Free Astronomy Magazine March-April 2019

MARCH-APRIL 2019 run the risk of bringing life (essentially bac- teria) where we intend to go looking for it, thus potentially invalidating the research it- self. Nor can we expose our terrestrial bios- phere to extraterrestrial contamination, the consequences of which are not at all pre- dictable because we do not know how uni- versal and adaptable the immune systems of the involved organisms might be. Biolog- ical defense mechanisms evolve only when the threat becomes real and is recognized on the basis of some typical products of mi- crobial metabolism. Microbes belonging to an alien biosphere may not be recognized as a threat to terres- trial organisms, and the attacked organisms may have no defense to the alien microbes or their metabolic products. If the practice of planetary protection is mandatory within our own solar system, the same cannot be said about its applica- tion to other planetary systems, even if their exploration comes with similar ethical issues. At first sight, it seems a matter of a distant future − but it is not so, as there are projects that already aim to spread terres- A rtist concept of a wafersat approaching the potentially-habit- able exoplanet Proxima b. [PHL @ UPR Arecibo] The video below illustrates the Breakthrough Starshot project. [Breakthrough Starshot Initia- tives]