Jupiter’s moon Europa has an icy crust covering a vast, global ocean. The rocky layer underneath may be hot enough to melt, leading to undersea volcanoes.
New research and computer modeling show that volcanic
activity may have occurred on the seafloor of Jupiter’s moon Europa in the
recent past – and may still be happening. NASA’s upcoming Europa Clipper mission, targeting a 2024 launch, will swoop close to the icy moon
and collect measurements that may shed light on the recent findings.
Scientists have strong evidence that Europa harbors an
enormous ocean between its icy crust and rocky interior. The new work shows how
the moon may have enough internal heat to partially melt this rocky layer, a
process that could feed volcanoes on the ocean floor. The recent 3D modeling of
how this internal heat is produced and transferred is the most detailed and thorough
examination yet of the effect this interior heating has on the moon.
The key to Europa’s rocky mantle being hot enough to
melt lies with the massive gravitational pull Jupiter has on its moons. As
Europa revolves around the gas giant, the icy moon’s interior flexes. The
flexing forces energy into the moon’s interior, which then seeps out as heat
(think of how repeatedly bending a paperclip generates heat). The more the
moon’s interior flexes, the more heat is generated.
The research, published recently in Geophysical Research
Letters, models in detail how Europa’s rocky
part may flex and heat under the pull of Jupiter’s gravity. It shows where heat
dissipates and how it melts that rocky mantle, increasing the likelihood of
volcanoes on the seafloor.
Volcanic activity on Europa has been a topic of
speculation for decades. By comparison, Jupiter’s moon Io is obviously volcanic. Hundreds of volcanoes there erupt lava
fountains and eject volcanic gas and dust up to 250 miles (400 kilometers) high
– activity that is due to the same kind of internal heating caused by Jupiter’s
pull. But Europa is farther away than Io is from its host planet, so scientists
have wondered whether the effect would be similar under the icy surface.
Led by Marie Běhounková of Charles University in the
Czech Republic, the authors further predicted that volcanic activity is most
likely to occur near Europa’s poles – the latitudes where the most heat is
generated. They also looked at how volcanic activity may have evolved over
time. Long-lived energy sources give more opportunity for potential life to
have developed.
Underwater volcanoes, if present, could power
hydrothermal systems like those that fuel life at the bottom of Earth’s oceans.
On Earth, when seawater comes into contact with hot magma, the interaction
results in chemical energy. And it is chemical energy from these hydrothermal
systems, rather than from sunlight, that helps support life deep in our own
oceans. Volcanic activity on Europa’s seafloor would be one way to support a
potential habitable environment in that moon’s ocean.
“Our findings provide additional evidence that
Europa’s subsurface ocean may be an environment suitable for the emergence of
life,” Běhounková said. “Europa is one of the rare planetary bodies that might
have maintained volcanic activity over billions of years, and possibly the only
one beyond Earth that has large water reservoirs and a long-lived source of
energy.”
Direct Observations
NASA scientists will have the opportunity to put the
new predictions to the test when Europa Clipper reaches its target in 2030. The
spacecraft will orbit Jupiter and perform dozens of close flybys of Europa to
map the moon and investigate its composition. Among the science data it
collects, the spacecraft will survey the surface in detail and sample the
moon’s thin atmosphere.
The surface and atmosphere observations will give
scientists a chance to learn more about the moon’s interior ocean if the water
percolates up through the icy crust. Scientists believe the exchange of
material between the ocean and the crust would leave traces of seawater on the
surface. They also believe the exchange may emit gas, and possibly even plumes
of water vapor, with ejected particles that could contain materials coming from
the seafloor.
As Europa Clipper measures the moon’s gravity and
magnetic field, anomalies in those areas, especially toward the poles, could
help confirm the volcanic activity predicted by the new research.
“The prospect for a hot, rocky interior and volcanoes
on Europa’s seafloor increases the chance that Europa’s ocean could be a
habitable environment,” said Europa Clipper Project Scientist Robert Pappalardo
of NASA’s Jet Propulsion Laboratory in Southern California. “We may be able to
test this with Europa Clipper’s planned gravity and compositional measurements,
which is an exciting prospect.”
Image & info via NASA
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