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More than three billion years ago, two tsunamis may have raced across a vast ocean. One lifted giant boulders and carved channels, while the other deposited big blocks of ice. Traces of these powerful events still exist — outlining a possible ocean on the planet Mars.
There’s been a lot of discussion about a Martian ocean in recent years. The elevation of most of the planet’s northern hemisphere, for example, is much lower than the southern hemisphere, suggesting that the north was once a water-filled basin. Networks of dry riverbeds seem to flow toward that basin. And studies of the water on modern Mars suggest there was much more of it on the planet in the distant past.
More support for a global ocean came from a study released a few months ago. Researchers found evidence of two ancient tsunamis. One carried boulders as big as houses far inland, and gouged deep gorges as the water retreated. And the other, which came a few million years later, after the ocean had gotten smaller and colder, dropped slabs of ice inside canyons.
The researchers say that each tsunami was created when an asteroid slammed into the ocean. The impacts generated waves that were hundreds of feet high and raced hundreds of miles inland — leaving more evidence that an ocean once covered the northern half of Mars.
Look for Mars low in the southern sky this evening, blazing like an orange star. The planet Saturn and the star Antares are off to its left.
Script by Damond Benningfield