Mercury is the planet closest to the Sun in our Solar System.
This small, rocky planet has almost no atmosphere.
Mercury has a very elliptical orbit and a huge range in temperature.
During the long daytime (which lasts 58.65 Earth days or almost an entire Mercurian year, which is 88 days long),
the temperature is hotter than an oven; during the long night (the same length), the temperature is colder than a freezer.
Mercury is about 3,031 miles (4,878 km) in diameter.
It is the smallest planet in our solar system (it used to be considered the second-smallest planet,
when Pluto was still considered to be a planet).
Mercury is a bit over one third of the diameter of the Earth. Mercury is only slightly larger than the Earth's moon.
Mercury's mass is about 3.3 x 1023 kg. This is about 1/20th of the mass of the Earth.
The gravity on Mercury is 38% of the gravity on Earth. A 100 pound person would weigh only 38 pounds on Mercury.
To calculate your weight on Mercury, just multiply your weight by 0.38.
Mercury has a huge range in temperatures. Its surface ranges in temperature from -270°F to 800°F (-168°C to 427°C).
During the very long daytime (88 Earth-days long), the temperatures are very high
(the second-highest in the Solar System - only Venus is hotter); during the long night, the thin atmosphere lets the heat dissipate, and the temperature drops quickly.