Mercury rotates relatively slowly, so its night side spends a lengthy period in the dark, protected from the sun; during those times, the temperature drops to barely 100 Kelvin (-173 degC or -280 degF). That low temperature is very frigid, considerably below any known naturally occurring temperature on Earth. However, because of its distance from the Sun (52 million km or 32 million miles), Mercury has only 0.5% of the sunlight that reaches Earth, so its average surface temperature is similar to that of Earth's at 60°N.
Earth's moon has no atmosphere and is always dark enough for its coldest temperatures to be reached, but it still gets heat from the planet it orbits. So too does Mercury have a cold interior even though it has no atmosphere. The inner planets probably formed near the same time as the solar system did, with Jupiter moving out to become more massive than Earth while leaving her frozen inside behind its gas cloud, Venus as a hot molten planet, and then Earth as a cold ball of rock and ice.
They all had their initial heat from the gravitational energy released when they formed from the dust and gas swirling around within the newborn solar system. But only Earth and Mercury remain warm enough for water to currently exist as liquid. The rest of the moons may once have had oceans, but they're long since gone.
Mercury's dark side is that it is extremely cold since it has practically no atmosphere to hold in heat and keep the surface warm. Temperatures can fall below -300 degrees Fahrenheit. The bases of several craters near Mercury's poles are never illuminated by sunlight. These areas must be significantly colder than the rest of the planet.
However, due to its proximity to the Sun, some parts of Mercury get heated up to about 150 degrees Farenheit. The center of the planet is quite hot for its size (about 600 degrees F), which is why they have been explored by spacecraft equipped with thermometers.
The Sun heats Earth through photosynthesis, but because Mercury has no atmosphere this process does not occur. Instead, the radioactivity of mercury is responsible for its internal heat source. Radioactive elements such as potassium and uranium decay over time, releasing energy that keeps the planet warm. Although less than Earth, Mercury's average temperature is high enough to melt lead.
Although it is the closest planet to the Sun, Mercury has no influence on Earth's climate. The only reason we know anything about it is because NASA has sent several missions there over the years.
The temperature is 800 degrees Fahrenheit. Mercury's temperatures are quite high. During the day, surface temperatures can approach 800 degrees Fahrenheit (430 degrees Celsius). Because there is no atmosphere to keep the heat in, nighttime temperatures on the planet's surface can reach minus 290 degrees Fahrenheit (minus 180 degrees Celsius).
All things considered, it is a very warm planet!
However, even though it is one of the hottest planets in the solar system, life as we know it could never develop on Mercury because the severe thermal changes would destroy any living organisms that formed.
The temperature on Mercury fluctuates greatly over time. The planet's orbit around the Sun is eccentric, which means its distance from the Sun varies between 39.5 million miles (64 million km) at its closest point and 483 million miles (791 million km) at its farthest. This causes differences in climate across the planet. The far-away part of the planet experiences great coldness due to less sunlight reaching it, while the close-by portion heats up due to more sunlight exposure.
The temperature on Mercury is so high that any organic compound will be destroyed within minutes or seconds. All things considered, mercury is a very hostile planet for any form of life as we know it!
The surface temperature of Mercury reaches a blistering 430 degrees Celsius [800 degrees Fahrenheit] during the day and plummets to -180 degrees Celsius [-290 F] at night in the absence of an atmosphere. As a result, its surface conditions have been appropriately removed from scientific consideration as a probable host of life.
However, even with this disadvantage, scientists believe that Mercury may be fully or partially covered by a thin veneer of ice that interacts with the sun each time it passes over a north-south line called a "mercurian" meridian. This ice would reflect some sunlight back out into space and probably lower the average surface temperature of Mercury to around 40 degrees Celsius [80 degrees Fahrenheit]. The MERCs (Mercury Earth Relay Network) were proposed in 1992 to provide near-real-time communication between Earth and astronauts on board the Space Shuttle or future Mercurians. If such a mission were ever undertaken, the vehicles would be equipped with radio telescopes mounted on spinning axes so that they could constantly scan the skies for signals from Mercury.
Scientists have also suggested that water may be trapped in porous rock under the planet's crust. Although the rock would be extremely hot under normal conditions, there are many locations where seismic activity causes volcanic eruptions which bring water vapor into the air, forming a greenhouse effect similar to that of Venus.
Why does Mercury have a wider temperature range than any other planet? Because it is so near to the sun, the temperature may reach 430 degrees Celsius throughout the day. Because there is no atmosphere, heat escapes at night, causing temperatures to drop below -170 degrees Celsius.
Mercury has the most eccentric orbit of all the planets, which means that it takes 87.9 days to go around the sun. This is because it is closest to the sun in perihelion (the point in its orbit when it is nearest to the sun) and farthest from the sun in aphelion (its point of remotest distance from the sun). In between, it passes through all phases of the moon.
This close proximity to the sun makes it too hot for liquid water to exist on its surface. However, it is possible that liquid water may be present under the extreme cold conditions that occur at night!
The Earth's average temperature is 15 degrees Celsius. Although this is not a very high temperature, you can imagine how low it gets on Mercury! The lowest temperature ever measured on Earth was -89.2 degrees Celsius, and the solar wind makes things even colder there. It is estimated that if Mercury had an atmosphere like Earth's, the average temperature would be 3 degrees Celsius lower.
There are two reasons why Venus has such high temperatures.