The Curiosity rover's images show a network of irregular hexagons that could have been formed by regular moistening and drying of the ground. It seems that several billion years ago, this area was periodically flooded with water and then dried up, which created optimal conditions for the emergence of life.
Today, there is no doubt that Mars was a fairly wet planet in the distant past. Traces of the effects of water are found everywhere on it, from minerals to the beds of ancient streams. The question remains, however, where and in what form it was present. Did it form long-standing lakes or even oceans, or was it mostly preserved as ice and only occasionally thawed?
New findings from the Curiosity rover have shown that at least some periods of the past on Mars had seasonal cycles, with water flowing in and out. Such variable conditions are considered optimal for the emergence and development of early life.
Curiosity has been operating in Gale Crater since 2012. William Rapin (William Rapin) and his colleagues from the French Institute of Astrophysics and Planetology in Toulouse found that the device took off there very characteristic structures that resemble a network of irregular hexagons in the size of a few centimeters and with cracks up to ten centimeters deep. Such shapes are formed when liquid-saturated soil dries out and often appear on Earth.
The authors showed that this section of the surface was formed about 3.6 billion years ago, during the Hesperian period of Mars' geologic history. Since then, the cracks have eroded a lot, and it is not surprising that until now scientists simply did not notice the hexagonal structures. In addition, they are characterized by their small size.
Such a size suggests that the liquid penetrated into the ground to a not too great depth, no more than a few centimeters. This means that the water most likely covered the surface only temporarily and soon dried up. In addition, the correct angles between the individual hexagons are formed only for several cycles of moistening and drying. Therefore, the scientists concluded that during the Hesperian period in this area there were regular (possibly seasonal) spills of water followed by drying up.
"An environment with cycles of wetting and drying is considered important, and possibly necessary, for pre-biological chemical evolution," the authors of the new paper emphasized.
Indeed, most reactions leading to the formation of complex organic and biological compounds are accompanied by the release or binding of water molecules. The former are much easier to pass in relatively dry conditions, the latter - in wet conditions. In addition, desiccation promotes precipitation and increased concentration of the resulting substances. All this creates the conditions that lead to the emergence of primitive life. However, its traces on Mars have yet to be found.