Measuring extreme cold on surface of moon

NASA’s Lunar Reconnaissance Orbiter has created the first map of surface temperature on the moon. The news was announced at the American Geophysical Union meeting in late 2009. EarthSky spoke to planetary scientist David Paige, who oversees the lunar mission.

According to Dr. Paige, this new thermal map of the moon features the coldest temperatures in our solar system ever directly measured. He talked about the moon’s frigid north pole.

David Paige: During winter solstice at midnight, the temperature got down to 25 Kelvin in places, which is very, very cold.

Twenty-five Kelvin translates to -258 degrees Celsius, or -415 degrees Fahrenheit. Dr. Paige got these measurements from an instrument aboard the NASA orbiter called Diviner. He explained that Diviner makes temperature readings by measuring the light, or radiation, emitted from the surface of the moon.

Paige said the very coldest places on the moon are located in the crevices of large craters, which are cast in permanent shadow. These areas receive no sunlight, and very little heat from the moon’s core. In fact, Paige said that the temperatures there are the lowest ever measured in our solar system. Astronauts exploring the moon would probably want to avoid those very cold places on the map.

Dr. Paige said that before this Orbiter mission, scientists had tried to predict the temperature of the moon but they hadn’t been able to fully predict the way the lunar landscapes affect temperature.

He jokingly called Diviner “a glorified light meter.” It’s a nine-channel radiometer, which measures emitted and reflected radiation from the lunar surface.

David Paige: Diviner is the first instrument to map the temperature of the moon. Everything we are measuring is really new – we have not seen it before. We had an idea of what the thermal environment would be like, from point measurements and models, but it is a very rich diversity of elements that affect temperature. These could include things like rocks on the surface, and the nature of the soil. Particularly in the polar regions, topographical relief and the shadows that are cast by craters have a very profound effect.

Paige explained how areas of the moon get so cold.

David Paige: You can make anything cold by simply taking away any heat sources that exist. These coldest places exist in a location where basically they’re cooling off at night – except that night in these areas is indefinite. The only heat source is what scattered radiation comes off other craters and landforms in the vicinity, but no direct sunlight. And the heat flow from the inside of the moon is miniscule. So these are basically radiators that have radiated away all their energy, and are now down at very low temperatures.

Diviner’s other capability is to construct thermal images of the moon, which allow scientists to “see” the warm and cold areas of the surface of the moon in great detail.

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