The news article Impact crater linked to Martian tsunamis describes results of numerical calculations which address the possibility that a giant martian tsunami triggered by an impact has left recognizable features on the martian landscape. The research is published in the Journal of Geophysical Research - Planets, but as of this moment the DOI link there doesn't seem to work. However, it seems to be:
Costard et al. 2017, Modeling tsunami propagation and the emplacement of thumbprint terrain in an early Mars ocean, DOI: 10.1002/2016JE005230,
The identification of lobate debris deposits in Arabia Terra, along the proposed paleoshoreline of a former northern ocean, has renewed questions about the existence and stability of ocean-sized body of water in the early geologic history of Mars. The potential occurrence of impact-generated tsunamis in a northern ocean was investigated by comparing the geomorphologic characteristics of the Martian deposits with the predictions of well-validated terrestrial models (scaled to Mars) of tsunami wave height, propagation direction, runup elevation, and distance for three potential sea levels. Our modeling suggests several potential impact craters ~30–50 km in diameter as the source of the tsunami events. Within the complex topography of flat-floored valleys and plateaus along the dichotomy boundary, the interference of the multiple reflected and refracted waves that are observed in the simulation may explain the origin of the arcuate pattern that characterizes the thumbprint terrain.
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I can not access the article yet, but the BBC interview with Costard leaves me puzzled about the speed of tsunamis:
Two successive waves were formed during the event, says François Costard. "It was a really large-scale, high speed tsunami. At the very beginning, a crater of 70km in diameter was created by the impact. This expelled a huge volume of water, with wave propagation at 60m/second," he explained. (emphasis added)
"The initial wave was about 300m in height. After just a few hours, that tsunami wave reached the palaeo-shoreline located at a few hundred km from the impact crater."
This gigantic wave washed over hills and plateaus and through valleys, leaving behind the lobate flow deposits.
"Finally... due to the Martian ocean filling in that crater, which produced a kind of rebound, there was a second wave propagation," Dr Costard added.
60m/s is 216 km/h, and this is consistent with a few hundred km in a few hours also mentioned.
Question: If I just google the speed of a Tsunami on Earth, I see 800 km/h. The surface gravity on Mars is about 3.71 m/s^2, or about a factor of 2.6 lower than that of Earth. Does this explain the factor of 4 slower speed of the Tsunami wave quantitatively?
below: "The thumbprint terrains probably formed when two sets of tsunami waves interacted." from here.