Researchers examining Jupiter's auroras have found that two of the gas giant's satellites are creating peculiar patterns disturbing the planet's light shows.
Using data gathered by NASA's Juno spacecraft, the researchers have found that one of Jupiter's moons, Io, is leaving behind a luminous trail shaped like a vortex that sometimes split into two on the planet's northern aurora.
Another moon Ganymede has also been seen creating two bright spots, marking the first time scientists have observed double "footprints" created by a moon on its planet's polar lights.
How Auroras Are Made
Polar lights like the aurora borealis in the Earth's north pole and the aurora australis in the south pole are created when charged particles coming from the sun interact with the planet's ionosphere.
Alessandro Mura, study lead author and astrophysicist of Italy's National Institute for Astrophysics, explains that it is similar to a neon lamp. When charged particles called electrons come in contact with gas, the gas lights up.
The same mechanism can be used to explain how auroras appear on other planets. On Jupiter, the polar lights cannot be seen by the naked eye. However, infrared and ultraviolet sensors allow scientists to detect the same effect, which charged particles have on the Jovian atmosphere.
The charged particles coming in contact with Jupiter come from the planet's magnetosphere, a region of space surrounding the planet that contains plasma and magnetic fields.
Io Leaves Behind A Violent Vortex
Astronomers have long known of the strange marks left by Jupiter's moons on its auroras. In fact, the Hubble Space Telescope was able to take images of a bright spot left in the wake of volcanic moon Io as it passes through the plasma in Jupiter's magnetic field. However, the planet's axial tilt has made it difficult for astronomers to take a good look at these spots until now.
With the help of Juno's Jovian Infrared Auroral Mapper, the team of researchers was able to take a closer look at the footprints left behind by Io and Ganymede. Both moons travel treacherously close to Jupiter on their orbits, much closer compared to the moon passing around the Earth.
As they move through Jupiter's magnetosphere, each of the moons generates a wave of charged particles that stream into Jupiter's atmosphere. Io, in particular, creates a whirling vortex-like trail on the northern hemisphere.
The pattern is similar to what is called a Von Karman vortex strait, which appears when a cylinder is placed in a flowing liquid that creates a trail of swirls. Io's trail goes on for 62 miles as the moon passes by.
Two Bright Spots Left By Ganymede
Ganymede also leaves a pair of bright spots separated by at least 62 miles. Mura says they have never seen moons leave behind two spots before.
Ganymede is unique among Jupiter's moons because it is the only satellite with its own magnetic field, meaning, the bright spots may signify the point at which two magnetic fields converge.
"We are seeing the interaction of the magnetosphere of Jupiter inside another magnetosphere," Mura says.
It is unclear what causes the moons to leave a trail. Other moons in the solar system, such as Saturn's Enceladus, have been recording to create the same strange patterns on Saturn's auroras.
Details of the study are published in the journal Science.