A Japanese craft has sniffed the moon’s whiff of an atmosphere, and has confirmed that it comes largely from sunlight brutally hammering the lunar surface.
The atmosphere of the moon, which is so thin, is referred to as an exosphere.
According to a report in Discovery News, using the very first direct measurements of the moon’s “exosphere” as the moon passed through the streaming tail of Earth’s protective magnetic field, researchers were able to watch the short-lived and ever-changing exosphere in the absence of the hot, magnetized solar wind.
What they found confirmed that it’s really just powerful ultraviolet light knocking beat-up atoms, or ions, off the lunar surface and manufacturing the bulk of the weak lunar perfume. When the moon passed inside of the tail of Earth’s magnetic field, which streams off the Earth like a gigantic windsock whipping in the solar wind, the moon’s surface was protected for about four days from solar wind, but not from sunlight. So, if the hot-particle-laden solar wind was the culprit in making the exosphere, the Japanese spacecraft SELENE should have seen a noticeable drop in the exosphere ions. But that’s not what the Japanese research team saw.
“The ion fluxes were higher when the sun was higher, which is consistent with the idea that the solar photon-driven processes dominates,” according to Japan Aerospace Exploration Agency’s Takaaki Tanaka, the lead author of the report. In other words, powerful ultraviolet light photons are big-time exosphere-makers.
This discovery is important for several reasons, explained NASA lunar scientist Menelaos Sarantos. One is that it could help interpret what kinds of minerals are on the moon’s surface.
“What comes out (as exosphere) more or less tells you the mineralogy of the surface,” Sarantos said.
The ions and how they change over time also provide direct evidence of how much of a beating the lunar surface is taking, which is invaluable information for anyone hoping to house humans on the moon in the future.
“If you want to build a lunar base or put humans on the surface for any time, you want a well—defined radiation environment,” Sarantos said.