Fire fountains are a common occurrence in Hawaii. But, there’s evidence these same type of eruptions took place on the Moon. This evidence takes the form of tiny beads of volcanic glass discovered on the lunar surface during the Apollo missions.
Tiny bead of volcanic glass. Credit: Brown University
This week, scientists from Brown University and the Carnegie Institution for Science identified the volatile gas necessary for fire fountain eruptions to take place.
Volatile compounds are a must with fire fountain eruptions. As lava rises towards the surface, these compounds turn into gas. The gas then expands and causes lava to shoot into the air as it reaches the surface – like a fountain.
“The question for many years was what gas produced these sorts of eruptions on the Moon,” said Alberto Saal, associate professor of earth, environmental, and planetary sciences at Brown and one of the authors of the new research. “The gas is gone, so it hasn’t been easy to figure out.”
The first task for researchers was finding a volatile compound. For years, it was believed the Moon didn’t contain any volatiles that could explain fire fountains on the lunar surface. That began to change in 2008 when Saal and his colleagues discovered water in lunar volcanic beads. Additional discoveries soon followed with sulfur, chlorine and fluorine.
But, the compound needed to explain the fire fountains still eluded them.
This week’s research suggests the volatile compound on the moon was large amounts of carbon. The carbon then combined with oxygen to form significant amounts of carbon monoxide. It was this carbon monoxide that is believed to be responsible for the lunar fire fountains that spewed volcanic glass over parts of the moon’s surface.
Let’s look at the science behind the discovery.
Researchers painstakingly studied glass beads brought back to Earth from the Apollo 15 and 17 missions. They soon realized their measurement techniques weren’t good enough to detect the carbon in such a small sample.
Erik Hauri, from Carnegie Institution for Science, developed a new technique to make the detection of carbon possible.
“This breakthrough depended on the ability of Carnegie’s NanoSIMS ion probe to measure incredibly low levels of carbon, on objects that are the diameter of a human hair,” said Hauri. “It is really a remarkable achievement both scientifically and technically.”
With the detection of carbon in hand, the researchers used a model for Earth fire fountains to determine how gases would escape from lunar magma at various depths and pressures. Several parameters needed to be changed to match the conditions on the Moon.
“Most of the carbon would have degassed deep under the surface,” Saal said. “Other volatiles like hydrogen degassed later, when the magma was much closer to the surface and after the lava began breaking up into small globules. That suggests carbon was driving the process in its early stages.”
What does this new research mean?
It gives a potential answer to the longstanding mystery of lunar fire fountains. It also provides evidence that some volatile compounds in the moon’s interior share a common source with those found on Earth.
“The volatile evidence suggests that either some of Earth’s volatiles survived that impact and were included in the accretion of the Moon or that volatiles were delivered to both the Earth and Moon at the same time from a common source — perhaps a bombardment of primitive meteorites,” Saal explains.
Incredible Fire Fountain Eruption from Kilauea Volcano in 1959
Here’s an impressive example of a fire fountain in Hawaii.
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