For the first time, astronomers have seen clear evidence of toxic volcanic gas erupting from Io’s volcanoes.
New radio images of Jovian’s moon have finally provided some answers to long-standing questions about the atmosphere.
Io is the most volcanic place in the solar system. More than 400 active volcanoes stain its surface, which is a manifestation of the Moon’s internal stress, as it is gravitationally pulled in different directions not only by Jupiter but also by the other three Galilean moons on the planet.
The thin atmosphere and the surface of Io are dominated by sulfur dioxide – yes, sulfur – distorted from the inside. It emits like gas through volcanic clefts and pastes and settles on the ground at night when it cools, giving the moon a painful yellow and orange hue.
But exactly how much of this gas comes directly from volcanoes, compared to how much comes from frozen surface sulfur dioxide overheated in sunlight? This is difficult to quantify.
“It was not known which process was driving the dynamics in Io̵
“Does volcanic activity or gas sublimate from the icy surface when Io is in sunlight? What we’re showing is that volcanoes actually have a big impact on the atmosphere.”
Finally, researchers have some answers and at the same time have been able to detect jets of volcanic sulfur dioxide on the moon.
Me in infrared light!
taken from the JIRAM instrument aboard the @NASAJuno spacecraft. # Juno #Io #JIRAM # Infrared pic.twitter.com/zO94xqkACI
– Roman Tkachenko (@_RomanTkachenko) April 10, 2018
For a world that is constantly leaking volcanic gas, Io’s atmosphere is surprisingly thin; most of the gas in it leaks through a complex interaction with Jupiter and its magnetic field at a rate of about 1 metric ton per second, contributing to a colossal plasma donut called the Io plasma torus orbiting Jupiter.
The rest of the atmosphere can reveal a lot about the geological processes inside the moon, which in turn can help us understand some of the dynamics of the planets outside our solar system.
If we know exactly the effects of competing gravitational influences on Io and why these influences do not have the same effect on other bodies, we can draw more educated conclusions about how gravitational influences affect exoplanets too far to see well.
So astronomers used the large millimeter / submillimeter massif of the Atacama (ALMA) in Chile to take a closer look at Io below radio wavelengths as it moved in and out of Jupiter’s shadow, the eclipse of Jovian.
The first thing they found was that sulfur dioxide did not stay in Io’s atmosphere. At night the temperature drops below the freezing point of sulfur dioxide.
When this surface reappears in daylight, the frozen sulfur dioxide sublimes back into the atmosphere, filling it in about 10 minutes – much faster than expected.
This strange oddity turned out to be the ideal tool for studying the volcanic atmospheric contribution.
“When Io passes into the shadow of Jupiter and is out of direct sunlight, it is too cold for sulfur dioxide and condenses on the surface of Io,” explained astronomer Lushch-Cook of Columbia University.
“During this time, we can only see sulfur dioxide of volcanic origin. Therefore, we can see exactly how much of the atmosphere is affected by volcanic activity.”
In the ALMA images, the team was able for the first time to clearly identify evidence of sulfur dioxide and sulfur monoxide jets emitted from volcanic sources.
In volcanic areas without sulfur dioxide or monoxide, they saw something else – potassium chloride, another volcanic gas.
This suggests that different volcanoes touch different magma reservoirs instead of sharing them. This suggests some interesting complexity beneath Io’s surface.
From their images, the team was able to calculate the volcanic contribution to Io’s atmosphere. About 30 to 50 percent of sulfur dioxide comes directly from volcanoes.
Obviously, future work will help narrow this down. The team says the next step in their research is to try to measure the temperature of Io’s atmosphere, especially at low altitudes. This will be a little more challenging, but not impossible.
“To measure the temperature of Io’s atmosphere, we need to get a higher resolution in our observations, which requires us to observe the moon for a longer period of time. We can only do this when Io is in sunlight, because it does not spends a lot of time in an eclipse, “de Pater said.
“During such an observation, Io will rotate tens of degrees. We’ll have to implement software that helps us make uncleaned images. We’ve done this before with radio images of Jupiter made with ALMA and a very large array.”
The study is available in two articles, one published in The Planetary Science Journal, and the other in the press with Journal of Planetary Science and uploaded to arXiv.