The images have a resolution of about 33 meters, or 110 feet, per pixel. However, because of the rolling of the spacecraft needed to make proper use of the spacecraft’s lower resolution panoramic camera, in addition to the long exposures required by the dim light that far from sun, the images were blurred.

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“It’s a subtle improvement” over earlier images taken at about one-fourth the resolution , said John R. Spencer, one of the deputy project scientists. “It’s grainier because of underexposure.”

Still, even the subtle improvements will give better understanding of the pits and bright patterns on Ultima Thule’s surface. A clearer look at the rims of the pits might help tell whether they are small impact craters or they formed from erosion, for example. Counting craters could reveal the rate of collisions in this distant part of the solar system, while erosion would hold clues to what Ultima Thule is made of.

“We can see much smaller features,” Dr. Stern said. “That brings out much more detail.”