ISS4Mars: Using Low Earth Orbit Stations to Enable Human Exploration of Mars

ISS4Mars is a global initiative to use the International Space Station (ISS) as an analog of human missions to Mars. The ISS provides a spaceflight platform that can be used to test different operational scenarios that mimic the autonomy, duration, and communication delays expected during a Mars mission. Studies conducted on the ISS can assess the risks that astronauts will encounter during a Mars mission and the integrated technologies and countermeasures required to keep them safe. The idea of using the ISS as a testbed for a Mars Mission was first presented in Prague at the Humans in Space Symposium in 2015. After two international workshops, one held in Rome in 2018, and one held remotely in 2020–2021, space agencies agreed to implement a stepwise approach, starting with simple use cases. Five use cases were identified, and the international Multilateral Human Research Panel for Exploration (MHRPE) added more details to the use cases, including considerations for operational feasibility, and each agency’s desired role in preparing for potential implementation. The MHRPE then selected four of these use cases and one space agency to lead the development of each implementation plan. These four use cases are described in this paper, focusing on which facets of a Mars mission they will survey and the operational challenges of implementing them on the ISS. The following practices regarding the ISS4Mars initiative are discussed: (1) scenarios, technologies, and countermeasures must be first tested in terrestrial analogs of spaceflight, parabolic flight, or suborbital and shorter duration orbital spaceflight; (2) ISS4Mars studies should not affect other research being conducted on the ISS, however, they should represent some of the highest priority research to enable human exploration; (3) commercial low Earth orbit (LEO) stations should be considered for implementing these studies post-ISS; (4) new international collaborative methods and partnerships should be pursued, if needed, to implement these studies on the ISS. These use cases are a first step toward using LEO and lunar platforms as analogs to prepare for future Mars missions. Ultimately, many, if not all, Mars mission operations will be tested in advance to optimize integration and synergy. This testing will require extensive planning, potentially involving scaling up single use cases to a multiple use case approach. By safely working close to Earth using the ISS4Mars approach, international agencies and commercial partners can develop the vehicles and tools needed to enable human exploration of Mars.