Instead of hot lava, these cosmic volcanoes spit ice

Ahuna Mons is a big, large volcano Its base is 12 miles across; its summit rises three miles from the surrounding landscape. But that does not mean that he is capable of big eruptions. The last time it exploded, over the past 240 million years, it has not exploded.

Ahuna Mons is what is called a cryovolcano and lies on Ceres, the dwarf planet that is the largest object of the asteroid belt between Mars and Jupiter. Its eruptions have never produced plumes of ash or lava flows, but rather an excretion of ice composed of gases such as ammonia, water and methane. When exposed to the cold expanse of space, the mixture freezes to form a kind of shell, while the interior remains liquid and gas escapes. or flees through the fractures.

Ahuna Mons was first identified in 2015 by NASA's Dawn mission. At the time, it was the only known volcano – glacier or other – on Ceres. In a new document published in Astronomy of natureResearchers say it's not the only one.

A team led by Michael Sori, from the Lunar and Planetary Laboratory at the University of Arizona, studied topographic maps captured by Dawn and found 32 large domes over 6.2 miles in diameter, considered large enough to build up potential volcanoes. Ten of them were excluded from the analysis because impact craters made them difficult to measure reliably. (This is life in an asteroid belt!) The other 22 mounds, however, are likely cryovolcanoes, many of which have long dormant and have somewhat collapsed into the flatter landscape that surrounds them.

The researchers suggest that these volcanoes have been bursting for over a billion years and that some of them may be repeated eruptions. The asymmetry and fractures on Ahuna Mons, for example, are "consistent with multiple episodes, rather than building the entire mountain at one time," says Sori.

On Earth, volcanic activity often generates new land, but not on Ceres. Researchers estimate that ice rashes spewed 100,000 times less volume on Ceres than hotter eruptions on Earth.

Researchers do not know exactly what causes this phenomenon, or whether similar eruptions occur on other asteroids or planetary bodies, such as moons. On Ceres, "we've never seen these eruptions happen in real time," says Sori. "There is no substitute for what happens in real time, but we can speculate intelligently based on our knowledge of regular lava flows." But we are sure they are nothing on Earth .