What temperature is the moon?

Chris Smith answered this question from John...

Chris - The answer to this - we know this very well - because of course it's been measured directly by NASA. We heard a couple of weeks ago all about the moon landings - and things - when we celebrated the fiftieth anniversary of the first moon landing. The answer is that it matters whether you're in the sunlight or not in the sunlight because the energy reaching the Earth comes in the form of radiation from the sun. And that includes light we can see and light we can't see such as ultraviolet radiation. That energy hitting a surface like the moon's surface or an astronaut spacesuit is enough to warm it up to more than 120 degrees.

So the lit surface of the moon is at about 120 to 130 degrees C. That's why the astronauts needed such fancy spacesuits to keep their body temperature correct and reflect off a lot of that radiation. But at the same time if you go out of the illuminated part of the moon you're not having that heat hitting you anymore and the temperature plummets.

And at night-time on the moon - because the moon isn't always permanently illuminated - the night-time temperature the moon is about minus 170 degrees or even colder in some places. And so that's why people are interested in the water that's on the moon, for example, in some of these deep dark recesses because that's actually part and parcel of the material that was laid down when the moon was formed probably through a huge collision about five and a half billion years ago - about five billion years ago - four point five seven billion years ago, we think, when something clobbered the Earth and formed a fusion of two planets and our moon.

And so that material can tell us a lot about what what the Earth was made of, what that other planet was made of and therefore what the moon's also made off. But yes, very very cold - minus hundred and seventy degrees C - so certainly a chilly one.