The surface of Venus is too hot for any life imaginable, but high in the atmospheric conditions are not so extreme, and the updrafts are quite capable of keeping local microbes from falling down.
Venus, with its dense, acidic atmosphere and high temperatures, is rarely seen as the home of possible life. However, high above the surface, some microbes are quite capable of surviving and retaining without sinking into the most dangerous lower layers. Such a mechanism was recently proposed by scientists led by Sara Seager, an astrobiologist at the Massachusetts Institute of Technology (MIT), who previously demonstrated the possibility of storing microbes in the unusual atmospheres of distant exoplanets.
In a new article published in the journal Astrobiology, Seeger and her colleagues described how living cells can be held high above the hot surface of Venus and survive, passing into a state of suspended animation during the most critical periods. At the same time, most of their active existence takes place at an altitude of 48-60 kilometers, where the temperature is quite moderate and is 50-60 ° С: for comparison, below, at the surface, it reaches 460 ° С, deadly for all living things.
In these layers, the Venusian atmosphere is filled with sulfuric acid particles – a product of local volcanic activity – but it also contains some water. In theory, microbes that have found themselves here may well live, relying on a still unknown and exotic form of metabolism. In this case, the main danger for them is falling down into the hotter layers of the atmosphere.
However, with an increase in the mass of droplets, a decrease in height is inevitable, as a result of which microbes can descend to a height of 33-48 kilometers, into deeper layers, where the temperature already reaches 77-187 ° C. Here, the liquid quickly heats up and evaporates, leaving the microbes only one way to survive: to stop metabolism and go to a protected state of suspended animation, as do, for example, many terrestrial bacteria that form spores.
Over time, some of them will be again lifted by updrafts to a more favourable height, will be saturated with water and resume metabolism. Note that the question of how exactly it can be organized remains unanswered: the pH of the local environment is too low for ordinary nucleic acids, proteins, or just sugars to remain stable – with such an amount of acid, they quickly oxidize.
Nevertheless, we know too little about the possibilities and diversity of life. Therefore, the authors of the work hope that future Venusian missions will search for organic matter in the atmosphere of a neighbouring planet. And if they are found, then the question of the existence of life there will be much more serious than it seems now.