All in all, Rosaly Lopes, planetary geologist at NASA’s Jet Propulsion Laboratory, has toured 63 active volcanoes and lava lakes — research that helps her better understand such infernos on other planets and moons across the solar system. That dangerous region in Ethiopia, for example, is dotted with yellow and green hot springs that bear striking similarities to Jupiter’s sulfur-studded moon, Io. And Laki, an ancient volcano in Iceland — which last erupted over 200 years ago, spewing a poisonous fog that smothered the globe for nearly a year — looks remarkably similar to a feature on Saturn’s moon Titan.
In 1979, Sicily’s Mount Etna lurched to life, sending a plume of ash and several chunks of molten rock skyrocketing into the air. The outburst was unexpected. And for Rosaly Lopes, continues Shannon Hall in Quanta, a 22-year-old graduate student in planetary science at the time, it was a close call. She and her colleagues had left the summit that morning to work roughly a mile downhill. But others were caught in the terrifying blast, which killed nine people. A man died on his honeymoon. A little boy’s parents were both killed.
“It was a very sobering experience,” Lopes said. But she returned to the summit the next morning, and in the ensuing decades, she has traveled to volcanoes on every single continent. With every trip, she has an evacuation route in mind and knows that if the volcano unexpectedly erupts, she should look skyward to carefully dodge the falling lava bombs. But for many of those volcanoes, lava is not the only danger. She visited a lava lake in Ethiopia a year before several researchers were shot and killed there. She braved the numbing cold of Antarctica to gaze at Mount Erebus, which holds a lava lake that puffs steam and launches lava bombs. And she hoped to visit Nyiragongo, a lava lake in the Congo, earlier this year, but an Ebola outbreak forced her to delay her plans.
Lopes knows these alien features of Jupiter and Saturn’s moons nearly as well as she knows their terrestrial doppelgängers — in part because she discovered most of them. As a planetary geologist at NASA’s Jet Propulsion Laboratory (JPL), she analyzed images from the Galileo mission to Jupiter, identifying 71 active volcanoes on Io — a feat for which she has been recognized with a Guinness World Record. She later found icy volcanoes on Saturn’s moons. And today she focuses her efforts on the tantalizing connection between volcanoes and extraterrestrial life in the outer solar system.
Quanta’s Hall spoke with Lopes about volcanoes across the solar system and the open questions she hopes to soon answer.
Jupiter’s moon Io is the most volcanically active body in the solar system. Left: The dark regions in this image from the Galileo spacecraft show areas of recent volcanic activity. The large dark region toward the center of the image did not exist five months before this picture was taken.
The first mission you worked on at JPL was Galileo. Tell me a little about Jupiter’s moon Io — why is it so exciting?
I was a student when Voyager spotted volcanoes on Io. It was such a sensation because it was beyond what we had seen on Mars, Venus, Mercury and the moon. That this little moon could actually host volcanic activity is pretty phenomenal when you consider that it’s about the size of Earth’s moon. It should have been dead long ago. But it’s not. Instead, Io is a volcanologist’s paradise, with over 150 detected active volcanoes.
But these volcanoes look different that those on Earth. Although Io has mountains, the mountains are not active volcanoes. The volcanoes are calderas on the ground where lava bubbles away. What’s more, when I started working with our highest-resolution data from Galileo, we noticed that several of these calderas showed a pattern with hot edges — a signature of a lava lake. In a lava lake, the crust cools pretty fast, forming this skin of cooler lava on top of the molten lava. That skin then sloshes around and hits the caldera walls where it breaks up and reveals the molten lava underneath. So it’s quite common to actually see hot areas near the margins of the calderas.
But it was a surprising find because lava lakes are very rare on Earth. Although we only have a few, I have now visited nearly all of them, including Mount Erebus in Antarctica.
Photo of Lopes in 2014 above one of the lava lakes at Ambrym, an exceptionally active volcano in the Pacific island nation of Vanuatu.
Have those places helped us understand Io?
Oh yes. We joke that the Danakil Depression — a surreal landscape in Ethiopia that is covered by bright yellow and green hot springs full of sulfur and sulfur dioxide — is like Io on Earth. Not only do the colors resemble Io, but it also has a very active volcano, Erta Ale, with a spectacular lava lake. And that lava lake has helped inform our studies on Io. Like a lot of things, unless you see something up close it can be hard to really understand it. But we saw the lava lake’s hot edges and watched how the crust moved and sunk — all while taking a number of temperature measurements.
Those measurements are key because there is still an open question about the composition of lavas on Io. And while we have no direct measurements on Io, we can use temperature as a proxy because we see on Earth that different lavas melt at different temperatures. Unfortunately, temperatures measured on Io are just on that borderline between basalt — like the lavas you find in Hawaii and elsewhere on Earth — and lavas that are called ultramafic — like the primitive lavas on Earth that erupted mostly billions of years ago.
But if Io’s lavas are truly primitive, then we could study Io in order to better understand what happened on Earth a long time ago. It also makes me wonder if lava lakes were a lot more prevalent in Earth’s past than they are now.
Erta Ale, a volcano in the north of Ethopia, contains a lava lake that has been active for at least five decades.
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