Was Kalyke an interloper?

Two competing ideas for how a very red moon ended up in the Carme family.

Published 2026-10-23

Kalyke’s colour raises a question: is it really a piece of the same parent as the other Carme moons?^[4]

The family background

The Carme group is thought to be the fragments of a single body about 46 km across, probably a D-type asteroid from the Hilda family or the Jupiter trojans.^[4]

Idea 1: an outsider

Kalyke’s strong redness matches centaurs or trans-Neptunian objects, suggesting it may be an interloper from the outer Solar System.^[4][1]

Idea 2: the impactor

Kalyke might be a remnant of the object that collided with the Carme parent, rather than a fragment of the parent itself. But it would be unusual for such a remnant to settle into a post-collision orbit so similar to the body it hit.^[4]

Still open

The original observers said more observations were needed to confirm its red colour.^[1]

Numbered citations link to the sources list on the Kalyke overview page.