Scientists: Viking-1 might have landed on a field of Martian tsunami debris

The geological history of the Viking-1 Mars landing site

As outlined in their new paper [pdf], a team of scientists now hypothesize that the features that surrounded Viking-1 when it landed on Mars in 1976 were caused by two past Martian tsunamis. Each tsunamis occurred due to an impact in the theorized ocean that is believed to have existed in this part of Mars’ northern lowland plains several billion years ago.

The graphic to the right, figure 8 from the paper, shows the hypothesized sequence of events. From the caption:

(a) Pohl crater forms within a shallow marine environment, (b) triggering tsunami water and debris flow fronts. (c) The wave fronts extensively inundate the highland lowland boundary plains, including a section ~ 900 km southwest of the impact site. (d) The ocean regresses to ~ − 4100 m, accompanied by regional glacier dissection, which erode the rims of Pohl and other craters. (e) The younger tsunami overflows Pohl and parts of the older tsunami. Glaciation continues, and mud volcanoes later source and emerge from the younger tsunami deposit. (f) ~ 3.4 billion years later, the Viking 1 Lander touches down on the edge of the older tsunami deposit.

The overview map below provides the larger context.
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