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The climate of Mercury is one of extremes. One moment you would be struggling to stay warm and could be exploring the ice at the bottom of a crater, then as the Sun rises you would begin to be comfortable, but do not relax. That feeling will only last a few minutes. As the Sun illuminates the dayside of the planet, temperatures will begin to rise to an amazing 700°K. That is a 600°K swing from night time temperatures.
There are many factors that can affect the climate of Mercury and other planets. In addition to temperature, humidity, atmospheric pressure, wind, rainfall and many other factors come into play. Atmospheric pressure on Mercury has been estimated to be 0.000000000002 kg/cm2. For comparison, the air pressure on Earth is 1.03 kg/cm2 or 515 billion times higher than Mercury’s. That is still quite a bit of pressure considering that Mercury’s atmosphere is very tenuous. It is more of an exosphere than a true atmosphere. It is a thin collection of particles that are regenerated from the planet’s surface and interactions with the solar wind. It is constantly being generated, but then blown away by the solar wind. AS for rainfall, there is none. While there is some water vapor in the exosphere, it never returns to the surface and is not significant enough to create measurable humidity. The only wind on the planet is from the solar wind. It is deflected to some extent by the magnetosphere. The magnetosphere/solar wind interaction is thought to generate magnetic tornadoes above the surface of the planet.
Scientists hope to gain more knowledge about the planet’s climate from data returned by the MESSENGER spacecraft. They also hope that any new information can be verified and expanded upon by the BepiColumbo mission that will be launched by the European Space Agency in 2014.
Overall, what you would find if you were experiencing the climate of Mercury is a dry dead world, where you would constantly be trying to stay within the terminator boundary between the dark and light sides of the planet in order to optimize your chances of survival.
We have written many stories about Mercury here on Universe Today. Here’s an article about a the discovery that Mercury’s core is liquid. And how Mercury is actually less like the Moon than previously believed.
We have also recorded a whole episode of Astronomy Cast that’s just about planet Mercury. Listen to it here, Episode 49: Mercury.