BBC-The mountainous ridge that circles the equator on the Saturnian moon Iapetus is both weird and spectacular.
Discovered in 2004, the icy rim is as much as 20km high and runs fully 1,600km from end to end.
No explanation for its existence has yet won total support; it is a puzzle.
Dr Andrew Dombard and colleagues have now made a compelling case for the ridge being the remains of a huge ring of debris that once orbited Iapetus but which eventually fell on to the moon.
“In my opinion, the ridge at Iapetus, which sits right on the equator, is one of the most amazing features that we’ve seen in the Solar System,” the University of Illinois at Chicago (UIC) scientist told BBC News.
“Imagine standing at the base of this ridge. You’d be confronted with a mountain of ice that is taller than the tallest mountain on Earth and nearly as tall as Olympus Mons on Mars, the biggest volcano in the Solar System.
“And it runs ram-rod straight off in either direction. You wouldn’t see it end; you’d just see the ridge disappear over the horizon.”
Dr Dombard has been explaining his team’s thinking here in San Francisco at the American Geophysical Union (AGU) Fall Meeting, the world’s largest annual gathering of Earth and planetary scientists.
The ridge was first identified in images of the 1,400km-wide moon acquired by the Cassini probe in 2004.
Dr Dombard’s group proposes that Iapetus was hit very early in its evolution by another icy body, and that this impact threw an enormous quantity of debris into space.
The researchers argue that this material could then have come together to form a mini-moon or sub-satellite. They liken the situation to the one at dwarf planet Pluto which has a small moon called Charon that was also probably the result of a collision.
Earth’s own Moon was almost certainly made this way, too.