Jupiter’s moon Europa is one of a handful of worlds in our solar system that could potentially harbor conditions suitable for life. Previous research has shown that beneath its water-ice crust lies a salty ocean of liquid water with a rocky seafloor. However, planetary scientists had not confirmed if that ocean contained the chemicals needed for life, particularly carbon.
Astronomers using data from NASA’s James
Webb Space Telescope have identified carbon dioxide in a specific region on the
icy surface of Europa. Analysis indicates that this carbon likely originated in
the subsurface ocean and was not delivered by meteorites or other external
sources. Moreover, it was deposited on a geologically recent timescale. This
discovery has important implications for the potential habitability of Europa’s
ocean.
This graphic shows a map of Europa’s surface with NIRCam (Near Infrared Camera) on NASA’s James Webb Space Telescope in the first panel and compositional maps derived from Webb’s NIRSpec/IFU (Near Infrared Spectrograph’s Integral Field Unit) data in the following three panels. In the compositional maps, the white pixels correspond to carbon dioxide in the large-scale region of disrupted chaos terrain known as Tara Regio (center and right), with additional concentrations within portions of the chaos region Powys Regio (left). The second and third panels show evidence of crystalline carbon dioxide, while the fourth panel indicates a complexed and amorphous form of carbon dioxide. Credits: Science Credit: Geronimo Villanueva (NASA/GSFC), Samantha Trumbo (Cornell Univ.), NASA, ESA, CSA. Image Processing Credit: Geronimo Villanueva (NASA/GSFC), Alyssa Pagan (STScI)
“On Earth, life likes chemical
diversity – the more diversity, the better. We’re carbon-based life.
Understanding the chemistry of Europa’s ocean will help us determine whether
it’s hostile to life as we know it, or if it might be a good place for life,”
said Geronimo Villanueva of NASA’s Goddard Space Flight Center in Greenbelt,
Maryland, lead author of one of two independent papers describing the findings.
“We now think that we have
observational evidence that the carbon we see on Europa’s surface came from the
ocean. That's not a trivial thing. Carbon is a biologically essential element,”
added Samantha Trumbo of Cornell University in Ithaca, New York, lead author of
the second paper analyzing these data.
NASA plans to launch its Europa Clipper spacecraft, which will perform dozens of
close flybys of Europa to further investigate whether it could have conditions
suitable for life, in October 2024.
A
Surface-Ocean Connection
Webb finds that on Europa’s
surface, carbon dioxide is most abundant in a region called Tara Regio – a
geologically young area of generally resurfaced terrain known as “chaos
terrain.” The surface ice has been disrupted, and there likely has been an exchange
of material between the subsurface ocean and the icy surface.
“Previous observations from the
Hubble Space Telescope show evidence for ocean-derived salt in Tara Regio,”
explained Trumbo. “Now we’re seeing that carbon dioxide is heavily concentrated
there as well. We think this implies that the carbon probably has its ultimate
origin in the internal ocean.”
“Scientists are debating how much
Europa’s ocean connects to its surface. I think that question has been a big
driver of Europa exploration,” said Villanueva. “This suggests that we may be
able to learn some basic things about the ocean’s composition even before we
drill through the ice to get the full picture.”
Both teams identified the carbon
dioxide using data from the integral field unit of Webb’s Near-Infrared Spectrograph (NIRSpec). This instrument mode provides spectra with a
resolution of 200 x 200 miles (320 x 320 kilometers) on the surface of Europa,
which has a diameter of 1,944 miles, allowing astronomers to determine where
specific chemicals are located.
Carbon dioxide isn’t stable on
Europa’s surface. Therefore, the scientists say it’s likely that it was
supplied on a geologically recent timescale – a conclusion bolstered by its
concentration in a region of young terrain.
“These observations only took a few
minutes of the observatory’s time,” said Heidi Hammel of the Association of
Universities for Research in Astronomy, a Webb interdisciplinary scientist
leading Webb’s Cycle 1 Guaranteed Time Observations of the solar system. “Even
with this short period of time, we were able to do really big science. This
work gives a first hint of all the amazing solar system science we’ll be able
to do with Webb.”
NIRCam (the Near Infrared Camera) on NASA’s James Webb Space Telescope captured this picture of the surface of Jupiter’s moon Europa. Webb identified carbon dioxide on the icy surface of Europa that likely originated in the moon’s subsurface ocean. Credits: Science Credit: Geronimo Villanueva (NASA/GSFC), Samantha Trumbo (Cornell Univ.), NASA, ESA, CSA. Image Processing Credit: Geronimo Villanueva (NASA/GSFC), Alyssa Pagan (STScI
Searching for
a Plume
Villanueva’s team also looked for
evidence of a plume of water vapor erupting from Europa’s surface. Researchers
using NASA’s Hubble Space Telescope reported tentative detections of plumes
in 2013, 2016,
and 2017.
However, finding definitive proof has been difficult.
The new Webb data shows no evidence
of plume activity, which allowed Villanueva’s team to set a strict upper limit
on the rate of material potentially being ejected. The team stressed, however,
that their non-detection does not rule out a plume.
“There is always a possibility that
these plumes are variable and that you can only see them at certain times. All
we can say with 100% confidence is that we did not detect a plume at Europa
when we made these observations with Webb,” said Hammel.
These findings may help inform
NASA’s Europa Clipper mission, as well as ESA’s (European Space Agency’s)
upcoming Jupiter Icy Moons Explorer (JUICE).
The two papers will be published in
Science on Sept. 21.
The James Webb Space Telescope is the world's premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.
Source: NASA’s Webb Finds Carbon Source on Surface of Jupiter’s Moon Europa | NASA
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