Five worlds in the solar system have active volcanoes (those that are currently erupting or have erupted in human history): Earth, Jupiter’s moons Io and Europa, Neptune’s moon Triton, and Saturn’s moon Enceladus. But there are several other worlds that show signs of ancient (and not-so-ancient) activity. Let’s explore these explosive places in the solar system.
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Where the lava flows
A volcano is a hole in a planet or moon where hotter material from the interior erupts to the surface or into the air. On Earth, there are hundreds to thousands of active and potentially active volcanoes. On the Big Island of Hawaii is Mauna Loa, the largest active volcano on Earth. It is 5.5 miles (9 km) high, but more than half of it is underwater. Yellowstone National Park in the United States is located in a highly volcanic area. Three eruptions in the distant past created a crater 30-by-45 miles wide (48-by-72 km). Beneath the Pacific Ocean lies the Tamu Massif, a volcano so large that it covers the entire state of New Mexico.
Earth may have many volcanoes, but no place in the solar system is quite like Jupiter’s moon Io. Io is the most volcanic area in the solar system. Every day, hundreds of volcanoes on Io are actively erupting with a shot of lava more than 100 miles above the surface. Io has a lava sea named Loki Patera, which is about a million times larger than typical lava lakes on Earth. And within five months, a mountain the size of Arizona grew over Io. This little moon literally turns inside out.
Cryovolcanoes
There is another cooler type of volcano that spews liquids and ice made of water, methane, ammonia and chlorine instead of lava. Called cryovolcanoes, these eruptions form mountains of ice.
Jupiter’s moon Europa is covered in ice. However, geysers spew material, including water, through fissures in the surface. Scientists believe that the internal heat source causing these eruptions may have melted ice deep within the planet. If true, Europa could hold more water than the entire Earth.
Although Triton, Neptune’s largest moon, is billions of miles from the sun, it has an internal heat source that makes it volcanically active. Volcanoes on Triton spew gases into this otherwise frozen world.
Saturn’s largest moon, Titan, is large enough to hold a thick atmosphere of nitrogen and methane (unfortunately, not much oxygen, so you can’t breathe it). Cryovolcanoes on Titan, Saturn’s largest moon, appear to be spewing gases over the ice surface that add to Titan’s perpetually cloudy climate.
But the undeniably cool cryovolcano champ in the solar system has to be Enceladus, Saturn’s minuscule moon. Enceladus is an icy ball about 313 miles across but it is not a frozen solid. NASA’s Cassini spacecraft has flown by Enceladus several times and observed water geysers erupting from fissures at the moon’s south pole and exploding into space. As the moon orbits Saturn, those icy droplets form a ring around the planet.
Extinct volcanoes
Many worlds in our solar system show signs of ancient volcanoes and lava flows cemented into spectacular rock formations. Sapas Mons, an extinct volcano on Venus, has two peaks. It is 2.5 miles (4 km) high and surrounded by old lava flows and landslides.
The Tharsis region on Mars has 12 large volcanoes. The largest are Olympus Mons, Ascraeus Mons, Pavonis Mons and Arsia Mons. They are up to 100 times larger than any volcanoes on Earth.
Ahuna Mons is a cryovolcano on the dwarf planet Ceres. It grew from eruptions of mud and salty water that froze on the surface. During the New Horizons mission that flew by Pluto in 2015, astronomers saw signs of cryovolcanoes. Ridges and mountains of ice and ammonia are stacked in a typical fashion like icy daggers rising above the flat plain.
Dean Regas is the Astronomer for the Cincinnati Observatory and author of the books 1000 Facts About Space, and How to Teach Grown-Ups About Pluto. For a daily Space Fact, follow him on Instagram:@deanregas.
Tour of the Universe Online Class
What: Astronomer Dean Regas takes you on a virtual tour of everything. Take fast, fun, online classes for all ages and interests, right from your home.
When: Tuesday, April 11, 7 p.m
where: Zoom a webinar.
Tickets: $10/house.
Information: cincinnatiobservatory.org.
First Light Night at the Cincinnati Observatory
What: Celebrate the oldest telescope in the US at 178. Learn about astronomy, tour the buildings and then gaze at the stars in the 178-year-old telescope (weather permitting).
When: Friday, April 14, 8-10 pm
where: Cincinnati Observatory, 3489 Observatory Place.
Tickets: $15/adult, $10/child.
Information: cincinnatiobservatory.org.
