Enceladus, Saturn's potentially habitable moon, experienced a catastrophic collision with a large object in the past that turned its axis of rotation 55 degrees, according to NASA's Jet Propulsion Laboratory.
“The geological activity at the south pole of Enceladus, which we see with the help of Cassini, could not start by itself, as a result of some internal processes in the bowels of the planet. We believe that the "tiger stripes" were originally located closer to the equator, and the catastrophic collision of Enceladus and an asteroid could have spawned them and rotated the moon's axis of rotation, "said Radwan Tajeddine of Cornell University (USA).
In 2005, Cassini discovered jets of water ice and steam particles on Enceladus, which are thrown into space from parallel cracks near the South Pole - the so-called "tiger stripes". This discovery raised the question of the source of this steam and ice.
In March 2015, 10 years after the discovery of tiger stripes and geysers at Enceladus, the Cassini probe showed that there is a global ocean of liquid and hot water in the bowels of this moon of Saturn, detecting sand particles and frozen water droplets ejected from the South Pole Enceladus along with geyser eruptions.
According to Tajeddin, the presence of such structures at the south pole and their absence at the north pole of the planet, covered with a thick crust of ice, made scientists think about how these structures could have arisen, through which heat leaves the interior of Enceladus today, heated by the tidal forces of Saturn.
In an effort to understand how Enceladus began to look as we see it today, scientists analyzed the topography of its surface, trying to find traces of geological processes that could explain the presence of geysers at its south pole.
Scientists were interested in how the height of the terrain differs in different regions of Enceladus, and in which direction the stripes and other structures that have arisen as a result of geological processes on the surface of the moon of Saturn were "turned".
The shape of the planet and how various geological "landmarks" are located on it, as Tadjeddin and his colleagues suggested, were supposed to show whether the stripes arose by themselves, due to the activity of the interior of Enceladus, or whether they were generated by some "external" events - interactions with a giant planet or collisions with asteroids.
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A map of the poles of Enceladus in the past and today / Photo: NASA / JPL-Caltech / Space Science Institute / Cornell University
Analysis of images from "Cassini" led to unexpected results - all the forms of relief that scientists managed to find on the surface of Enceladus did not appear where they should have appeared if the planet had always looked like that. In particular, the "tiger stripes" and three large lowlands on Enceladus were supposed to appear in the equatorial, not in the circumpolar regions.
The calculations of the authors of the article show that such anomalies can be explained by the fact that the axis of rotation of Enceladus in the distant past was rotated by 55 degrees, as a result of a collision with a large asteroid or the debris of Saturn's moon. When this happened, Enceladus became temporarily unstable and its axis of rotation began to "wobble", changing position for quite a long time. These "wobbles" of the axis gave rise to a special pattern on the surface of Enceladus, similar in shape to a stretched S letter.
In addition, this asteroid, according to scientists, "pierced" the ice shell of the planet in the area of the modern South Pole and gave rise to geysers and other traces of internal activity that Cassini could see in the past phases of its work in the orbit of Saturn. This explains the differences in the appearance of the poles and makes scientists wonder if Enceladus was as interesting to us in terms of the origin of life in the past as it is today.