The ISS is constantly evolving.

 

The ISS is constantly evolving

By 2011, the space station had accumulated more than 150 different components and fourteen pressurized modules, with astronauts clocking more than 1,000 hours in space, connecting all the pieces.

Five more modules were added in the following eleven years, with more modules already in the works.

The ISS provides a location in the relative safety of low Earth orbit to test spacecraft systems that will be required for long-duration missions to the Moon and Mars. This provides experience in operations, maintenance as well as repair and replacement activities on-orbit. This will help develop essential skills in operating spacecraft farther from Earth, reduce mission risks, and advance the capabilities of interplanetary spacecraft.^[13] Referring to the MARS-500 experiment, a crew isolation experiment conducted on Earth, ESA states that "Whereas the ISS is essential for answering questions concerning the possible impact of weightlessness, radiation and other space-specific factors, aspects such as the effect of long-term isolation and confinement can be more appropriately addressed via ground-based simulations".^[68] Sergey Krasnov, the head of human space flight programmes for Russia's space agency, Roscosmos, in 2011 suggested a "shorter version" of MARS-500 may be carried out on the ISS.^[69]

In 2009, noting the value of the partnership framework itself, Sergey Krasnov wrote, "When compared with partners acting separately, partners developing complementary abilities and resources could give us much more assurance of the success and safety of space exploration. The ISS is helping further advance near-Earth space exploration and realisation of prospective programmes of research and exploration of the Solar system, including the Moon and Mars."^[70] A crewed mission to Mars may be a multinational effort involving space agencies and countries outside the current ISS partnership. In 2010, ESA Director-General Jean-Jacques Dordain stated his agency was ready to propose to the other four partners that China, India and South Korea be invited to join the ISS partnership.^[71] NASA chief Charles Bolden stated in February 2011, "Any mission to Mars is likely to be a global effort".^[72] Currently, US federal legislation prevents NASA co-operation with China on space projects.^[73]