Taking rocks from Mars: This image shows the rock core from “Berea” inside the drill of NASA’s Perseverance Mars rover. Each core the rover takes is about the size of a piece of classroom chalk: 13 millimeters in diameter and 60 millimeters long. The rover is currently exploring different areas of Mars. It has collected a total of 19 samples. Scientists want to study Martian samples with powerful lab equipment on Earth to search for signs of ancient microbial life (微生物) and to better understand the water cycle that has shaped the surface and interior of Mars.