What PROCESS experiment brought to astrochemistry, and more globally to exobiology?
One part of the sample was constituted of amino acids, essential molecules when it comes to understand the origin of life. They are the building blocks of all proteins and it is hard to imagine that a living organism could do without. These molecules can be brought to Earth by some meteorites or comets. Thanks to PROCESS experiment, the rate of deterioration of these molecules in space could be measured and it was found that ultraviolet radiation is the main cause. Associated with other irradiations carried out in laboratories as support, PROCESS also led to a better knowledge of the interactions between organic molecules and the mineral matter. Indeed, it can, depending on the ultraviolet radiation absorbed, protect the compounds significantly or not. Thus, the compounds imported to Earth by meteorites, micrometeorites and comets could somehow undergo a "selection" during their interplanetary journey, promoting on Earth the molecules the most resistant to space conditions.
Another set of samples was exposed under a filter recreating the conditions of photolysis on the surface of Mars. A few weeks before the arrival of the Mars rover Curiosity of MSL/NASA mission, which payload includes instruments dedicated to the research of organic matter on Mars, PROCESS provides some determinant information. Measurements of photochemical lifetime of some of the researched compounds (amino acids and carboxylic acids) indicate that their abundances should be too low to hope that we can detect these molecules on the surface if their only source in the Martian environment is a meteoritic contribution.
EXPOSE platform (circled in red) installed outside the International Space Station,
at about 350 km altitude. At this altitude, solar ultraviolet radiations are not filtered
as opposed to those that reach the surface of our planet after having crossed the atmosphere.
Credits: © NASA/ESA
Finally, a new kind of experiment were conducted with PROCESS: in addition to samples exposed as solid, an original experimental device has paved the way for a new type of molecules that have never before been sent into orbit for such experiments: samples in gaseous phase, simulating the evolution of planetary atmospheres under the action of solar radiation. For PROCESS, mixtures representative of Titan's atmosphere (molecular nitrogen (N2) and methane (CH4)) were prepared in the laboratory before being sent into orbit. The results brought back by PROCESS are consistent with what is known about the behavior of this type of gas mixture under the action of ultraviolet radiation. These conclusive measurements will therefore allow generalization of this type of samples for future campaigns of exposure in Earth orbit.
For more detailed information:
Hervé Cottin, Yuan Yong Guan, Audrey Noblet, Olivier Poch, Kafila Saiagh, Mégane Cloix, Frédérique Macari, Murielle Jérome, Patrice Coll, François Raulin, Fabien Stalport, Cyril Szopa, Marylène Bertrand, Annie Chabin, Frances Westall, Didier Chaput, René Demets, André Brack,
The PROCESS Experiment: An Astrochemistry Laboratory for Solid and Gaseous Organic Samples in Low-Earth Orbit,
Astrobiology. May 2012, 12(5): 412-425.
M. Bertrand, A. Chabin, A. Brack, H. Cottin, D. Chaput, F. Westall,
The PROCESS Experiment: Exposure of Amino Acids in the EXPOSE-E Experiment on the International Space Station and in Laboratory Simulations,
Astrobiology. May 2012, 12(5): 426-435.
Audrey Noblet, Fabien Stalport, Yuan Yong Guan, Olivier Poch, Patrice Coll, Cyril Szopa, Mégane Cloix, Frédérique Macari, François Raulin, Didier Chaput, Hervé Cottin,
The PROCESS Experiment: Amino and Carboxylic Acids Under Mars-Like Surface UV Radiation Conditions in Low-Earth Orbit,
Astrobiology. May 2012, 12(5): 436-444.
These three papers were published in Astrobiology Special Collection: The EXPOSE-E Mission.
Read also the article on ESA website