Saturn’s moon Enceladus is one of these worlds that do not act their (assumed) age.
New Scientist explains:
“Enceladus’ south pole is wounded, bleeding heat and water. Its injury may have come from a huge rock smashing into this frigid moon of Saturn less than 100 million years ago, leaving the area riddled with leaky cracks.”
“The region near Enceladus’ south pole marks one of the solar system’s most intriguing mysteries. It spews plumes of liquid from an interior ocean, plus an enormous amount of heat. The south pole’s heat emission is about 10 gigawatts higher than expected – equivalent to the power of 4000 wind turbines running at full capacity. The rest of the moon, though, is cold and relatively homogeneous.”