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A long history of water and cratering

Located in the ancient Noachia Terra region within the Margaritifer Sinus quadrangle, the Holden Basin lies adjacent to Holden crater, named after the American astronomer Edward Singleton Holden (1846-1914). Today, the crater and the basin are part of the so-called Uzboi-Ladon-Morava-outflow system, also called ULM system.

Before the impact that created the 140 km in diameter Holden crater, the ULM outflow system was a long series of channels and sinks that emerged from the Argyre basin and traversed northward through Uzboi Vallis into Holden Basin, a large, ancient impact structure. From there it leads through Ladon Valles into Ladon basin, another very large ancient impact basin (see dashed lines in global overview map). It continues through Morava Valles towards the sink of the Margaritifer basin. Even Ares Vallis is believed to have been created by the outflows of the ULM system (see global and overview map images). Taken together, the total area drained may have reached up to 9% of the Martian surface. The impact that created Holden crater most likely happened in the Late Noachian, after the main activity of the ULM. The impact and formation of Holden crater interrupted the ULM outflow system, but Uzboi Vallis to the south breached the up to 900 m high crater walls making Holden the terminal basin for Uzboi and Nigral Valles. Although there is no visible outlet valley at Holden, an area of collapse can be spotted at the eastern side of the crater towards Holden Basin. There is no evidence for significant discharge and through-flowing after the impact, but some minor discharge may have happened along the ULM system after Holden crater was formed. Certainly, the floor of Holden basin was filled with large amounts of ejecta material subsequent to the impact forming Holden crater.