Volcanic eruptions are common on Earth, but do they occur in other worlds of our solar system? For years, the Earth was the only known world that had active volcanoes on its surface. Although evidence of volcanic activity has been found on the Moon and other rocky planets, scientists have yet to find evidence of active volcanoes. All of that changed during the overflights of Jupiter’s Voyager 1 and Voyager 2 in the late 1970s. When images of Jupiter’s innermost moon, Io, were sent to Earth, scientists found clear evidence of volcanic eruptions on the surface of Io. Io became the first different world on Earth where active volcanoes were observed. In the following decades, scientists began to find active volcanoes in many other worlds.
The Inner Solar System
Venus is covered with volcanic surface features, but no active volcanoes have yet been observed on Venus. NASA
Earth is the only planet in the inner solar system where volcanic eruptions have been observed. However, each of the rocky planets has surfaces that have been shaped by volcanic activity. The surface of Mercury is covered with volcanic formations, suggesting that early in its history, Mercury experienced volcanic eruptions. Today, Mercury’s core has probably solidified, ending any volcanic activity. Venus is a completely different story. The entire surface of Venus is of volcanic origin and data suggest that most of these volcanic features are less than 500 million years old. Venus is believed to be a geologically active world that is still experiencing volcanic eruptions, but scientists have not yet confirmed current volcanic activity. The reason why no volcanic eruptions have been observed on Venus may have to do with the fact that Venus experiences a global volcanism, where the entire surface erupts every few hundred million years. We may have to wait a while before any volcano erupts.
Mars is home to the largest volcanoes in the solar system, but it is not yet known if any of them are active. The core of Mars is believed to have solidified in the last billion years, and as a result, volcanic activity probably ceased. There is evidence of less volcanic activity on the surface in the last hundreds of millions of years, but it is still unknown whether any of Mars’ volcanoes will erupt again.
Volcanic moons
Jupiter’s moon, Io, is the most volcanically active world in the solar system. NASA
One of the most amazing discoveries of our solar system in recent decades has been the discovery of volcanically active moons. As a result, there are more volcanically active moons in the solar system than planets. This is quite interesting, as moons tend to lose their internal heat quite quickly after they form. For a moon to be volcanically active, it must be receiving a continuous supply of energy from an external force. For all the volcanically active moons in our solar system, this energy comes from the friction of the gravitational tide of its host planet. For example, when Io orbits Jupiter, Jupiter’s gravitational attraction stretches and compresses Io, generating friction within its core that moves outward as thermal energy. Interestingly, in relation to its size, Io is the most volcanically active world in the solar system, where there are more than 400 confirmed active volcanoes.
Along with Io, Jupiter is orbited by another volcanically active world called Europe. Like Io, the interior of Europe is heated by the gravitational pull of Jupiter. However, because Europe is made up almost entirely of ice, its volcanoes are not of the type we are familiar with. Europe has what are called cryovolcanoes. Instead of emitting magma, cryovolcanoes in Europe release water and ice. An almost identical situation is developing on Saturn’s moon, Enceladus. Like Europe, Enceladus is composed primarily of ice, and is also home to cryovolcanoes.
Orbiting Neptune is the farthest known world that has active volcanoes. Neptune’s largest moon, Triton, is home to a number of cryovolcanoes. However, unlike the volcanoes of Europe and Enceladus, Triton volcanoes emit mostly liquid nitrogen due to the extremely cold temperatures on their surface. Interestingly, these volcanic eruptions are caused by the fact that Triton orbits Neptune in the wrong way. In other words, the direction of Triton’s orbit is opposite to the rotation of Neptune. This may not seem significant, but it actually means that Triton is doomed. Neptune is slowly stealing Triton’s orbital energy, causing the moon to approach Neptune. This not only makes Triton geologically active, but also causes Triton to be shattered by the gravity of Neptune.
Aidan Remple July 1, 2022 in Science