Mercury is so cold despite being close to the Sun due to the lack of a significant atmosphere. Without a substantial atmosphere to retain heat, Mercury’s surface temperature fluctuates considerably. During the day, the side facing the Sun can become extremely hot, but at night, temperatures drop sharply because there is no atmosphere to retain the heat. This causes extreme temperature variations between day and night.
Proximity to the Sun affects Mercury primarily in terms of surface temperatures and orbital dynamics.
Although Mercury is closer to the Sun than to Earth, it experiences large temperature fluctuations due to its thin atmosphere. Proximity to the Sun means Mercury receives more solar energy, but without a thick atmosphere to retain this heat, it cannot maintain consistently high temperatures.
Mercury is not uniformly hot because its surface temperature varies greatly. Even though it is very hot on the side facing away from the Sun, the lack of atmospheric insulation means that the temperature can drop significantly on the side facing away from the Sun.
This results in a wide temperature range between day and night.
Space is cold despite the presence of the Sun because space itself is almost empty and does not conduct heat. The temperature in space is determined by the amount of energy an object absorbs or radiates. Without an atmosphere to transfer heat, objects in space can experience temperature extremes due to their exposure to solar radiation and their own radiative cooling.
On the side of Mercury closest to the Sun, temperatures can reach around 800 degrees Fahrenheit (427 degrees Celsius).
This is because Mercury’s surface absorbs a significant amount of solar energy, making it one of the hottest surfaces in the solar system during the day. However, this extreme heat is only present on the side exposed to the Sun; the temperature on the dark side can drop to around -330 degrees Fahrenheit (-200 degrees Celsius).