Just-released images from NASA’s New Horizons spacecraft, which is approaching Pluto, show the two hemispheres of the planet along with its moon, Charon. The right image shows the ring of spots that have mystified scientists.
NASA
July 2, 2015 3:31 PM EDT

Newly released images from NASA’s New Horizons spacecraft show an unusual streak of spots on the dwarf planet Pluto.

Scientists aren’t quite sure what to make of the spots, particularly because they are perfectly spaced apart along the equator and seem nearly identical in width.

“It’s a real puzzle—we don’t know what the spots are, and we can’t wait to find out,” said Alan Stern, of the Southwest Research Institute in Boulder, Colo.

To get the images, scientists merged black-and-white pictures of Pluto and Charon, its largest moon, from the spacecraft’s Long-Range Reconnaissance Imager with color data. The resulting image shows Pluto and Charon in true color.

The spots aren’t the only mystery, however.

“Also puzzling is the longstanding and dramatic difference in the colors and appearance of Pluto compared to its darker and grayer moon Charon,” Stern said.

Scientists are hoping that these questions might be answered as New Horizons approaches Pluto.

Write to Tanya Basu at tanya.basu@time.com.

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