Viking 1 may have landed at the site of the ancient Martian megatsunami

Subscribe to CNN’s Wonder Theory Science Newsletter. Explore the universe with news about fascinating discoveries, scientific advances and more.

CNN
—

When NASA’s Viking 1 lander made history as the first spacecraft to land on Mars on July 20, 1976, it sent back images of a landscape no one expected.

Those first images taken from the ground there showed a surprisingly rock-strewn surface in the red planet’s northern equatorial region, rather than the smooth plains and flood channels expected from images of the area taken from space.

The mystery of the Viking landing site has long puzzled scientists, who believe there was once an ocean.

Now, new research suggests the lander landed where a Martian megatsunami deposited materials 3.4 billion years ago, according to a study published Thursday in the journal. Scientific reports.

The catastrophic event likely occurred when an asteroid crashed into the shallow Martian ocean, similar to the Impact of the asteroid Chicxulub that wiped out the dinosaurs from Earth 66 million years ago, according to researchers.

Five years before the Viking I landing, NASA’s Mariner 9 spacecraft had orbited Mars, discovering the first landscapes on another planet that suggested evidence of ancient flood channels there.

Interest in the potential for life on the Red Planet prompted scientists to select its northern equatorial region, Chryse Planitia, as the first Martian landing site for Viking I.

“The lander was designed to search for evidence of life existing on the Martian surface, so in order to select a suitable landing site, engineers and scientists at the time faced the arduous task of using some of the first images acquired of the planet, accompanied by images based on Earth. radar probing of the planet’s surface,” said lead study author Alexis Rodriguez, senior scientist at the Institute of Planetary Sciences from Tucson, Arizona, by email.

“The selection of the landing site needed to meet a critical requirement: the presence of extensive evidence of ancient surface water. On Earth, life always requires the presence of water to exist.”

At first, scientists thought the rocky surface might be a thick layer of debris left behind by space rocks crashing into Mars and creating craters or broken pieces of lava.

But there weren’t enough craters nearby, and lava fragments turned out to be rare on the ground at the site.

“Our research provides a new solution: that a megatsunami washed ashore, depositing sediments on which, about 3.4 billion years later, Viking 1 landed,” Rodriguez said.

Researchers believe the tsunami was caused when an asteroid or comet hit the planet’s northern ocean. But finding a resulting impact crater has been difficult.

Rodriguez and his team studied maps of the Martian surface created from different missions and analyzed a newly identified crater that appeared to be the likely point of impact.

The crater is 68 miles (nearly 110 kilometers) into part of the northern lowlands, an area that was once probably covered by ocean. The researchers simulated collisions in this region using modeling to determine what impact was necessary to create what is known as Pohl Crater.

It was possible in two different scenarios, one caused by a 5.6-mile (9-kilometer) asteroid that met strong ground resistance and released 13 million megatons of TNT energy, or a 1.8-mile (2 .9 kilometers) that plowed into softer ground and released 0.5 million megatons of TNT energy.

For perspective, the most powerful nuclear bomb ever tested, Tsar Bombait created 57 megatons of TNT energy.

During the simulations, both impacts created a crater the size of Pohl, as well as a megatsunami that reached 932 miles (1,500 kilometers) from the impact site.

The 1.8-mile asteroid generated a tsunami that measured 820 feet (250 meters) high once it hit the ground.

The results were similar to the Chicxulub impact on Earth, which created a crater that was initially 62 miles (100 kilometers) in diameter and it caused a huge tsunami that traveled around the world.

The impact likely sent water vapor into the atmosphere, which would have affected the Martian climate and potentially created snow or rain in precipitation. Large amounts of shallow ocean water, as well as sediment, would have been displaced, Rodriguez said, although most of the water returned to the ocean shortly after the megatsunami reached its peak

“The seismic shaking associated with the impact would have been so intense that it could have dislodged materials from the seafloor in the megatsunami,” said study co-author Darrel Robertson at NASA’s Ames Research Center in Silicon Valley, California, in a statement

It is also possible that the megatsunami reached the location of the 1997 landfall Pathfindersouth of where Viking 1 landed, and even contributed to the formation of an inland sea.

If so, the two landers landed on the site of the ancient marine environments.

“The ocean is thought to have been fed groundwater from aquifers that likely formed much earlier in Marcia’s history, more than 3.7 billion years ago, when the planet was ‘Earth-like “with rivers, lakes, seas and a primordial ocean”. Rodriguez said.

Next, the team wants to investigate Pohl Crater as a possible landing site for a future rover, as the location could contain evidence of ancient life.

“Ever since its formation, the crater would have generated underwater hydrothermal systems tens of thousands of years old, providing energy and nutrient-rich environments,” Rodríguez said, referring to the heat generated by the impact of the asteroid