After the examination of the geologic shape of past shorelines through Mars' northern plains, Cornell University researchers suggest that two large meteorites hit the Red Planet millions of years apart, leading to a pair of ancient, massive tsunamis. These waves left their mark on the planet for the years after their impact and suggest that the planet harbored cold, salty oceans with the potential to harbor life.
"About 3.4 billion years ago, a big meteorite impact triggered the first tsunami wave," said Alberto Fairén, Cornell visiting scientist in astronomy and co-author of the study. "This wave was composed of liquid water. It formed widespread backwash channels to carry the water back to the ocean."
Following the discovery of the first impact, the team found evidence of yet another, which led to a second massive tsunami wave. In between these two impacts, the climate of Mars shifted, causing its water to turn into ice.
"The ocean level receded from its original shoreline to form a secondary shoreline, because the climate had become significantly colder," Fairén said.
He claims that when the second massive tsunami hit, the evidence points to the creation of 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," Fairén said. "Our paper provides very solid evidence for the existence of very cold oceans on early Mars. 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."
In addition, the well-defined boundaries of the ice and their shapes suggest that Mars' ancient frozen ocean was high in salt content.
"Cold, salty waters may offer a refuge for life in extreme environments, as the salts could help keep the water liquid," Fairén said. "If life existed on Mars, these icy tsunami lobes are very good candidates to search for biosignatures."
"We have already identified some areas inundated by the tsunamis where the ponded water appears to have emplaced lacustrine sediments, including evaporites," said Alexis Rodriguez of Cornell University and lead author of the study. "As a follow-up investigation we plan to characterize these terrains and assess their potential for future robotic or human in-situ exploration."
The findings were published in the May 19 issue of the journal Scientific Reports.
