JAXA Completes Japan’s 1st Clean Room for Assembling Spacecraft Under Planetary Protection Standards

The Yomiuri Shimbun

2:00 JST, April 28, 2026

A first-of-its-kind clean room in Japan where space probes can be assembled while being sterilized has been completed in Sagamihara, Kanagawa Prefecture.

Its purpose is planetary protection, the practice of preventing Earth’s microorganisms from contaminating other celestial bodies. The Japan Aerospace Exploration Agency (JAXA) plans to use the facility to manufacture a probe it hopes to land on Mars around 2030. Operations are scheduled to begin this autumn.

Planetary protection is required of countries that have ratified the Outer Space Treaty. Some bacteria can enter a dormant state known as an endospore, enabling them to withstand the extreme cold and heat, as well as the dryness, of outer space. For that reason, the Committee on Space Research (COSPAR), an international organization of scientists, sets upper limits on the number of endospores allowed on spacecraft involved in landing missions to celestial bodies where life may exist.

The planetary protection clean room built on the JAXA Sagamihara campus covers about 43 square meters and includes an approximately 13-square-meter assembly room under sterilization control. Inside the room, which is designed to prevent outside air from entering, workers disinfect spacecraft components using heat, alcohol and ultraviolet light, then carry out spacecraft assembly and endospore-count inspections.

COSPAR has established upper limits on endospore counts for probes involved in missions such as Mars landings, and JAXA aims to meet those requirements in the production of Japan’s first Mars landing probe.

At the same time, the agency is developing operating procedures for the clean room and drafting transportation plans for moving spacecraft to launch sites while keeping bacterial levels reduced. In the future, it also hopes to build a larger facility capable of assembling large-scale probes.

The possible existence of extraterrestrial life has been pointed to on Mars; Europa, a moon of Jupiter; and Enceladus, a moon of Saturn. In its space technology strategy, the Cabinet Office has said it intends to build domestic planetary protection technologies and systems in support of the search for life in space.

“We want to strengthen Japan’s technological capabilities and contribute to the search for, and discovery of, life on Mars and other celestial bodies,” said Shunta Kimura, an associate professor at JAXA’s Institute of Space and Astronautical Science.