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

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

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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 from the ground showed a surprising boulder-strewn surface in the northern equatorial region of the red planet, rather than the smooth plains and floodplains expected from images of the area from space.

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

Now new research suggests the lander touched down 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 slammed into the shallow ocean of Mars — similar to the Chicxulub asteroid impact which, according to researchers, wiped out dinosaurs on Earth 66 million years ago.

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

Interest in the potential for life on the red planet led scientists to select the northern equatorial region, Chryse Planitia, as the first Mars landing site for Viking I.

“The lander was designed to look for evidence of existing life on the surface of Mars, so to select a suitable landing site the engineers and scientists at the time faced the arduous task of using some of the earliest images obtained of the planet. , accompanied by Earth-based imagery.” radar probe from the surface of the planet,” lead study author Alexis Rodriguez, a senior scientist at the Planetary Science Institute in Tucson, Arizona, said via email.

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

Viking 1 captured this image on August 21, 1976, looking south about 15 minutes before sunset on Mars.

At first, scientists thought the rocky surface might be a thick layer of debris left behind as a result of space rocks colliding with Mars, creating craters or broken pieces of lava.

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

“Our research offers a new solution — that a megatsunami washed up and deposited sediments on which the Viking 1 lander landed about 3.4 billion years later,” Rodriguez said.

The researchers think the tsunami occurred when an asteroid or comet hit the planet’s northern ocean. But finding a resulting impact crater was difficult.

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

The crater is 68 miles (nearly 110 kilometers) wide in part of the northern lowlands — an area that was once likely covered by the ocean. Researchers simulated collisions in this region using models to determine what impact was needed to create the so-called Pohl crater.

It was possible in two different scenarios, one caused by a 5.6-mile (9-kilometer) asteroid experiencing strong ground drag and releasing 13 million megatons of TNT energy, or a 1.8-mile (2.9-kilometer) asteroid plowing into softer ground and causing 0.5 million megatons of TNT energy is released.

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

During 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-long asteroid spawned a tsunami that was 800 feet (250 meters) high when it reached land.

The results were similar to those of the Chicxulub impact on Earth, which created a crater that was initially 100 kilometers wide and caused a towering tsunami that traveled around the world.

The impact likely sent water vapor into the atmosphere, which would have affected the Martian climate and possibly caused snow or rain in the precipitation. Large amounts of water from the shallow ocean, as well as sediments, would have been displaced, Rodriguez said, although most of the water returned to the ocean soon after the megatsunami peaked.

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

It is also possible that the megatsunami reached the site of the 1997 landfall for the scoutsouth of where Viking 1 landed, even contributing to the formation of an inland sea.

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

“The ocean is believed to have been fed by groundwater from aquifers that likely formed much earlier in Mars’ 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 the Pohl crater as a possible landing site for a future rover, as the site may contain traces of ancient life.

“Immediately after its formation, the crater would have generated submarine hydrothermal systems that lasted for tens of thousands of years and provided energy and nutrient-rich environments,” Rodriguez said, referring to the heat generated by the asteroid impact.



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