June 11, 2012

Results of the PROCESS experiment on board EXPOSE-E

The PROCESS experiment (PRebiotic Organic ChEmistry on Space Station) on board EXPOSE consisted in expose samples mainly composed of organic molecules during 18 months in 2008 and 2009, outside the International Space Station.

The results of this experiment were published in three articles of the Astrobiology magazine which issued on this occasion an issue fully dedicated to the results of EXPOSE-E on which the French chemistry experiment cohabited with other projects more focused on biology.

PROCESS measured the deterioration speed of amino-acids

Part of the samples was composed of amino-acids, incontrovertible molecules when trying to understand the life emergence because they are the elementary building blocks of every protein of which a living organism cannot do without. Those molecules can be brought on Earth by some meteorites or comets. Thanks to the PROCESS experiment, the deterioration speed of those molecules in space have been measured and it appeared that the UV radiations is main cause of deterioration.

With other irradiations performed in the laboratory as background material, PROCESS allowed scientists to better understand the interactions between organic molecules and mineral matter. In fact, the latter can, depending on the UV radiation absorbed, protect the compounds significantly or not. So the compounds brought on Earth by meteorites, micrometeorites and comets could be in some ways selected during their interplanetary trips, favouring on Earth the more space condition-resistant molecules.

The carboxylic and amino acids' life time is too short on Mars

Another set of samples was exposed under a filter which simulated the photolysis conditions at the Martian surface. In the run-up to the rover Curiosity (mission MSL/NASA) landing on Mars, on board of which part of the instruments are dedicated to she research of organic matter on the red planet, PROCESS brings decisive elements. Photochemical life time measurements of some of the sought compounds (amino-acids and carboxylic acids) indicate that they are too short to expect finding those molecules at the surface if their only source in the Martian environment is a meteorite input.

Titan's atmosphere also simulated by PROCESS

Finally, PROCESS was the occasion of a large experimental world-first: more than only solid samples, an original experimental device opened the path to a new type of molecules which were never sent into orbit for this type of experiment: gaseous state samples to simulate the impact of the solar radiations on the planetary atmosphere evolution. For PROCESS, Titan's atmosphere-like mix (molecular nitrogen (N2) and methane (CH4)) were prepared in the laboratory before being sent into orbit. The results brought by PROCESS are consistent with what we already knew about the impact of UV radiations on the behaviour of this type of gaseous mix. Those successful measurements will thus make the generalisation of this type of samples possible for the next Earth-orbiting exposure expeditions.

EXPOSE platform (circled in red) installed on the outside of the ISS At approximately 350 km altitude, the solar UV radiations are not filtered unlike those that reach the Earth's surface through the atmosphere © NASA/ESA

Indeed, when the AMINO experiment's samples and results are still being analysed and interpreted, next exposure expeditions on the International Space Station are already being planned.

First of all, the PSS experiment which would reach the Earth orbit in late 2013. LISA is again leading the experiment, but this time with an international astrochemist team including:

  • the CBM;
  • LATMOS
  • the observatory of Bordeaux, France;
  • the university of Montpellier, France;
  • the university of Leiden, Netherlands;
  • observatory of Catane, Italy;
  • NASA AMES center, United-States.

Beyond those experiments, new exposure platforms are being studied: they will feature analysis instruments which will be able to measure the sample evolution in real time and send the data to the scientists on the ground: harder to conceive but easier to exploit because it will not be necessary anymore to bring back the samples on Earth to analyse them.

Articles references

Bertrand, M., Chabin, A., Brack, A., Cottin, H., Chaput, D., Westall, F. (2012), The PROCESS Experiment: Exposure of amino acids in the EXPOSE-E experiment on the ISS and in laboratory simulations, Astrobiology, 12, 426-435.

Cottin, H., Noblet, A., Guan, Y.Y., Poch, O., Saiagh, K., Cloix, M., Macari, F., Jérome, M., Coll, P., Raulin, F., Stalport, F., Szopa, C., Bertrand, M., Chabin, A., Westall, F., Chaput, D., Demets, R., Brack, A. (2012), The PROCESS experiment: an astrochemistry laboratory for solid and gaseous organic samples in low Earth orbit, Astrobiology, 12, 412-425.

Noblet, A., Guan, Y.Y., Stalport, F., Poch, O., Coll, P., Szopa, C., Cloix, M., Macari, F., Raulin, F., Chaput, D., Cottin, H. (2012), The PROCESS experiment: Amino and carboxylic acids under Mars like surface UV radiation conditions in low Earth orbit, Astrobiology, 12, 436-444.

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