The Properties and Origin of Kuiper Belt Object Arrokoth's Large Mounds

We report on a study of the large mounds that dominate the appearance of New Horizons flyby target Kuiper Belt Object (KBO) (486958) Arrokoth's larger lobe, named Wenu. We also find evidence of several crypto-mounds on KBO Arrokoth's smaller lobe, Weeyo, whose present appearance has been affected by for formation of its largest crater, called Sky. We compare the geological context of Wenu's mounds, and measure and intercompare their shapes, sizes/orientations, reflectance, and colors. We find that the mounds are broadly self-similar in many respects, and interpret them as the original building blocks of Arrokoth. Determining whether a characteristic planetesimal building-block size can emerge from Streaming Instability (SI) simulations requires both new simulations at greater resolution than previously undertaken, and a thorough exploration of formation parameter space; regarding that much needed work, we present some promising early modeling results.