Volcanic eruptions are a common occurrence on Earth, but do they occur on other worlds in our solar system? For years, Earth was the only known world to have 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. That all changed during the Voyager 1 and Voyager 2 flybys of Jupiter in the late 1970s. When images of Jupiter’s innermost moon, Io, were sent back to Earth, scientists found clear evidence of volcanic eruptions on Io’s surface. Io became the first world other than Earth where active volcanoes were observed. In the following decades, scientists began to discover active volcanoes on many other worlds.
The inner solar system
Venus is covered with volcanic surfaces, but active volcanoes have not 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. Mercury’s surface is covered in volcanic formations, suggesting that Mercury experienced volcanic eruptions early in its history. 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 indicate that most of these volcanic features are less than 500 million years old. Venus is believed to be a geologically active world that still experiences volcanic eruptions, but scientists have yet to confirm current volcanic activity. The reason no volcanic eruptions have been observed on Venus may be related to the fact that Venus experiences global volcanism, where the entire surface erupts every few hundred million years. We may just have to wait a while before volcanoes erupt.
Mars is home to the largest volcanoes in the Solar System, but it remains unknown if any of them are active. The core of Mars is thought to have hardened over the last billion years and volcanic activity probably stopped as a result. There is evidence of minor volcanic activity on the surface over the past several hundred million years, but it remains unknown whether any of Mars’ volcanoes will ever erupt again.
Volcanic moons
Jupiter’s moon, Io, is the most volcanically active world in the Solar System. NASA
One of the most stunning discoveries of our solar system in the past few decades has been the discovery of volcanically active moons. As it turns out, there are more volcanically active moons than planets in the Solar System. This is quite interesting as moons tend to lose their internal heat quite quickly after their formation. For a moon to be volcanically active, it must be continuously fed by an external force. For all volcanically active moons in our solar system, this energy comes from the gravitational tidal friction of their host planet. For example, as Io orbits Jupiter, Jupiter’s gravitational pull simultaneously stretches and compresses Io, generating friction in its core that moves outward as heat energy. Interestingly, for its size, Io is the most volcanically active world in the Solar System, home to over 400 confirmed active volcanoes.
Along with Io, Jupiter is orbited by another volcanically active world called Europa. Like Io, Europa’s interior is heated by Jupiter’s gravitational pull. However, because Europa is composed almost entirely of ice, its volcanoes are not of the type we know. There are so-called cryovolcanoes in Europe. Instead of spewing magma, Europa’s cryovolcanoes release water and ice. An almost identical situation is developing on Saturn’s moon Enceladus. Like Europa, Enceladus is composed mostly of ice and is also home to cryovolcanoes.
Neptune’s orbit is the most distant world known to have active volcanoes. Neptune’s largest moon, Triton, is home to a number of cryovolcanoes. However, unlike the volcanoes of Europa and Enceladus, Triton’s volcanoes emit mostly liquid nitrogen due to the extremely low temperatures on its surface. Interestingly, these volcanic eruptions are caused by the fact that Triton orbits Neptune in the wrong direction. In other words, the direction of Triton’s orbit is opposite to Neptune’s rotation. This may not seem significant, but it actually means that Triton is doomed. Neptune slowly steals Triton’s orbital energy, causing the moon to approach Neptune. This not only causes Triton to be geologically active, but also moons that Triton will eventually be torn apart by Neptune’s gravity.
Aidan Remple July 1, 2022 in Science
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