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hubie [soylentnews.org] writes:

The northern plains on Mars has a large, smooth region [wikipedia.org] suggestive of once harboring an ocean, but there are no signs of an ancient shoreline. New research from Rodriguez, et al., published in Nature Science Reports [nature.com], looked at features such as sedimentary deposits, boulder alignments, and backwash channels, and they infer that the region was hit by at least two Tsunamis [eos.org], most likely caused by meteor strikes.

The evidence suggests that two separate tsunamis stormed through the ocean—which encircled the north pole and could have been one third the size of the entire globe—some millions of years apart. The new signs of a Martian ocean sustained for millions of years between meteorite impacts bolster the possibility that the Red Planet offered a tolerable environment for life at the time, the researchers said.

From the open access paper [nature.com] abstract:

It has been proposed that ~3.4 billion years ago an ocean fed by enormous catastrophic floods covered most of the Martian northern lowlands. However, a persistent problem with this hypothesis is the lack of definitive paleoshoreline features. Here, based on geomorphic and thermal image mapping in the circum-Chryse and northwestern Arabia Terra regions of the northern plains, in combination with numerical analyses, we show evidence for two enormous tsunami events possibly triggered by bolide impacts, resulting in craters ~30 km in diameter and occurring perhaps a few million years apart. The tsunamis produced widespread littoral landforms, including run-up water-ice-rich and bouldery lobes, which extended tens to hundreds of kilometers over gently sloping plains and boundary cratered highlands, as well as backwash channels where wave retreat occurred on highland-boundary surfaces. The ice-rich lobes formed in association with the younger tsunami, showing that their emplacement took place following a transition into a colder global climatic regime that occurred after the older tsunami event. We conclude that, on early Mars, tsunamis played a major role in generating and resurfacing coastal terrains.

Original Submission