August of last year was not a good time to hang out on Jupiter’s moon Io, and not just because its atmosphere is inhospitable to human life. NASA reports that the moon suffered a series of three massive volcanic eruptions during a two-week period, leading them to believe such “outbursts” may be more common than previously believed.

Why did they assume that such outbursts weren’t more common? They just weren’t looking often enough:

“We typically expect one huge outburst every one or two years, and they’re usually not this bright,” said Imke de Pater, professor and chair of astronomy at the University of California, Berkeley, and lead author of one of two papers describing the eruptions. “Here we had three extremely bright outbursts, which suggest that if we looked more frequently we might see many more of them on Io.”

Io is the only known place in the solar system (besides Earth) with active volcanoes that spew hot lava above the surface. Because I0 has substantially less gravity than Earth or Jupiter, that lava can travel hundreds of miles into its atmosphere, extending into space.

The eruptions originated from openings that are perhaps less cone-shaped than the volcanoes we know on Earth, instead blasting out of fissures several miles long. The result would have been spectacular “curtains of fire” which, even if eruptions are more common than NASA thought, are still somewhat rare.

“These new events are in a relatively rare class of eruptions on Io because of their size and astonishingly high thermal emission,” said Ashley Davies, a volcanologist with NASA’s Jet Propulsion Laboratory. “The amount of energy being emitted by these eruptions implies lava fountains gushing out of fissures at a very large volume per second, forming lava flows that quickly spread over the surface of Io.”

The first two eruptions were discovered on August 15, 2013, while the third (and brightest) was noted August 29. Eruptions have been documented since 1976, though only 13 large ones were observed between 1976 and 2006. Because Io is believed to be of similar makeup to an infantile Earth or Venus, they aim to study it further to perhaps unlock clues to Earth’s beginnings.

“We are using Io as a volcanic laboratory, where we can look back into the past of the terrestrial planets to get a better understanding of how these large eruptions took place, and how fast and how long they lasted,” Davies said.