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https://www.space.com/astronomy/solar-system/hubble-telescope-watched-jupiters-moon-europa-for-14-years-and-now-scientists-arent-sure-if-its-ejecting-water-after-all
Scientists thought Jupiter's moon Europa was ejecting water. Now they're
not so sure
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By Robert Lea published 4 hours ago
"The evidence for water vapor plumes on Europa isnrCOt as strong as we
first understood it."
(Main) Jupiter's moon Europa and (Inset) Hubble Space Telescope
(Main) Jupiter's moon Europa and (Inset) Hubble Space Telescope (Image
credit: NASA)
Astronomers have studied 14 years of Hubble Space Telescope observations
of Jupiter's icy moon Europa, and now suspect that its infamous water
vapor eruptions may not exist as was previously thought
Europa has long been a hot target for scientists aiming to investigate
the habitability of nearby worlds and the possible existence of life
elsewhere in the solar system. That is because this Jovian moon is
thought to host a global subsurface ocean that possibly harbors some of
the essential elements for life under its thick and icy shell, including complex organic chemicals and water.
The faint and difficult-to-detect plumes were previously thought to
originate from the vast global saltwater ocean lurking beneath the icy
shell of Europa. This material is thought to erupt from cracks in the
icy shell of the moon. Now, previous evidence of the existence of these
plumes has been called into question by the very scientists who
initially proposed them.
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"The evidence for water vapor plumes on Europa isnrCOt as strong as we
first understood it," team member Kurt Retherford of the Southwest
Research Institute (SwRI) said in a statement. Retherford was part of a
team that in 2014 suggested the existence of these European water
plumes, but he and his colleagues now reconsider this conclusion.
Another look at Europa
To reconsider the existence of Europa's water plume eruptions,
Retherford and colleagues looked at 14 years of data regarding Europa collected by Hubble using its HST/STIS instrument (Hubble Space
TelescoperCOs Space Telescope Imaging Spectrograph). In particular, they
honed in on a specific wavelength of ultraviolet light called
Lyman-alpha emissions, which is emitted and scattered by hydrogen atoms.
Retherford and team had been detecting Lyman-alpha emissions from Europa between 2012 and 2014, but this investigation was pushing Hubble to its
very limits.
"One of the difficulties in interpreting the data back then was
determining where to place Europa within its context," Retherford
explained. "The way Hubble works left some uncertainty in terms of
placement relative to the center of the image. If EuroparCOs placement was
off even just by a pixel or two, it could affect how the data gets interpreted.rCY
The existence of water vapor plumes on Jupiter’s moon Europa initially reported based in Hubble observations from 2012 are now in doubt
The existence of water vapor plumes on JupiterrCOs moon Europa initially reported based in Hubble observations from 2012 are now in doubt (Image credit: NASA)
The team feared that the detection of water vapor plumes from Europa may
have been the result of "noise" in their data.
"Our reanalysis took our original 99.9% confidence in the plumesrCO
existence and reduced it to less than 90% confidence," team leader
Lorenz Roth of the KTH Royal Institute of Technology, Sweden, said.
"That's simply not enough evidence to support the certainty of claims we
made at the time."
The team still can't confidently rule out the existence of Europa's
water vapor, especially as similar plumes have been more confidently
detected on Saturn's icy moon of Enceladus, and sulfur dioxide eruptions
have been detected from Europa's fellow Jovian moon of Io, the most
volcanic body in the entire solar system.
The question of the existence of these water plumes and the salty global
ocean of Europa may finally be settled in 2030 when NASA's Europa
Clipper mission arrives in the Jovian system.
The team's research was published on May 5 in the journal Astronomy & Astrophysics.
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