Massive meteorite impacts triggered two mega-tsunamis in the early Martian ocean 3.4 billion years ago, according to scientists writing in the journal Scientific Reports, and these enormous waves forever scarred the Martian landscape.
The young Mars would have had enough water to cover its entire surface in a liquid layer about 140 m deep, but it is more likely that the liquid would have pooled to form an ocean occupying almost half of Mars’s northern hemisphere, and in some regions reaching depths greater than 1.6 km. Image credit: M. Kornmesser / ESO / N. Risinger, skysurvey.org.
“About 3.4 billion years ago, a big meteorite impact triggered the first tsunami wave,” said co-author Dr. Alberto Fairén from Cornell University, Ithaca.
“This wave was composed of liquid water. It formed widespread backwash channels to carry the water back to the ocean.”
The team, led by Dr. Alexis Rodriguez from NASA Ames Research Center and Planetary Science Institute, found evidence for another big meteorite impact, which triggered a second tsunami wave.
In the millions of years between the two impacts and their associated mega-tsunamis, Mars went through frigid climate change, where water turned to ice.
“The ocean level receded from its original shoreline to form a secondary shoreline, because the climate had become significantly colder,” Dr. Fairén said.
“The second tsunami formed rounded lobes of ice.”
“These lobes froze on the land as they reached their maximum extent and the ice never went back to the ocean – which implies the ocean was at least partially frozen at that time.”
Regional view of sections of circum-Chryse highland-lowland boundary region made up of Chryse and Acidalia Planitiae lowlands and Tempe, Xanthe, and Arabia Terrae highlands. The boundary is breached by the planet’s largest outflow channels (blue arrows). The red and black lines trace the margins of the two documented tsunami events. Image credit: J. Alexis P. Rodriguez et al.
“Our paper provides very solid evidence for the existence of very cold oceans on early Mars,” he said.
“It is difficult to imagine Californian beaches on ancient Mars, but try to picture the Great Lakes on a particularly cold and long winter, and that could be a more accurate image of water forming seas and oceans on ancient Mars.”
These icy lobes retained their well-defined boundaries and their flow-related shapes, suggesting the frozen ancient ocean was briny.
“Cold, salty waters may offer a refuge for life in extreme environments, as the salts could help keep the water liquid,” Dr. Fairén said.
“If life existed on Mars, these icy tsunami lobes are very good candidates to search for biosignatures.”
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J. Alexis P. Rodriguez et al. 2016. Tsunami waves extensively resurfaced the shorelines of an early Martian ocean. Scientific Reports 6, article number: 25106; doi: 10.1038/srep25106
