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By Devin Coldewey

Images taken by the New Horizons probe during its flyby of Pluto show two of the dwarf planet's moons in far greater detail than ever before. Once mere specks of light to telescopes and more recently a handful of gray pixels, Nix and Hydra have now been imaged with enough definition that shapes and surface features can be discerned.

Related: New Horizons' Latest: Fly Over Pluto's Ice Mountains and Alien Plains

Hydra, Pluto's most distant moon, has a highly irregular shape, and is about 25 miles (40 km) wide and 34 miles (55 km) long. What seem to be craters mark its surface, unlike the largest moon, Charon, and Pluto itself, both of which show evidence of "young," constantly shifting surfaces.

The largely monochromatic Hydra stands in contrast with Nix, the third-closest moon, which has a patch of reddish-brown color on its side. Speculation will have to wait until more more data is downloaded, but team members are excited. "This observation is so tantalizing, I’m finding it hard to be patient for more Nix data to be downlinked," said Carly Howett, mission scientist at Southwest Research Institute in Boulder, in a NASA news release.

Related: Will Pluto Join the Water Worlds? New Horizons' Views Spark Speculation

Though New Horizons has long since sped off toward the more distant regions of the Kuiper Belt, it is still sending back pictures and data collected in a rush during its approach and flyby of Pluto and its moons. There's enough data to keep NASA and its partners busy for months — probably years.