Onderzoekers kraken de code van radarsignaturen van de manen van Jupiter en Saturnus

IJzige satellieten in een baan om Jupiter en Saturnus

Een studie geschreven door Southwest Research Institute Senior Research Scientist Dr. Jason Hofgartner legt de ongebruikelijke radarkenmerken uit van ijzige manen die in een baan rond Jupiter en Saturnus draaien. Hun radarhandtekeningen, die aanzienlijk verschillen van die van rotsachtige werelden en het meeste ijs op aarde, zijn al lang een lastige vraag voor de wetenschappelijke gemeenschap. Krediet: NASA/JPL-Caltech/SwRI

Wetenschappers onthullen oplossingen voor raadselachtige radarkenmerken van de manen van Jupiter en Saturnus

Een gezamenlijk onderzoek onder leiding van Dr. Jason Hofgartner, Senior Research Scientist bij Southwest Research Institute, werpt licht op de raadselachtige radarsignaturen van bevroren satellieten in een baan om de aarde[{” attribute=””>Jupiter and “Six different models have been published in an attempt to explain the radar signatures of the icy moons that orbit Jupiter and Saturn,” said Hofgartner, first author of the study, which was published in Nature Astronomy. “The way these objects scatter radar is drastically different than that of the rocky worlds, such as

The objects are also extremely bright, even in areas where they should be darker.

“When we look up at Earth’s moon it looks like a circular disk, even though we know it’s a sphere. Planets and other moons similarly look like disks through telescopes,” Hofgartner said. “While making radar observations, the center of the disk is very bright and the edges much darker. The change from center to edge is very different for these icy satellites than for rocky worlds.”

In collaboration with Dr. Kevin Hand of

“When you’re at opposition, the Sun is positioned directly behind you on the line between you and an object, the surface appears much brighter than it would otherwise,” Hofgartner said. “This is known as the opposition effect. In the case of radar, a transmitter stands in for the Sun and a receiver for your eyes.”

An icy surface, Hofgartner explained, has an even stronger opposition effect than normal. For every scattering path of light bouncing through the ice, at opposition there is a path in the exact opposite direction. Because the two paths have precisely the same length, they combine coherently, resulting in further brightening.

In the 1990s, studies were published stating that the CBOE was one explanation for the anomalous radar signatures of icy satellites, but other explanations could explain the data equally well. Hofgartner and Hand improved the polarization description of the CBOE model and also showed that their modified CBOE model is the only published model that can explain all of the icy satellite radar properties.

“I think that tells us that the surfaces of these objects and their subsurfaces down to many meters are very tortured,” Hofgartner said. “They’re not very uniform. Icy rocks dominate the landscape, perhaps looking somewhat like the chaotic mess after a landslide. That would explain why the light is bouncing in so many different directions, giving us these unusual polarization signatures.”

The radar observations Hofgartner and Hand used were from the Arecibo Observatory, which was one of only two telescopes making radar observations of icy satellites until it was severely damaged by the collapse of its support structure, antenna, and dome assembly and subsequently decommissioned. The researchers hope to make follow-up observations when possible and plan to study additional archival data that may shed even more light on icy satellites and the CBOE, as well as radar studies of ice at the poles of Mercury, the Moon, and Mars.

Reference: “A continuum of icy satellites’ radar properties explained by the coherent backscatter effect” by Jason D. Hofgartner and Kevin P. Hand, 23 March 2023, Nature Astronomy.
DOI: 10.1038/s41550-023-01920-2

Leave a Reply

Your email address will not be published. Required fields are marked *