Martian Tremors Provide Strongest Evidence Yet of Liquid Water

NASA’s InSight lander may have retired over a year ago, but the data it sent back to Earth, specifically the seismic speeds of marsquakes, could contain the best evidence yet of liquid water on Mars.

NASA launched InSight, also known as Interior Exploration using Seismic Investigations, Geodesy, and Heat Transport, in 2018 to study the deep interior of Mars. Its four-year mission came to an end in December 2022 but analysis of the data it collected remains ongoing.

In a study published August 12 in the journal Proceedings of the National Academy of Sciences, a team of researchers from UC San Diego’s Scripps Institution of Oceanography, led by geophysicist Vashan Wright, concluded that InSight’s data indicates the presence of liquid water in the Martian crust.

“Understanding the Martian water cycle is critical for understanding the evolution of the climate, surface, and interior,” said Wright in a press release. “A useful starting point is to identify where water is and how much is there.”

Wright and his team did not just look at the chemical composition of the dirt directly below InSight. Wanting to peer deeper into Mars’ interior, they analyzed data on marsquakes—the seismic activity that regularly shakes up the Red Planet. The speed at which these quakes travelled allowed the team to infer which substances are present beneath the surface. The best explanation for the data was that liquid water is present within the crust. They acknowledged that the findings are not definitive, but highlighted the need to further study Mars’ mineralogy.

Decades of evidence show that both Mars’ north and south poles are covered in frozen water, including a massive reservoir in the north that lies 1.2 miles (2 kilometers) below the surface. Because Mars’ atmosphere is far thinner than Earth’s, fresh liquid water turns to gas more easily. However, if the water is extremely salty, the boiling level would lower, allowing it to stay liquid for longer. A 2016 paper concluded dark streaks on the Martian surface may be formed by water running downhill.

If Wright’s team is correct, it could have big implications for the theory that Mars was once home to microbial life. That theory got a big boost recently, thanks to the Perseverance rover’s discovery of a very strange rock. The presence of liquid water would also be a huge plus for any crewed missions to the planet. More research is needed; hopefully future missions, whether crewed or uncrewed, will get to the bottom of this very important unanswered question.