There were three EXPOSE experiments completed between 2008 and 2015: EXPOSE-E, EXPOSE-R and EXPOSE-R2.
The EXPOSE-E was launched on 7 February 2008 on board the Space Shuttle Atlantis and was mounted on the ISS European module Columbus to the European Technology Exposure Facility (EuTEF). EXPOSE-R was launched to the ISS on 26 November 2008 from Baikonur Cosmodrome in Kazakhstan on board of a Progress capsule and was mounted on the ISS Russian module Zevzda. EXPOSE-E provided accommodation in three exposure trays for a variety of astrobiological test samples that were exposed to selected space conditions: either to space vacuum, solar electromagnetic radiation at >110 nm and cosmic radiation (trays 1 and 3) or to simulated Martian surface conditions (tray 2). The different experiments consisted in exposing solid molecules, gas mixtures or biological samples to the solar ultraviolet (UV) radiation, cosmic rays, vacuum and temperature fluctuations of outer space as the ISS repeatedly passed between areas of direct sunlight and the cold darkness of Earth's shadow.
At the end of the exposition period, EXPOSE-E was brought back to the ground in September 2009 as part of the Space Shuttle Discovery mission STS-128. EXPOSE-R was brought back in 2011 by a Soyuz spacecraft. From the landing site in Kazakhstan, the trays were returned via Moscow and distributed to scientists for further analysis in their laboratories. EXPOSE-R2 was launched on 24 July 2014, exposure was finished in April 2015, and was returned to Earth in early 2016 where it is still undergoing analyses.