The McMurdo Dry Valleys, located in the Antarctic Victoria Land, are considered to be the most similar earthly equivalent to Mars. They make up one of the driest and most hostile environments on our planet, where strong winds scour away even snow and ice. Only so-called cryptoendolithic microorganisms—capable of surviving in cracks in rocks—and certain lichens can withstand such harsh conditions.
A few years ago a team of European researchers traveled to these remote valleys to collect samples of two species of cryptoendolithic fungi: Cryomyces antarcticus and Cryomyces minteri. The aim was to send them to the International Space Station (ISS) for them to be subjected to Martian conditions and space to observe their responses.
The tiny fungi were placed in cells (1.4 centimeters in diameter) on a platform for experiments known as EXPOSE-E, developed by the European Space Agency to withstand extreme environments. The platform was sent in the Space Shuttle Atlantis to the ISS.
For 18 months half of the Antarctic fungi were exposed to Mars-like conditions. More specifically, they were placed in an atmosphere with 95% CO2, 1.6% argon, 0.15% oxygen, 2.7% nitrogen and 370 parts per million of H2O; and a pressure of 1,000 pascals. Through optical filters, some of the samples were subjected to ultraviolet radiation as if on Mars (higher than 200 nanometers) and others to lower radiation, including separate control samples.
“The most relevant outcome was that more than 60% of the cells of the endolithic communities studied remained intact after ‘exposure to Mars,’ or rather, the stability of their cellular DNA was still high,” says Rosa de la Torre Noetzel from Spain’s National Institute of Aerospace Technology (INTA), co-researcher on the project.
The scientist explains that this work, published in the journal Astrobiology, forms part of an experiment known as the Lichens and Fungi Experiment (LIFE), “with which we have studied the fate or destiny of various communities of lithic organisms during a long-term voyage into space on the EXPOSE-E platform.”
“The results help to assess the survival ability and long-term stability of microorganisms and bioindicators on the surface of Mars, information which becomes fundamental and relevant for future experiments centered around the search for life on the red planet,” says De la Torre.
Researchers from the LIFE experiment, coordinated from Italy by Professor Silvano Onofri from the University of Tuscany, have also studied two species of lichens (Rhizocarpon geographicum and Xanthoria elegans) which can withstand extreme high-mountain environments. These were gathered from the Sierra de Gredos (Avila, Spain) and the Alps (Austria), with half of the specimens also being exposed to Martian conditions.
Another group of samples (both lichens and fungi) was subjected to an extreme space environment (with temperature fluctuations of between -21.5 and +59.6 °C, galactic-cosmic radiation of up to 190 megagrays, and a vacuum of between 10^-7 to 10^-4 pascals). The effect of the impact of ultraviolet extraterrestrial radiation on half of the samples was also examined.
After the year-and-a-half-long voyage, the two species of lichens exposed to Martian conditions showed double the metabolic activity of those that had been subjected to space conditions, even reaching 80% more in the case of the species Xanthoria elegans.