During its journey around Saturn, the Cassini spacecraft captured images of Hyperion – a small moon among the many satellites of Saturn.
This moon is known to scientists thanks to images taken by the Voyager spacecraft over 20 years ago.
However, these earlier images were not sufficiently clear, as Voyager did not approach it closely enough at the time.
The new images taken by Cassini from a distance of 500 km allow astronomers to clearly see the shape and rugged surface of the moon.
Hyperion is considered the most asymmetrical celestial body in the solar system. This “potato-shaped” moon measures about 360 km in length and approximately 225 km in width. Its surface is covered by a network of volcanoes and cliffs that rise up to 10 km high.
Interestingly, as a “dark” moon compared to the other satellites orbiting Saturn, Hyperion reflects only about 30% of the sunlight that hits its surface.
Another distinctive feature is its erratic movement, which does not follow a stable orbit like other moons. It moves chaotically in a difficult-to-predict trajectory due to the combined gravitational forces from Saturn and its largest moon, Titan.
This unusual shape allows it to rotate in two orientations, similar to an unbalanced top. As a result, the cycle of day and night on Hyperion occurs irregularly compared to other celestial bodies.
To date, astronomers have yet to understand the reasons behind Hyperion’s irregular, bumpy shape, while most asteroids and moons of similar size are spherical.
One hypothesis suggests that Hyperion is simply a remnant of a larger moon that fragmented after colliding with meteoroids. However, the answer will depend on further discoveries by Cassini in the coming time.
During its flyby of Hyperion, Cassini’s sensor radars also measured slight changes in the spacecraft’s velocity. This data will help scientists calculate the gravitational forces acting on the spacecraft, which in turn will allow them to determine the mass of this moon.
Astronomers will continue to study and identify the chemical composition of Hyperion in the near future.
