Exporting life to another planet: much more than a fantasy

There is a particular branch of biological studies which, after about a century of silence, has regained strength thanks to new knowledge acquired in the last 20-30 years. It is one of those sectors that most arouse the interest not only of scientists, but also of the general public, and therefore I think it might be interesting to mention it briefly. The idea that life can make interplanetary travelbeing disseminated from one planet to another – a theory called panspermia – is certainly not new: the first fragmentary hints come from perhaps the pre-Socratic Greek philosopher Anaxagoras, who lived between 500 and 428 BC Anaxagoras, in his cosmological reflections, mentions twice the “seeds” (in Greek, sperm) as part of the cosmos, although it does not directly clarify the meaning of the word; according to recent interpretations, these seeds are the seeds of life, which spread throughout the cosmos and take root on infinite worlds.

The German doctor Herman Richter he was the first to revive panspermia in the light of new considerations, and the first to call it that. In 1865, he called extraterrestrial life cozmozoa and suggested that panspermia was “consistent with opinions established in other fields of science; provides the cornerstone for Darwin’s bold edifice.” (remember that Darwin did not pronounce on the origin of life). Lord Kelvin he wrote in turn in 1871: “We must consider it probable in the highest degree that there are innumerable seed-bearing meteoric stones moving through space. If at present there were no life on this Earth, such a stone falling upon it might, by what we blindly call natural causes, cause it to become overgrown.”

The visions of scientists and thinkers of past centuries perhaps they sinned with too much optimism and a certain amount of naivety, colliding, in the twentieth century, with the observation of the very harsh and prohibitive conditions found in interplanetary space: lack of oxygen, temperature extremes, with very low peaks during a journey between planets and very high during the eventual impact of a meteorite that transports living beings , and then ionizing radiation from the sun, which destroys biological macromolecules, especially DNA, and high-intensity ultraviolet radiation, with the same deleterious effects. Nevertheless, recently a group of prominent scientists from MIT and Harvard spent a decade, and a fair amount of funding from NASA and other sources, to design and produce an instrument that could be sent to Mars and detect the presence of DNA on that planet or RNAto give basis to the speculation that life may have come to Earth from Mars or that, on the contrary, in the past, when conditions on Mars were much more similar to those of Earth, it had been colonized by terrestrial organisms.

What happened? First, they have accumulated the evidence of the exchange of meteorites between Mars and the Earth-Moon system: hundreds of impacts recorded on our planet correspond to objects coming from the red planet, and a meteorite of terrestrial origin has been found on the Moon, demonstrating the exchange of rocky material between these celestial bodies. Secondly, the microbiology of the last decades has definitively changed our conception of a supposed universal fragility of living organisms. The bacterium Deinococcus radiodurans he is able to withstand an acute dose of 5,000 grays, or 500,000 rads, of ionizing radiation with almost no loss of vitality, and an acute dose of 15,000 Gy with 37% vitality. Under these conditions, it has been found to withstand multi-year exposures in outer space, and is similarly intact in the presence of high-dose ultraviolet radiation. Pyrococcus furiosus it flowers at a temperature of 100 degrees centigrade, like many other species resistant to acids and to very low temperatures thanks to phenotypes resistant in the state of dormancy. A further problem is constituted by the prolonged time of a possible interplanetary journey, which can be very long before a body coming from a given planet impacts on another. However, in 2020, bacterial cells were found beneath the surface of the ocean floor that have survived for probably 100 million years.

Bearing in mind these characteristics of terrestrial living organisms, the survival of bacteria during an interplanetary journey is more than possible; finally, even survival from a meteorite impact has been shown to be possible, if bacteria such as those described were to lurk deep in its cracks and well below the surface. Once on a new planet, the phenomenal plasticity of bacteria in exploiting every source of energy for their metabolism is well known: sulphur, manganese, ammonia and other chemical compounds are just a few examples of what can fuel their life, not to mention of simple sunlight, on condition that there is a source of carbon (even gaseous) and a few other chemical elements and at least temporarily liquid water. These latter constraints are well overcome on Mars, where more alternatives of the “right ingredients” are present; and perhaps, even admitting that it has never been present on that planet, it is possible that we have brought microbial life there, given that in the sterile rooms of NASA, in prohibitive conditions created precisely to protect the components of the machines that we launch into space from contamination , colonies of specialized bacteria have been found, perhaps already arrived on Mars on one of the landers we sent you. In short: the likelihood that Anaxagoras and Lord Kelvin, along with countless other dreamers, were right after all, has never seemed higher.