Mysterious 'Haloes' on Pluto Puzzle Scientists
Strange "haloed" craters can be seen on Pluto in these images of the dwarf planet from NASA's New Horizons spacecraft. Dozens of the strange craters are visible in the black-and-white view (top), while the lower view shows strange methane ice (in purple) around the craters, with water ice (in blue) inside and around them.
Credit: NASA/JHUAPL/SwRI

The discovery of strange halo-like craters on Pluto has raised a new mystery about how the odd scars formed on the icy world.

Pluto's "halo" craters are clearly visible in a new image from NASA's New Horizons spacecraft, which made the first-ever flyby of the dwarf planet in July 2015. In the image, a black-and-white view reveals dozens of ringed craters (NASA describes these formations as "haloed") strewn across the dark landscape of Vega Terra, a region in the far western reaches of the hemisphere photographed by New Horizons during its flyby. The craters have bright walls and rims, making them stand out from their darker surroundings.

While the haloed craters are eye-catching, what has really stumped scientists is what these features are made of. [Pluto Quiz! Are You a Plutophile or Not?]