Fig. 4: The satellite-based magnetic field model (L19) and areas influenced by measurements.

a–d, Maps of the horizontal magnetic field strength in the Zhurong landing region predicted by the L19 model¹⁴ downwards continued to four different heights of h = 150 km (a), 100 km (b), 50 km (c) and 0 km (d). The corresponding field strength at the Zhurong landing site (25.066° N, 109.926° E; star) is approximately 2.6 nT at h = 150 km, 5.6 nT at h = 100 km, 16.2 nT at 50 km and 55.1 nT at the Martian surface. The black circle at h = 0 km denotes the approximate ground area averaged by the orbital model with a radius of 150 km. It includes some of the stronger anomalies. The corresponding circle for Zhurong’s ground measurement, assuming a magnetized layer of depth 1 km, is too small to be shown on this scale. The grey curve indicates the topography boundary of Utopia Basin at the surface altitude.