Universe Today
Jupiter's moon
Europa
continues to fascinate and amaze! In 1979, the
Voyager missions
provided the first indications that an interior ocean might exist beneath it's icy surface. Between 1995 and 2003, the
Galileo spaceprobe
provided the most detailed information to date on Jupiter's moons to date. This information bolstered theories about how life could exist in a warm water ocean located at the core-mantle boundary.
Even though the
Galileo
mission ended when the probe crashed into Jupiter's atmosphere, the spaceprobe is still providing vital information on Europa. After
analyzing old data
from the mission, NASA scientists have found independent evidence that Europa's interior ocean is venting plumes of water vapor from its surface. This is good news for future mission to Europa, which will attempt to search these plumes for signs of life.
The study which describes their findings, titled "
Evidence of a plume on Europa from Galileo magnetic and plasma wave signatures
", recently appeared in the journal
Nature Astronomy.
The study was led by Xianzhe Jia, a space physicist from the Department of Climate and Space Sciences and Engineering at the University of Michigan, and included members from UCLA and the University of Iowa.
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Artist's concept of the Galileo space probe passing through the Jupiter system. Credit: NASA
[/caption]
The data was collected in 1997 by
Galileo
during a flyby of Europa that brought it to within 200 km (124 mi) of the moon's surface. At the time, its
Magnetometer (MAG)
sensor detected a brief, localized bend in Jupiter's magnetic field, which remained unexplained until now. After running the data through new and advanced computer models, the team was able to create a simulation that showed that this was caused by interaction between the magnetic field and one of the Europa's plumes.
This analysis confirmed ultraviolet observations made by NASA's
Hubble Space Telescope
in 2012, which suggested the presence of water plumes on the moon's surface. However, this new analysis used data collected much closer to the source, which indicated how Europa's plumes interact with the ambient flow of plasma contained within Jupiter's powerful magnetic field.
In addition to being the lead author on this study, Jia is also the co-investigator for two
instruments
that will travel aboard the
mission - which may launch as soon as 2022 to explore the moon's potential habitability. Jia's and his colleagues were inspired to reexamine data from the
Galileo
mission thanks to Melissa McGrath, a member of the
SETI Institute
and also a member of the
Europa Clipper
science team.
During a presentation to her fellow team scientists, McGrath highlighted other Hubble observations of Europa. As Jiang explained in a recent NASA
press release
:
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Artist's impression of a water vapor plume on Europa. Credit: NASA/ESA/K. Retherford/SWRI
[/caption]
When they first examined the information 21 years ago, the high-resolution data obtained by the MAG instrument showed something strange. But it was thanks to the lessons provided by the
Cassini mission
, which explored the plumes on Saturn's moon
Enceladus
, that the team knew what to look for. This included material from the plumes which became ionized by the gas giant's magnetosphere, leaving a characteristic blip in the magnetic field.
After reexamining the data, they found that the same characteristic bend (localized and brief) in the magnetic field was present around Europa. Jia's team also consulted data from
Galileo's
Plasma Wave Spectrometer
(PWS) instrument to measure plasma waves caused by charged particles in gases around Europa's atmosphere, which also appeared to back the theory of a plume.
This magnetometry data and plasma wave signatures were then layered into new 3D modeling developed by the team at the University of Michigan (which simulated the interactions of plasma with Solar system bodies). Last, they added the data obtained from
Hubble
in 2012 that suggested the dimensions of the potential plumes. The end result was a simulated plume that matched the magnetic field and plasma signatures they saw in the
Galileo
data.
As Robert Pappalardo, a Europa Clipper project scientist at NASA's Jet Propulsion Laboratory (JPL),
indicated
:
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Artist's concept of a Europa Clipper mission, which will study Europa in 2022-2025 to search for signs of life. Credit: NASA/JPL
[/caption]
The findings are certainly good news for the
Europa Clipper
mission, which is expected to make the journey to Jupiter between 2022 and 2025. When this probe arrives in the Jovian system, it will establish an orbit around Jupiter and conduct rapid, low-altitude flybys of Europa. Assuming that plume activity does take place on the surface of the moon, the
Europa Clipper
will sample the frozen liquid and dust particles for signs of life.
"If plumes exist, and we can directly sample what's coming from the interior of Europa, then we can more easily get at whether Europa has the ingredients for life,"
Pappalardo said
. "That's what the mission is after. That's the big picture."
At present, the mission team is busy looking at potential orbital paths for the
Europa Clipper
mission. With this new research in hand, the team will choose a path that will take the spaceprobe above the plume locations so that it is in an ideal position to search them for signs of life. If all goes as planned, the
Europa Clipper
could be the first of several probes that finally proves that there is life beyond Earth.
And be sure to check out this video of the
Europa Clipper
mission, courtesy of NASA:
Further Reading: NASA
,
Nature
