Our solar system is home to a number of strange, intriguing moons. Perhaps one of the most intriguing moons in the Solar System is Saturn’s moon, Enceladus. Enceladus was discovered by astronomer William Herschel in 1789 and named Enceladus by his son. Although its existence has been known for more than two centuries, everything about Enceladus was a mystery until the Voyager flyby in the early 1980s. What the astronomers found was a world unlike anything they had ever seen. The surface of Enceladus was covered in ice. In fact, Enceladus is the most reflective world in the Solar System. Because Enceladus reflects most of the sunlight that hits it, its surface temperature is extremely cold, averaging minus 324 degrees Fahrenheit (minus 198 degrees Celsius). Enceladus is the sixth largest moon in the Solar System with a diameter of 310 miles (500 kilometers). Enceladus orbits Saturn at an average distance of 148,000 miles (238,000 kilometers) and completes one orbit every 33 hours.
Active Moon
An image of Enceladus taken by the Cassini spacecraft. NASA
Despite the success of the Voyager missions, much is still unknown about Enceladus. Therefore, NASA planned the Cassini mission. Cassini will orbit Saturn for more than a decade, taking some of the most stunning images of the ringed planet and its moons. Enceladus was one of Cassini’s most frequently visited worlds. Cassini revealed a world stranger than science fiction. Enceladus’ south pole turned out to be its most interesting feature, and so it was observed by Cassini many times. Enceladus’ south pole appears to be ejecting some material into space. Closer observations revealed that Enceladus is actually releasing vast amounts of water vapor into space. This water was spewed from giant geysers located around the South Pole of Enceladus. The region is named the Tiger Stripes after the large stripes running through the South Pole. Geysers are usually indicators that a world is volcanically active, suggesting that Enceladus’ interior is very hot. This came as a surprise, as small worlds like Enceladus tend to release their heat into space quite quickly. This is why most moons, like ours, are covered in craters and lack evidence of recent activity. That such a small world is so active suggests that Enceladus is supplied with large amounts of energy. Since the sun was too far away to provide enough heat, astronomers looked to Saturn. As Enceladus orbits Saturn, the gas giant’s gravity pulls the tiny moon. This gradually bends Enceladus, stretching the moon when it is far away and compressing it when it is close. This bending creates friction in Enceladus’ core, which melts underground rocks and releases heat. This heat melts underground ice to form a subterranean ocean that can be ten times deeper than Earth’s deepest ocean. The warm subsurface ocean partially melted the surface ice, creating the large cracks and fissures we can see today. As the heat rises to the surface, it also causes large amounts of water to erupt through the ice in the form of geysers. Some of this water vapor flows back and becomes a coating of fresh snow on Enceladus. The rest of the material flows out into space and becomes part of Saturn’s E-ring.
Habitability of Enceladus
Cassini took this image of geysers erupting on Enceladus. NASA
The presence of liquid water on Enceladus makes it a potentially habitable world. In addition to liquid water, the Cassini spacecraft also found organic matter in its geysers, and the geysers themselves suggest that the Moon contains enough energy to support the formation of life. Cassini was able to determine Enceladus’ chemistry by flying past its geysers, sampling the water vapor and determining its composition. Unfortunately, Cassini was not equipped with the technology needed to detect living organisms. If life exists on Enceladus, it’s possible that some organisms ended up ejected into space by geysers. A future mission to Enceladus could fly through the geysers and look for evidence of microscopic organisms.
Aidan Remple July 1, 2022 in Science
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