Extended Data Fig. 6: The satellite-based magnetic field model (L19) and areas influenced by measurements.

Panels (a-d) show maps of the horizontal intensity in the Zhurong landing region predicted by the L19 model⁶ downward continued to four different heights h = 150 km, 100 km, 50 km, 0 km. The corresponding vertical field strength at the Zhurong landing site (25.066° N, 109.926° E, the stars) is approximately 4.8 nT at h = 150 km, 9.2 nT at h = 100 km, 21.3 nT at 50 km, and 57.1nT at the Martian surface. The black circle at h = 0 km denotes the approximate ground area averaged by the orbital model, radius 150 km. It includes some of the stronger anomalies. The corresponding circle for Zhurong’s ground measurement, assuming a magnetised layer of depth 1 km, is too small to be shown on this scale. The gray curve indicates the topography boundary of Utopia basin at the surface altitude.