Space Instrument Measures Unexpected Activity on Moon

The Swedish space instrument SARA has measured a strong and varied interaction between the Moon and solar wind, proving wrong the long-held belief that the Moon passively absorbs solar wind without affecting its surroundings, according to a researcher.

"This knowledge is of great importance to the lunar space environment which is affected both on the lunar dayside and nightside surfaces," said Charles Lue, a researcher at the Swedish Institute of Space Physics and Umea University, who analysed SARA observations as part of his PhD thesis.

The reflected solar wind ions move in spiralling tracks that can take them from the lunar dayside, where the solar wind strikes first, to the nightside of the Moon.

In local areas with strong magnetism, the solar wind flow is restricted on the surface at the same time as adjacent areas receive an increased flow.

In the long term, this has effects on the surface of the Moon and can, for instance, have an effect on the water levels in the lunar crust.

"The effects can even be seen in the form of visible light - like bright swirls imprinted on the surface of the moon," Charles Lue was quoted as saying in a Swedish Institute of Space Physics press release.

The particle instrument SARA (Sub-keV Atoms Reflecting Analyser) that was developed at the Swedish Institute of Space Physics travelled to the Moon on board the Indian satellite Chandrayaan-1.

SARA studied the solar wind interaction with the Moon in 2009, and the observations made by the instrument have since been analysed by researchers, including Charles Lue.