Due to its small size, most of its core has cooled and solidified. Instead, the heat on Mercury is primarily generated by sunlight. Its lack of an appreciable atmosphere causes extreme differences in surface temperatures between day and night. During the day, surface temperatures can soar up to 450 degrees Celsius (842 degrees Fahrenheit), making it incredibly hot due to direct sunlight.
At night, the absence of an insulating atmosphere allows heat to escape rapidly into space, causing temperatures to drop sharply and reach lows of −180 degrees Celsius (-292 degrees Fahrenheit).
