Astronomers at the University of California, Los Angeles, utilizing NASA’s Goldstone Solar System Radar and NSF’s Green Bank Telescope, have discovered that the icy surface of Jupiter’s moon Europa scatters radio energy in a remarkably strong and intricate manner, unlike any rocky planet observed to date.
Artist’s impression illustrating radar waves from NASA’s Goldstone Solar System Radar reaching Europa, penetrating its icy surface, and being collected by the NSF’s Green Bank Telescope on Earth. Image credit: NSF/AUI/NSF’s NRAO/P.Vosteen.
Jupiter’s Galilean moons—Europa, Ganymede, and Callisto—are of significant scientific interest due to their icy surfaces and the likelihood of subsurface oceans.
However, radar measurements of ice satellites have not been made since 1987 to 1991.
Radar observations are a powerful tool, as radio waves can penetrate pure ice to considerable depths, unveiling critical insights into the subsurface properties of these celestial bodies and their evolution.
“Radio waves penetrate the ice, providing vital information about its internal structure and purity, allowing radar to investigate deeper than what is visible on the surface,” said Tung-Hui (Tina) Shi, a graduate student at UCLA.
To bridge a longstanding research gap in radar studies, Xie and Professor Jean-Luc Margot conducted observations of Europa from 2011 to 2024 using both the Goldstone Solar System Radar and the Green Bank Telescope.
These groundbreaking observations revealed that Europa’s radar albedo (a measure of its brightness in radar terms) is significantly higher than that of typical planetary bodies and asteroids.
The returning radar signal exhibits the same circular polarization as the transmitted beam, indicating multiple scattering events within clean, porous ice.
These findings lend support to the coherent backscattering opposition effect, which intensifies radio wave echoes as they bounce around within the ice before returning to the telescope.
In a bistatic configuration, where the Goldstone radar transmits and both Goldstone and Green Bank telescopes receive, the researchers were able to investigate how the coherent backscatter effect changes with varying angles between the transmitter, moon, and receiver.
Notably, they discovered that Europa’s radar brightness remained nearly constant as the angle increased, suggesting that the vibrant backscatter “peak” extends beyond the sampled angle range, revealing a limit to how deep radio waves can diffuse before being absorbed.
This depth constraint enhances our understanding of Europa’s ice transparency, aiding scientists in interpreting future ice-penetrating radar data from spacecraft designed to explore the moon in greater detail.
“Future planetary science missions, such as NASA’s Europa Clipper, stand to gain immensely from this radar research,” said Dr. Will Armentrout, a research scientist at the NSF National Radio Astronomy Observatory supporting the radar initiative.
“As the radar technology at the Green Bank Telescope advances, we eagerly anticipate providing even greater radar capabilities to the scientific community.”
For further details, authors present their findings in the result at the 248th American Astronomical Society (AAS) General Meeting in Pasadena, California.
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Xie Tunhui and Jean-Luc Margot. 2026. European radar observations from 2011 to 2024: new insights into radar scattering characteristics. AAS248 Abstract #481
Source: www.sci.news
