Analysis of seismic data collected by NASA’s InSight lander suggests a vast reservoir of water. Could it be evidence of life on the Red Planet? Mars has a vast ocean of liquid water, according to a new analysis of data from NASA’s InSight lander. The now-retired instrument was launched in 2018 with a mission to record seismic activity on the planet, and quickly discovered that it was still “alive.” The new analysis is further evidence that the water didn’t evaporate when Mars lost its atmosphere billions of years ago, and isn’t confined to the polar ice caps. However, accessing this water is virtually impossible: instead of existing in a surface ocean, it’s distributed throughout layers of rock, starting at least 11 kilometers (7 miles) below the crust. Researchers at the University of California San Diego and Berkeley estimate that there’s enough liquid to create an ocean two kilometers deep across the entire planet. However, since no drilling tool on Earth can penetrate that deep, it’s unlikely that this is possible on the Red Planet. Rocks, water, and the speed of sound In the absence of the technology to drill into the Martian mantle to determine the composition of the crust and the materials it contains, scientists analyzed available seismic data collected by the InSight lander during the four years of Mars’ life. Its mission, which runs through December 2022, included records of “marsquakes” and meteorite impacts that cause surface movements, and the lander documented how fast seismic waves traveled during these events. Rock physics models were used to calculate the properties of the Martian crust as these high-speed waves passed through it. “The goal is to relate what’s inside the rock to the speed of sound,” explains geophysicist Vashan Wright of the Scripps Institution of Oceanography at the University of San Diego, who coordinated the analysis. “The denser the rock, the faster the sound travels: if there’s liquid water, it goes up, if there’s a crack, it goes down.” Rather than expect to find water beneath the surface, Wright and his colleagues took a “neutral” approach to their investigation: They expected to find anything from 0% to 100% water, or even liquid distributed between layers of the crust. InSight’s data suggests that in the distant past, all of Mars’ water moved underground, forming an aquifer similar to Earth’s. “There are deep, long-standing questions on Mars that this study helps us answer,” Wright says. “It gives us clues about the water cycle that humans have not touched.” Where is the water? Is there life? The San Diego-Berkeley group is not the first to explore the possibility of liquid water on the Red Planet. In 2022, researchers at the California Institute of Technology (Caltech) used the Mars Reconnaissance Orbiter to analyze salt deposits on Mars’ surface to calculate how much water existed until 2 billion years ago. Studies of the northern polar cap have also suggested water beneath the frozen surface. However, recent research has dismissed these conclusions as a possible misinterpretation of radar data. A decade ago, however, NASA research showed that water might occasionally flow on the surface of Mars. All of this is encouraging for scientists still searching for signs of life on Mars: Just as on Earth, liquid water is an essential ingredient for the development of life. “Water seems to be essential for life,” says Wright. “What we know about deep water is that on Earth we have life that can withstand much harsher conditions than on the surface. Finding water deep down doesn’t mean there’s life, but it’s a possibility.” Author: Matthew Ward Agius

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