Published online 13 April 2005 | Nature | doi:10.1038/news050411-5

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Moon images reveal bright spots for lunar base

Perpetually sun-drenched sites could become prime real estate.

This chart shows the regions of perpetual illumination at the lunar pole.This chart shows the regions of perpetual illumination at the lunar pole.

A few precious spots on the Moon may be bathed in permanent sunlight, according to planetary scientists. These bright, temperate areas might make ideal sites for a lunar base.

Researchers have long suspected that mountains and crater rims at the Moon's poles might bask in constant sunshine. But without a detailed analysis of the lunar landscape, this has been a tough theory to test.

A team led by Ben Bussey of the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, analysed pictures taken by the spacecraft Clementine, which circled the Moon in 1994. The researchers overlaid a series of images of the Moon's north pole taken over a lunar day - which lasts about 28 Earth days - and searched for regions that are constantly illuminated.

A handful of spots on the rim of the Peary crater were lit for the entire lunar day, Bussey's team reports in Nature1 - and may be sun-baked all year round. A person standing there would see the Sun hover near the horizon but never sink below it. "It would be very surreal and very beautiful," says team member Paul Spudis, also at Johns Hopkins.

The Sun never sets

Nowhere on Earth enjoys all-year sunlight, because the planet's axis is tilted about 23º relative to the plane of its orbit around the Sun. Each of the poles basks in 24-hour sunlight when it is leaning towards the Sun in summer - but it dwells in permanent darkness when tilting away from it in winter.

The Moon, by contrast, sits more upright, being tilted at just 1.5º relative to the Earth's path around the Sun. This led scientists to believe that certain lunar peaks might remain in sunshine all year round.

Bussey's team carried out their analysis of the north pole during the lunar summer, when it was tilted towards the Sun. To see whether the sites remain lit during the lunar winter, they will need snapshots of the pole during that time, or a more accurate map of the area's topography. This should be achieved by one of a series of planned lunar missions such as Chandrayaan-1, which is scheduled for launch in 2007.

Warm and welcoming

The perpetually sunlit spots proposed by Bussey's team could make perfect sites for building a manned lunar base. For one thing, they would benefit from bountiful solar energy.

What's more, climate calculations suggest that they would hover at a relatively balmy -50 ºC. This is far more hospitable for man and machine than the Moon's equatorial regions, in which temperatures swing wildly from -180 ºC to 100 ºC. "It's quite mild in space terms," Spudis says.

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Bussey's analysis is particularly timely because of the Bush administration's goal of sending astronauts back to the Moon and on to Mars. "It gives us a solid idea about one aspect of where missions should go," says lunar scientist Jeff Taylor of the University of Hawaii in Honolulu.

The lunar poles are already enticing because of suggestions that they might hold pockets of ice, and hence a supply of water. Earlier analyses by Bussey's team revealed dips in the polar landscape, such as crater bottoms, that are in permanent shadow and might harbour ice. They also analysed the lunar south pole for permanently sunlit spots - but came up empty-handed. 

  • References

    1. Bussey, D. B. J., Fristad, K. E.,Schenk, P. M., Robinson, M. S. & Spudis, P. D. Nature, 434, 842 (2005). | Article | PubMed | CAS |