This is a mosaic of the caloris basin and its surrounding area. The Caloris Basin is closest to the sun when Mercury is at the closest point in its orbit to the sun.
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NASA

The Caloris Basin

The Caloris Basin is the largest feature on the surface of Mercury. This crater was formed by the impact of a large meteorite near the end of the period of frequent impact cratering in the early solar system. We only know what half of the crater looks like, because the other half was in darkness when Mariner 10 flew by the planet. Surrounding the impact site are concentric ridges within relatively smooth plains probably brought about by renewed volcanic activity which started after the impact. On the other side of the planet, directly across from the basin, is a region initially described as the "weird" terrain, where a chaotic mix of hills and fractures is present. This may have been produced in response to shock waves which traveled to this point on the surface following the Caloris Basin impact.

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