Each day we feature a different image or photograph of our fascinating universe, along with a brief explanation written by a professional astronomer. Mercury , the closest planet to the Sun , has a surface with so many craters it resembles the Earth 's Moon . The largest surface feature on Mercury is the Caloris Basin, which resulted from a collision with an asteroid . The basin, which is more that 1000 kilometers across, is visible as the large circular feature at the bottom of the above photograph. Similar features, such as the Mare Orientale , are seen on the Moon.
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