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Figure 1. Magnetic scan of a slice of ALH84001, superimposed on its optical image. Intensity of the perpendicular component of the magnetic field is depicted with a red and blue color scale (corresponding to field lines oriented out-of-the-page and into-the-page, respectively). Note the large magnetic anomaly centered on the fusion crust, and the baked zone that extends less than a few mm inwards from it. The center of the rock has a heterogeneous magnetic pattern, indicating that it has not been heated even to 40ºC since before 15 Ma (Weiss et al. 2000). This implies that rocks can travel between Mars and Earth without being heat sterilized.