Scientists believe they have an explanation for “anomalous radar signals” seen in the far reaches of the solar system.
The icy moons orbiting Jupiter and Saturn have puzzled scientists because they are rocky worlds and different from most of the ice on Earth. The distinctly different radar signals raised questions about their composition.
Objects are very bright even in areas that are expected to be dark.
“Six different models have been published in an attempt to explain the radar signals of the icy moons orbiting Jupiter and Saturn,” said Jason Hofgardner, co-author of the new study.. “The way these objects scatter radar is completely different from rocky worlds like Mars and Earth, and smaller bodies like asteroids and comets.”
Scientists now believe that a specific effect known as the anti-coherent backscatter effect, or CBOE, explains the unusual radar signals returned from satellites.
“When you’re at opposition, 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,” Hofgardner said. “This is called the opposition effect. In the case of radar, a transmitter replaces the sun and a receiver replaces the eyes.
On an icy surface, the effect is even more extreme. As the light bounces off the ice it scatters, making it even brighter.
“I think the surfaces of these objects and their surfaces several meters below are very disturbed,” Dr. Hofgardner said. “They are not very uniform. Icy rocks dominate the landscape, perhaps looking like a chaotic disaster after a landslide. This explains why light bounces in many directions and produces unusual polarization signals.”
This work is described in an article, ‘Continuity of an ice-satellite radar-characteristics that requires coherent backscatter effect. Natural Astronomy Today.
It suggested CBOE as an explanation for those unusual radar signals based on research published in the 1990s. The researchers suggested that other explanations could account for the strange data.
But new work builds on the model behind that theory, and researchers say it’s the only process that explains the various and unexpected properties of satellites.
Translation Michael Padilla