Across the outer reaches of the solar system, a small frozen moon has been quietly holding the memory of its own violent youth. UCLA researchers have used computer modeling to confirm that Charon, Pluto's outsized companion, once rotated more than ten times faster than it does today — and that the slowing of that ancient spin sculpted the fractured mountains and plains still visible on its surface. The work, published in Nature Communications, transforms a geological puzzle observed by New Horizons in 2015 into a legible story of planetary formation, and offers a key for reading the histories