The smallest planet and closest to the Sun, Mercury is a heavily cratered rocky world with virtually no atmosphere. Despite its proximity to the Sun, it is not the hottest planet — Venus is — because it has no atmosphere to trap heat.
| Mission | Year | Notes |
|---|---|---|
| Mariner 10 | 1974–1975 | First spacecraft to visit Mercury; 3 flyby passes |
| MESSENGER | 2004–2015 | First to orbit Mercury; mapped the entire surface |
| BepiColombo | 2018–2025 | ESA/JAXA mission, arrival planned 2025 |
Images courtesy of NASA Image & Video Library. All images are public domain.
Images courtesy of NASA Image & Video Library. All images are public domain.