Mariner 10 was the only spacecraft to ever approach it, so less than half of its surface has been mapped.
Mariner 10 was the only spacecraft to ever approach it, so less than half of its surface has been mapped. Even so, a good deal about its environmental conditions are known, such as the lack of atmosphere and extreme temperature variation, ranging from -180°C at night to 430°C in the day. For ten points, which planet recently became the smallest in our solar system due to a decision by the International Astronomical Union?
Mariner 10 was the only spacecraft to ever approach it, so less than half of its surface has been mapped.
{Mercury}