(CNN) -- When the New Horizons mission conducted the closest flyby of Pluto and its moon, Charon, in 2015, images provided a zoomed-in view of their pockmarked surfaces. The scars are ancient impact craters that were created 4 billion years ago.
By studying the craters, astronomers now believe, they have a greater understanding of the mysterious Kuiper Belt objects on the edge of our solar system. A study on their findings was published Thursday in the journal Science.
Kuiper Belt objects are extremely cold remnants from the formation of the solar system that orbit on the edge of it, incredibly far from the sun. These objects are difficult for astronomers to study because they're so faint and far away -- except for larger objects such as Pluto and Charon.
This changed when New Horizons went on to visit Ultima Thule, a Kuiper Belt object 4 billion miles past Pluto, and conduct a flyby of it on January 1.
But now, astronomers may have a new way of studying these objects: by analyzing the craters they left behind on Pluto and Charon.
The craters reveal that small Kuiper Belt objects less than 100 kilometers in size probably created them when they collided with Pluto and Charon. And because of what scientists know about impact crater formation, the fact that no craters were found smaller in 13 kilometers in diameter means there are fewer Kuiper Belt objects smaller than 2 kilometers than astronomers had predicted.
This provides more support for the idea that Kuiper Belt objects are not pieces of space rock formed from collisions but actual intact "leftovers" from when the solar system was forming billions of years ago.
"This surprising lack of small KBOs changes our view of the Kuiper Belt and shows that either its formation or evolution, or both, were somewhat different than those of the asteroid belt between Mars and Jupiter," said Kelsi Singer in a statement, the paper's lead author and a co-investigator of NASA's New Horizons mission. Perhaps the asteroid belt has more small bodies than the Kuiper Belt because its population experiences more collisions that break up larger objects into smaller ones."
Studying Kuiper Belt objects like Ultima Thule is akin to looking at a time capsule of this tumultuous time of formation.
Although there were initially different ideas of what Ultima Thule looks like, for the moment, astronomers are comparing it to a pancake.
The highest-resolution images were released Friday.
The new images revealed that the object features small, dark pits on the surface.
"Whether these features are craters produced by impactors, sublimation pits, collapse pits, or something entirely different, is being debated in our science team," said John Spencer, deputy project scientist from Southwest Research Institute, said in a statement.
Ultima Thule has two sections. The larger lobe is named Ultima, and the smaller is Thule. Ultima looks like a giant pancake, while Thule has been compared to a dented walnut. The object is 20 miles long by 10 miles wide.
"But more importantly, the new images are creating scientific puzzles about how such an object could even be formed," said Alan Stern, mission principal investigator at Southwest Research Institute, in a statement. "We've never seen something like this orbiting the Sun."
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