Free Astronomy Magazine July-August 2018

27 JULY-AUGUST 2018 ASTROBIOLOGY could support life, is extremely interesting. We must stress that, although organic mole- cules are central to all life, they are not nec- essarily indicators of life; in fact, they can also be produced by non-biological processes. Regardless of their origin, those organic com- pounds keep track of the processes and con- ditions present on the young Mars, and will, therefore, be useful for deepening our knowl- edge about the birth and evolution of that planet. This discovery by Curiosity is also a good omen for all the automatic missions al- ready started or in preparation, which all have as a goal the search for traces of life on the red planet. In the absence of being able to identify organic compounds, those mis- sions could likely not find anything. As the title of this article notes, the NASA rover has also made another important dis- covery thanks to the accumulation of years of analysis of the martian atmosphere. The discovery concerns methane, the simplest or- ganic molecule. For some years now, we’ve known that this gas is present in the martian atmosphere and is revealed on a regional scale in the form of large and unpredictable plumes occurring through unknown processes. If not a more-or- less constant supply, methane can remain in the atmosphere of Mars for a few centuries at most; therefore, if we still observe it today, this means that there is a mechanism that can renew it continuously − or at least periodi- cally. At the base of that mechanism, there could be essentially chemical and/or biologi- cal processes. On Earth, life forms produce more methane than abiotic reactions, and the same thing could happen on Mars. So far, however, the dynamics of the martian methane seemed not very compatible with possible biological activities. This situation could substantially change in light of a second article, also published in Science on June 8 th (first author Christopher R. Webster, NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California), in which it is shown that there is a seasonal variation in the abundance of atmospheric methane. The researchers reached this conclusion by an- alyzing the data collected over 5 years by the Tunable Laser Spectrometer, an instrument of SAM. Every summer, the methane concentra-