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When NASA’s Viking 1 lander made history on July 20, 1976 as the first spacecraft to land on Mars, it sent back images of a sight no one expected.
The first ground-based images there showed a strikingly rocky 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 baffled scientists who believed an ocean existed there.
New research suggests that the lander landed where the Martian megatsunami deposited materials 3.4 billion years ago, according to a study published Thursday in the journal. Scientific Reports.
The catastrophic event probably occurred when an asteroid crashed into the shallow Martian ocean. Chicxulub asteroid impact According to researchers, it wiped out the dinosaurs on earth 66 million years ago.
Five years before the Viking I landing, NASA’s Mariner 9 spacecraft orbited Mars and saw the first sights on another planet that showed ancient flood channels there.
Interest in the potential for life on the red planet led scientists to choose its northern equatorial region, Chryse Planitia, as the first Mars landing site for Viking I.
“The lander was designed to look for evidence of life on the surface of Mars, so to choose a suitable landing site, engineers and scientists at the time faced the difficult task of using the earliest images of the planet. a radar survey of the planet’s surface,” lead author Alexis Rodriguez, a senior scientist at the Planetary Science Institute in Tucson, Arizona, said via email.
“The choice of the landing site was necessary to fulfill a critical requirement – the presence of extensive evidence of past surface water. Life on Earth has always required the presence of water.”
At first, scientists thought the rocky surface might be a thick layer of debris left behind by space rocks crashing into Mars and leaving behind craters or pieces of broken lava.
However, there were not enough craters nearby, and pieces of lava were rarely found in the area.
“Our study offers a new solution – that a megatsunami hit the coast, depositing the sediments that the Viking 1 lander landed on about 3.4 billion years later,” said Rodriguez.
Researchers believe that the tsunami occurred when an asteroid or comet hit the planet’s northern ocean. However, it was difficult to find the impact crater as a result.
Rodriguez and his team studied maps of the Martian surface from various missions and analyzed a newly identified crater that appeared to be a likely impact site.
The crater is 68 miles (about 110 kilometers) wide in a part of the northern plain – an area once covered by the ocean. The researchers used modeling to simulate impacts in this region to determine what impact was needed to create what is known as Pohl Crater.
This was possible in two different scenarios, either a 5.6-mile (9-kilometer) asteroid resisting the strong earth and releasing 13 million megatons of TNT energy, or a 1.8-mile (2.9-kilometer) asteroid plowing into a softer earth and 0.5 releases a million megatons of TNT energy.
For perspective, the most powerful nuclear bomb ever tested, Tsar BombaIt created 57 megatons of TNT energy.
In the simulations, both impacts produced a Pohl-sized crater as well as a megatsunami that reached 932 miles (1,500 kilometers) from the impact site.
After the 1.8-mile asteroid hit land, it created a 250-meter-tall tsunami.
The results were similar to the Chicxulub impact on Earth, which initially created a crater 62 miles (100 kilometers) wide. caused a powerful tsunami that traveled around the world.
The impact likely sent water vapor into the atmosphere, which could have affected the Martian climate and produced snow or rain in the rain. A large amount of water, as well as sediment, would have been displaced from the shallow ocean, although most of the water returned to the ocean after the peak of the megatsunami, Rodriguez said.
“The seismic upheaval associated with the impact would have been so strong that it could have released seafloor materials into a megatsunami,” said study co-author Darrel Robertson of NASA’s Ames Research Center in Silicon Valley, California.
Perhaps the megatsunami reached the landfall site in 1997 PathfinderSouth of the landing site of Viking 1 and even contributed to the formation of the inland sea.
If so, then the two landers landed on an ancient marine environment.
“The ocean is thought to have been fed by groundwater, which probably formed earlier in Mars’ history – 3.7 billion years ago – when the planet became ‘Earth-like’ with rivers, lakes, seas and a primordial ocean,” Rodriguez said.
Next, the team wants to explore Pohl Crater as a potential landing site for a future rover, as it may contain evidence of ancient life.
“Immediately after creation, the crater would have created underwater hydrothermal systems that would have lasted for tens of thousands of years, providing environments rich in energy and nutrients,” Rodriguez said, referring to the heat generated by the asteroid’s impact.