Craters on Pluto suggest that the Kuiper belt is dominated by large rocks

The photos taken from the dwarf planet and its moon, Charon, by the New Horizons spacecraft change what we know about the mysterious Kuiper belt.

Some antecedents: The Kuiper Belt lies beyond Pluto and is filled with a number of small icy bodies. We do not know much about it, because it is very far away and it is difficult to spot small objects at this distance. However, Pluto has encountered many objects in the Kuiper Belt over the years, creating a representative sample of what really exists.

The news: A study published today in Science estimated the number of objects in the Kuiper belt in different sizes by examining images taken by New Horizons probe during compression by Pluto and Charon in 2015. Images surfaces have shown that rare. While Pluto has changed geologically, Charon has remained relatively stagnant, meaning that craters are unlikely to have been erased. Craters about 13 kilometers long on Charon are made by objects about two kilometers wide, indicating that there are probably not many smaller objects in the Kuiper belt.

What this means: So, why do we care about the size of these icy rocks? The profile of these objects can give clues to the formation of our eight planets. On the one hand, it shows that the formation of the Kuiper belt was different from that of the asteroid belt between Mars and Jupiter, says lead author Kelsi Singer. "Maybe the asteroid belt has more small bodies than the Kuiper belt because its population is undergoing more collisions that break down larger objects into smaller objects," she says.

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