Life needs energy. On earth, bacteria, plants and animals take it easily from sunlight. But elsewhere, on planets far from a star, or without atmosphere and liquid water, things become much more complicated. Unless exploited the cosmic rays, energy particles from the open space that constantly bomb even the most remote corners of the universe. Usually they are considered incompatible with biological life, because they are ionizing radiation capable of damaging cells and tissues. But in the right conditions they could turn into the engine of a hypothetical alien ecosystem, at least according to the calculations of a team of researchers from New York University Abu Dhabi.
Harmful to life
On our planet, the cosmic rays are blocked almost completely by the magnetosphere (our planetary magnetic field) and the atmosphere. And it is good, because these very high energy particles can damage the DNA of our cells, causing tumors, genetic mutations, damage to the immune and cardiovascular system. The same applies more or less for each known living creature. And therefore, normally the planets without magnetic field and atmosphere that shield the surface with cosmic rays are considered uninhabitable.
Even in such places, however, there are places where you can escape the harmful effects of these particles. Mari and Oceani, for example, offer excellent protection, even better than that guaranteed by a gaseous atmosphere. And even better it makes the ground: cosmic rays can penetrate it at most for a few meters. And in doing so, they produce chemical reactions due to radiolisi, that is, the split of one or more chemical bonds of a molecule due to the effect of ionizing radiation.
An unexpected source of energy
On Earth there are bacteria such as Deinococcus Radiodurans, which to adapt to survive in really extreme environments have evolved the ability to use radiolisi products as a source of energy and nourishment. Starting from this awareness, the authors of the study recently published on the International Journal of Astrobiology, have asked themselves: is it possible that something similar also happens on cold and inhospitable planets such as Mars or the frozen moons of Jupiter and Saturn?
To find out, they used a computerized simulation to study how much energy can generate the impact of cosmic rays, affecting water or ice molecules in the subsoil of such a planet. The results confirmed their intuition: enough energy to support small microbial life forms such as the terrestrial Deinococcus. The most promising planet in this sense would be Encelado, the Luna di Saturna suspected of guarding an ocean of liquid water under its frozen surface. Followed by Mars, and therefore from the moon of Jupiter Europe.
Are the habitable planets more than expected?
“This discovery is destined to change the way we think of the places where life can exist,” explains Dimitra Atri, a Scientist of New York University Abu Dhabi who led the research. “Instead of looking only at hot and well -enlightened planets, now we can also consider cold and dark places, as long as they have some water under their surface and are exposed to cosmic rays. Life could therefore be able to survive in many more places than we ever imagined”.
For this reason, the authors of the study propose to update the concept of the area, the portion of space around a star in which the planets are considered potentially able to host life. In the past, it has always been calculated based on the possibility that a planet has liquid water on the surface, established according to the distance from its star. The proposal of researchers of New York University Abu Dhabi is to introduce a new concept: that of the radioiolitic area, in which all the planets fall with reserves of underground water that can receive energy from cosmic rays. Their calculations will be verified by other teams of scientists, and if possible, testing with field investigations (which is feasible, for example, on Mars, or on Europe, where in 2030 the Mission of the NASA European Clipper should arrive). If they were right, however, suddenly the chances of existing alien life forms somewhere in space would have become much more concrete.