Mercury

Mercury, the smallest rocky planet in the Solar System, is also the closest to the Sun. It is visible to the naked eye as a bright point in the sky, without the aid of binoculars. At first glance, Mercury resembles the Moon, although it lacks the dark "seas" seen on the lunar surface. Its terrain is dominated by many craters, ranging from small, bowl-shaped depressions to an enormous impact basin that covers nearly a quarter of the planet's surface. Deep fissures also stretch across its crust. Volcanic activity continued to shape Mercury's surface as recently as one billion years ago, but the planet has since become geologically inactive. Mercury completes one rotation on its axis every 59 Earth days. Combined with its orbital period around the Sun, this results in a solar "day" on Mercury lasting approximately 176 Earth days. Lacking an atmosphere to shield it from the Sun's intense heat during the day or to retain warmth at night, Mercury experiences extreme temperature fluctuations. Daytime temperatures can soar to 430°C, while nighttime temperatures plummet to -170°C.