Expose-R2 Photochemistry on the Space Station

By Richard Quinn - Senior Research Scientist 

After 18 months mounted externally on the International Space Station Zvezda module, the European Space Agency Expose-R2 Photochemistry on the Space Station (PSS) experiment was retrieved by cosmonauts during a February spacewalk.  The PSS experiment investigated the evolution of organic compounds upon exposure to space radiation.

Led by University of Paris-Est Créteil investigator Herve Cottin, the PSS experiment involved a team of 30 Co-Investigators from 11 laboratories in the Netherlands, Italy, France, and the USA – including Richard Quinn of the SETI Institute.

Explained by Cottin, “Expose is nothing less than a little chemistry box to help us better understand chemical reactions in space. If a molecule survives 18 months in space then it could come to Earth from space.  If a molecule has changed after its 18-month voyage then we know that space travel filters our observations on Earth and a chemical might have formed from a different configuration.”

The PSS samples returned to Earth in a Soyuz-44 capsule along with Astronaut Scott Kelly returning after his year in space and landed in Kazakhstan on March 2, 2016.  The landing was carried live on NASA television and video of the PSS removal taken during the February spacewalk is also available on its website.

According to the French Space Agency website the samples were then sent to Cologne, Germany, and then to Créteil.  They will be extracted from the sample carriers and referenced before being sent again to other European cities and their laboratories of origin. They will be analyzed in the same conditions as before their departure and compared to the samples that stayed on Earth.

All tests are expected to be completed by October 2016. 

Figure 1 Expose-R2 and the PSS experiment imaged during a February 2016 EVA (Image from NASA/ESA)