Europa’s Nightside Glows within the Darkish

Europa's Nightside Glows in the Dark

In a few years, NASA will send a spaceship to explore Jupiter's icy moon Europa. This orbiter, known as the Europa Clipper mission, will examine the surface more closely to look for plume activity and evidence of biosignatures. Such a find could answer the burning question of whether or not there is life in this moon, which scientists have speculated about since the 1970s.

In anticipation of this mission, the scientists continue to expect what they will find when they get there. For example, scientists at NASA's Jet Propulsion Laboratory recently conducted a study that showed how Europe can glow in the dark. This could be due to the fact that Europe is constantly being hit with high-energy radiation from Jupiter's magnetic field, the investigation of which could tell scientists more about the composition of Europe's ice.

The study, entitled “Laboratory Predictions for Europe's Nocturnal Surface Glow”, was recently published in the journal Nature Astronomy. The study was conducted by Murthy S. Gudipati and Bryana L. Henderson (two researchers from the JPL Science Division) and Fred B. Bateman of the National Institute for Standards and Technology (NIST) in Gaithersburg, Maryland.

Artist concept of a Europe Clipper Mission. Photo credit: NASA / JPL

As they indicated in their study, spectrometer readings have been measured several times in the past by Europe to determine the composition of its ice. These measurements were always obtained by measuring the spectra of the light reflected from the lunar days. However, a spaceship orbiting the moon could collect spectra from the night side and collect spectra directly.

Depending on the presence of various salty compounds, the surface would glow with a combination of unique shimmers. These vary in brightness and color – from light green to light blue or white – depending on the material. As Dr. Gudipati (the study's lead author) stated in a NASA press release that the results he and his colleagues received give a glimpse of what the Europa Clipper might see:

“We were able to predict that this night ice light could provide additional information about the surface composition of Europe. How different this composition is could give us clues as to whether Europe offers viable conditions. "

This is due to the inner ocean of Europe, which sometimes sends material to the surface through renewal events and feathers. In short, by analyzing the surface of Europe, scientists can learn more about what is going on inside. To get a better idea of ​​what direct observations might reveal, the JPL team built the ice chamber for Europe's high energy electron and radiation environment (ICE-HEART) tests.

An artist rendering of Europe and Jupiter based on images sent from a visiting spaceship. Photo credit: NASA / JPL-Caltech

This instrument was brought to NIST's medical industrial radiation facility, where the team conducted experiments to see how organic matter beneath Europe's ice sheet would react to radiation from a high-energy electron beam. As Henderson explained:

“But we never thought that we would see what we ultimately saw. When we tried new ice cream compositions, the glow looked different. And we all just stared at it for a while and then said, “This is new, right? Is this definitely a different glow? "So we set a spectrometer on it and each type of ice had a different spectrum."

Co-author and NIST researcher Fred Bateman was responsible for exposing the ice samples to high-energy electron impacts. What they found (by accident) were variations in the way the ice glowed, which was tied to different compositions. For example, they were surprised to find that sodium chloride brine glowed with a significantly lower intensity than other salts.

This is particularly exciting about the team's research. So it is foreseen how a moon like Europe can shine in the dark. As Gudipati said:

“If Europe weren't under this radiation, it would look like what our moon looks like to us – dark on the dark side. But because it is bombarded by the radiation from Jupiter, it glows in the dark.

"It's not often that you go to a lab and say, 'We may find this when we get there. "Usually it's the other way around. You go there and look for something and try to explain it in the lab. Our prediction, however, comes from a simple observation, and that's what science is about."

Test system for the Europa Clipper. Photo credit: NASA / JPL-Caltech

The Europa Clipper is scheduled to launch in the mid-2020s and reach Jupiter by 2030 or 2031 and create an orbit around the gas giant flyby to fly over another location. This allows the orbiter to collect spectra and other data from almost the entire surface of the moon.

Mission scientists are currently reviewing this study to assess whether a glow can be perceived by the spacecraft's scientific instruments. The results obtained by the Europa Clipper could even be compared with the results of the JPL study in order to identify or limit the salty constituents identified on the surface of Europe.

These and other studies are part of the growing discipline of astrobiology, the interdisciplinary field that deals with life beyond Earth. In addition to capturing composition data and identifying possible biosignatures on Europa, the Europa Clipper could show how other icy moons with inner oceans – like Ganymede, Enceladus, Titan, and many more – might be the best choices for finding extraterrestrial life.

Understanding the habitability of these icy bodies will also help scientists solve the mystery of how life evolved billions of years ago on Earth, not to mention how and where it could exist beyond the solar system.

Further reading: NASA, natural astronomy

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