Seasonal Dark Streaks (Recurring Slope Lineae)

Seasonal dark streaks, known as Recurring Slope Lineae (RSL), are intriguing Martian features that appear and fade with temperature changes. These narrow, dark lines flow down steep slopes during warmer months, suggesting possible liquid water activity just below the surface. First identified in 2011, RSL remain one of Mars' most compelling potential biosignatures, as liquid water could support microbial life. While some scientists attribute them to dry sand flows or briny water, their seasonal behavior continues to fuel speculation about underground aquifers. These mysterious streaks represent our best clues in the ongoing search for present-day life on the Red Planet.