Jupiter’s moons “hum” — and researchers are trying to figure out why.
New research published Tuesday in
Nature Communications
details the discovery of “whistler” radio waves coming from two of the
moons: Ganymede and Europa. The other two large moons, Io and Callisto,
aren’t subject to this phenomenon.
The finding is interesting because both Europa and Ganymede — the largest moon in the solar system — have subsurface oceans.
“Jupiter’s magnetic field is huge, so it provides us a laboratory test,”
says study lead author Yuri Shprits of GFZ German Research Centre for
Geosciences. “It’s kind of a mini solar system, where you have objects
similar to planets that live in the magnetic field of Jupiter similar to
planets that live in the magnetosphere of the sun.”
In the rest of the solar system, these kinds of whistler waves have
various causes. On Earth, the “hum” of the whistlers — which translate
to sound you can hear when properly processed — are caused by the Van
Allen radiation belts. Earth’s radiation belts accelerate the particles
to high energies, something not seen in the data used in the paper.
Instead, on Jupiter, they’re produced by massive lightning storms.
The astronomers used data from NASA’s now-defunct Galileo space probe,
which explored Jupiter and its moons from 1995 to 2003. That means the
data is old and at times incomplete. It also makes it impossible to
follow up on what’s causing the whistler waves. But the existing data
suggest that both Europa and Ganymede have some kind of magnetic field
coming from within them.
These magnetic fields would vie against the massive magnetic field of
Jupiter, providing an interesting environment far different than the
interactions between Earth and the Sun’s magnetic fields.
The Europa Clipper and Jupiter Icy Moon Explorer missions could provide
more insight. Those will launch next decade, so for now, we’ll need to
be content just knowing that the moons hum — but continue working on the
exact models as to why.
This article originally appeared on Discovermagazine.com.