NASA's Perseverance Mars rover has uncovered evidence that a 245-foot-thick (75-meter-thick) stack of ancient rock on the rim of Jezero Crater was built by repeated asteroid impacts. Referred to as the "Broom Point member" by the rover's science team, this sequence of layered bedrock is likely more than 3.9 billion years old, making it among the oldest terrain ever examined by a Mars rover.