Strange bright patterns on the moon鈥檚 surface called lunar swirls don鈥檛 seem to be simply draped across the ground, as researchers thought, but instead correlate with topographical changes. This means they may be more complicated than we realised.
The swirls, which resemble cream being stirred into coffee, range in size from a few metres across to more than 50 kilometres, and they have been spotted all over the surface of the moon. But their nature 鈥� and how exactly they form 鈥� has remained enigmatic for decades.
at the Planetary Science Institute in Tucson, Arizona, and her colleagues used data from NASA鈥檚 Lunar Reconnaissance Orbiter to build a model of the elevation around two swirls, located in an area called Mare Ingenii. The maps showed that the bright areas of the swirls were, on average, 2 to 4 metres lower than the darker areas within and around the swirls.
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鈥淚t鈥檚 been looked at before, but never with this level of spatial resolution, and at larger spatial scales this correlation is not apparent,鈥� says Domingue. 鈥淚t was definitely a surprise.鈥�
Because all lunar swirls seem to be associated with small-scale magnetic fields, previous explanations for them centred on how those fields protected the ground from weathering caused by particles from the sun. 鈥淲e still think that shielding from the solar wind does play an important role in forming lunar swirls, but what our analyses show is they might not play the only role, and other processes must be going on,鈥� says Domingue.
The differences in elevation, combined with other measurements of the grain sizes of the dust in lunar swirls, suggest that these other processes are related to how dust moves across the lunar surface.
Domingue and her colleagues are now working on extending their analyses to lunar swirls in other regions of the moon, as well as figuring out how lunar dust grains of different sizes move. This question is important not just for figuring out how the swirls form, but also for any long-term installations or bases on the moon that want to avoid being filled with fine lunar sand.
Geophysical Research Letters
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