Megatsunami on Mars linked to an asteroid strike 3.4 billion years ago

The new study published in the journal Scientific Reports analyzed "maps of Mars’ surface, created by combining images from previous missions to the planet, and identified an impact crater that could have caused the megatsunami," as mentioned in the press release.

The Pohl mystery

The diameter of the crater — named Pohl — caused by the impact of the asteroid, is estimated to be around 68.4 miles (110 kilometers). The area of the impact, which was identified to have happened in an area known as Chryse Planitia, north of the Martian equator, is believed to have been an ocean in the past.

Various simulations conducted based on the diameter of the crater led scientists to infer that craters with similar dimensions to Pohl were caused by either a nine-kilometer asteroid, encountering strong ground resistance that released 13 million megatons of TNT energy, or a three-kilometer asteroid encountering weak ground resistance, releasing 0.5 million megatons of TNT energy.

For reference, the most powerful nuclear bomb test in the world, Tsar Bomba, delivered 57 megatons of TNT energy.

The aftermath of the megatsunami

The simulations carried out by the team with the given values triggered a tsunami with waves that measured 250 meters in height and impacted areas as far as 932 miles (1500 kilometers) from the epicenter.

"Notably, the seismic shaking associated with the impact would have been so intense that it could have dislodged sea floor materials into the megatsunami, densifying some wave fronts into run-up debris flows," Rodriguez said in a statement. The next step for the team will be to "characterize Pohl as a landing site to investigate how the ocean chemistry evolved, its habitability, and a possible geologic record containing evidence of current or extinct life evidence," Rodriguez said.

Study Abstract:

In 1976, NASA's Viking 1 Lander (V1L) was the first spacecraft to operate successfully on the Martian surface. The V1L landed near the terminus of an enormous catastrophic flood channel, Maja Valles. However, instead of the expected megaflood record, its cameras imaged a boulder-strewn surface of elusive origin. We identified a 110-km-diameter impact crater (Pohl) ~ 900 km northeast of the landing site, stratigraphically positioned (a) above catastrophic flood-eroded surfaces formed ~ 3.4 Ga during a period of northern plains oceanic inundation and (b) below the younger of two previously hypothesized megatsunami deposits. These stratigraphic relationships suggest that a marine impact likely formed the crater. Our simulated impact-generated megatsunami run-ups closely match the mapped older megatsunami deposit's margins and predict fronts reaching the V1L site. The site's location along a highland-facing lobe aligned to erosional grooves supports a megatsunami origin. Our mapping also shows that Pohl's knobby rim regionally represents a broader history of megatsunami modification involving circum-oceanic glaciation and sedimentary extrusions extending beyond the recorded megatsunami emplacement in Chryse Planitia. Our findings allow that rocks and soil salts at the landing site are of marine origin, inviting the scientific reconsideration of information gathered from the first in-situ measurements on Mars.