technology, Lecturer Kaori Tomita-Yokotani of the Faculty of Life and Environmental Sciences at the University of Tsukuba (at the time of the research), and Associate Professor Shin-ichi Yokobori and Professor Emeritus Akihiko Yamagishi of Tokyo University of Pharmacy and Life Sciences announced their research group has demonstrated that spores of the model moss plant Physcomitrium patens can survive for extended periods in outer space. Using the external section of the International Space Station (ISS), sporophytes were exposed to outer space for approximately 9 months. Germination was confirmed in germination tests conducted on the ground. This may lead to the development of sustainable space ecosystems and biological life support systems. The results were published in iScience on November 21.
Right: A reddish-brown, rounded capsule (sporangium) is visible at the top center of a single thallus. This capsule contains numerous spores internally. Mature capsules were collected individually from the thallus to form spore samples, which were then subjected to space exposure experiments on the International Space Station's exposed section.
Provided by Chang-hyun Maeng, Hokkaido University
To achieve space habitation, it is necessary to construct an ecosystem using organisms that can survive in the harsh and extreme environments of space. Plants are essential for life support, including oxygen supply and carbon fixation, but whether they could survive in outer space was unknown.
Bryophytes are plants that first colonized land approximately 500 million years ago and have evolved high tolerance to harsh environments such as drought, ultraviolet radiation, and extreme temperature changes.
The research group has positioned mosses as ideal model organisms for evaluating survival capabilities in extraterrestrial environments, focused on its potential for space applications. However, previous space exposure experiments primarily targeted seed plants, with almost no data available on bryophytes.
Therefore, the researcher compared tolerance under extreme environmental conditions using three types of tissues of P. patens (protonema) and three types of stress-tolerant cells (spores).
Each tissue was subjected to harsh conditions such as ultraviolet radiation (UV-C), extreme low temperature (-80℃), high temperature (55℃), and vacuum, and their viability was evaluated. The spores showed particularly high tolerance compared with other tissues. Based on these findings, space exposure experiments were then conducted using spores.
The space exposure experiment was conducted as part of Japan's "Tanpopo 4" mission. Dried sporophytes of P. patens were fixed on sterilized aluminum plates and mounted on ExBAS, the Exposed Experiment Bracket Attached on i-SEEP (IVA-replaceable Small Exposed Experiment Platform). This was placed on the extravehicular experimental platform developed by JAXA in the Japanese Experiment Module "Kibo" of the ISS. For approximately 9 months, they were exposed to the space environment, which includes vacuum, microgravity, space radiation, ultraviolet radiation, and extreme temperature fluctuations.
After the exposure period ended, samples were retrieved and transported to the ground via return capsule. These were then analyzed with a focus on germination rates. In parallel, control experiments were conducted on the ground replicating similar conditions such as vacuum, ultraviolet radiation, and temperature changes, and the effects of the space environment on moss spores were comparatively evaluated.
As a result, it was confirmed that P. patens spores can survive for extended periods even in actual space environments. More than 80% of the space-exposed spores germinated normally on the ground. This revealed for the first time that spores, the "seeds of moss," can survive in actual outer space.
In the future, the group will work on elucidating moss's tolerance to space radiation and long-term survival mechanisms, building upon the data obtained.
Fujita commented: "From observing the moss that survived in space, I felt the limitless possibilities of the systems that life possesses. Taking on the extreme environment of space also provides an opportunity to reconsider the future of all life living on the single 'point' that is Earth. By challenging the use of the most severe space environment, I hope to contribute to the regeneration of Earth's environment."
Journal Information
Publication: iScience
Title: Extreme environmental tolerance and space survivability of the moss, Physcomitrium patens
DOI: 10.1016/j.isci.2025.113827
This article has been translated by JST with permission from The Science News Ltd. (https://sci-news.co.jp/). Unauthorized reproduction of the article and photographs is prohibited.