Scientists believe they have found an explanation for the “unusual radar signals” found in the far reaches of the solar system.
The icy satellites orbiting Jupiter and Saturn have baffled scientists because they are so different from both the rocky worlds and most of the ice on Earth. The distinctly different radar signals have raised questions about their composition.
The objects are also very bright, even in areas where it would be expected to be dark.
“Six different models have been published in an attempt to explain the radar signals from the icy moons orbiting Jupiter and Saturn,” said Jason Hofgartner, co-author of the new study.. “The way these objects scatter radar is fundamentally different from rocky worlds like Mars and Earth, as well as smaller bodies like asteroids and comets.”
Scientists now believe that a specific effect, known as the coherent backscattering resistance effect, or CBOE, likely explains the exceptional radar signals returning from the satellites.
“When you’re facing, the sun is positioned directly behind you on the line between you and an object, and the surface appears much brighter than it would otherwise,” Hofgartner said. It’s known as the opposition effect. In the case of radar, the transmitter replaces the sun and the receiver.
On an icy surface, the effect is more intense. The light is scattered as it bounces off the ice, making it brighter.
“I think that tells us that the surfaces of these objects and their surfaces under many meters are very turbulent,” said Dr. Hofgartner. “They are not very uniform. The landscape is dominated by rock icicles, perhaps looking like a chaotic catastrophe after a landslide. This would explain why light is bouncing around in so many different directions and emitting unusual polarization signals.”
The work is described in the article “Sequence of Icy Satellite Radar Characteristics Requiring the Coherent Backscattering Effect,” published in natural astronomy today.
It is based on research published in the 1990s that suggested CBOE as an explanation for those unusual radar signals. The researchers then suggested that other explanations may be responsible for the strange data.
But the new work builds on the model behind that theory, and the researchers say it is now the only process that would explain all of the different and unexpected properties of satellites.
translation Michelle Padilla
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