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By Devin Coldewey

The New Horizons probe may be sending back its best pictures of Pluto, but that doesn't mean the dwarf planet's mysteries are any less mysterious. If anything, the improved level of detail is only adding to scientists' perplexity.

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In the latest shot downloaded from the craft, taken on July 14 but only just recently received, a section of the broad, heart-shaped region informally known as Tombaugh Regio is revealed to be covered in small indentations, each hundreds of yards across and 10 or more yards deep.

The region of Pluto's Tombaugh Regio shown in the close-up photo.
The region of Pluto's Tombaugh Regio shown in the close-up photo.NASA/JHUAPL/SwRI

These pits are too numerous and too well aligned with each other to be impact craters — instead, scientists think they may have been formed from ice fracturing and evaporating relatively recently. The patterns and varying depths of these pits may provide clues as to how the surface has changed in recent years and at what rate.

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Other high-resolution images are coming down from New Horizons as well, including a long strip of the planet released Thursday in color. More may be expected as soon as NASA and its partners have a chance to process and present them.