Moons of Haumea

They are thought to be part of its extended collisional family, which formed billions of years ago from icy debris after a large impact disrupted Haumea's ice mantle.

Hiʻiaka, the larger, outermost moon, has large amounts of pure water ice on its surface, which is rare among Kuiper belt objects.

[1] Namaka, about one tenth the mass, has an orbit with surprising dynamics: it is unusually eccentric and appears to be greatly influenced by the larger satellite.

[9] Strong absorption features observed at 1.5, 1.65 and 2 μm in its infrared spectrum are consistent with nearly pure crystalline water ice covering much of its surface.

[10] The sizes of both moons are calculated with the assumption that they have the same infrared albedo as Haumea, which is reasonable as their spectra show them to have the same surface composition.

[4] Because the impact that created the moons of Haumea is thought to have occurred in the early history of the Solar System,[13] over the following billions of years it should have been tidally damped into a more circular orbit.

[15][16] Observation of such transits would have provided precise information on the size and shape of Haumea and its moons,[16] as happened in the late 1980s with Pluto and Charon.

[19] However, in a situation unique among regular satellites, Namaka's orbit was being greatly torqued by Hiʻiaka, which preserved the viewing angle of Namaka–Haumea transits for several more years.