The Great Martian Mystery For decades, the primary question for planetary scientists has been: Where did the water go? We see the ancient riverbeds and dried-up lake basins on the surface, but the current atmosphere is too thin to hold liquid water. While some escaped into space, a new study suggests a massive amount stayed behind—just out of sight. Deep Crustal Reservoirs Using data from the InSight lander, researchers analyzed "marsquakes" to map the planet's interior. They found evidence of a "mid-crustal" layer between 10 and 20 kilometers deep that is saturated with liquid water. On Earth, groundwater infiltration from the surface is a common process. It appears this occurred on Mars during its wetter youth." Could Life Exist There? While this water is likely trapped in tiny cracks and pores within volcanic rock, its existence changes the game for Astrobiology. On Earth, deep microbial life exists far underground where conditions are stable. If Mars has liquid water and internal heat, the ingredients for life might still be present today, miles beneath the frozen desert. The Catch Don't pack your bags for a Martian well-digging expedition just yet. Drilling 10 kilometers deep on Earth is a massive engineering feat; doing it on Mars is currently impossible with our existing technology. However, knowing the water is there provides a definitive map for where future robotic missions should look for signs of life.