A new study led by the Scripps Institution of Oceanography at the University of California, San Diego, has shown that Mars still has a large amount of liquid water in addition to the frozen water at its poles. This study provides the strongest evidence of the Martian ocean to date, and if its conclusions are true, it will lay the foundation for further exploration of the planet's habitability and the search for extraterrestrial life. The research results were published on the 12th in the Proceedings of the National Academy of Sciences in the United States. For decades, the existence of liquid water on Mars has been attracting scientists. This is because water is crucial for the livability of planets. This time, the research team analyzed data collected during the four-year mission of NASA's Insight Mars lander. The lander collected variable information such as the velocity of Martian seismic waves from the ground directly below it, and scientists inferred what substances exist beneath the surface based on this. The team adopted a rock physics mathematical model. This model is the same as the one used to draw underground aquifers and oil fields on Earth. The results showed that these data were best explained by deep fractured igneous rocks filled with liquid water, and the amount of water was enormous - the team estimated that the amount of groundwater could cover the entire planet at depths of 1-2 kilometers. This new 'reservoir' is not suitable for providing a water source for future Mars settlements, as it is located in tiny cracks and pores in the rocks in the middle of the Martian crust, at a distance of 11.5-20 kilometers from the Martian surface. Even on Earth, drilling such a deep hole is still a challenge. However, this discovery has identified a promising location for searching for life on Mars and also helps answer questions about the geological history of Mars. Understanding the water cycle on Mars is crucial for understanding its climate, surface, and internal evolution. At present, a large amount of evidence supports the hypothesis that water once flowed on the surface of Mars. But that 'wet era' ended over 3 billion years ago. The new discovery suggests that these waters did not escape into space, but instead infiltrated into the Earth's crust. The main mission of InSight is to investigate the crust, mantle, core, and atmosphere of Mars, and it has recorded valuable information about the interior of Mars before the end of its mission in 2022. The location of this analysis is below the lander, and the team believes that assuming the entire crust of Mars is similar, Mars has much larger oceans than previously assumed. (New Society)