Perseverance’s radar revealed ancient subsurface river delta on Mars

NASA's Perseverance rover, which touched down in Jezero Crater in 2021, has been on a quest to uncover the secrets of a once-thriving Martian lakebed. Central to this mission is the striking Western Delta, a geological marvel formed by a river that flowed into the basin billions of years ago. Recently, the rover's ground-penetrating radar, known as RIMFAX, has identified what appears to be an even older river delta, lying buried several meters below the surface. "This discovery is a significant opportunity to search for potential biosignatures at depth," stated Emily L. Cardarelli, an astrobiologist at UCLA and leader of the RIMFAX interpretation team. The RIMFAX, or Radar Imager for Mars Subsurface Experiment, continuously emits radar waves into the Martian soil, collecting data every 10 centimeters the rover travels. When these waves encounter different geological boundaries, such as rock or sediment layers, some signals are reflected back. By analyzing the timing and strength of these reflections, scientists can create detailed vertical profiles of the Martian crust, akin to a sonogram. From September 2023 to February 2024, spanning more than 250 Martian sols, Perseverance traversed a geologically rich area known as the Margin unit. This expansive deposit, located between the western fan deposits and the crater’s rim, is abundant in magnesium carbonates. These carbonates were a key factor in selecting Jezero Crater as the rover's landing site, as they are known to preserve vital chemical evidence of past life on Earth. "Consider the Cliffs of Dover, which are primarily composed of carbonate and hold numerous fossils," Cardarelli remarked, drawing parallels to the importance of these materials in understanding life on Mars.