The Moon becomes more dangerous

Yet another risk identified for astronauts living on the Moon. Not only do high speed particles from solar flares and cosmic rays pose a threat, but the Sun spurts out x rays too, which are sometimes energetic enough to kill an unprotected person. New Scientist explains:

It had been thought that the X-rays were not copious enough to be a major hazard, but a new study suggests X-rays really do pose a threat to astronauts working outside of protective spacecraft or bases. The research was carried out by David Smith at the Lunar and Planetary Laboratory in Tucson, Arizona, US, and John Scalo of the University of Texas in Austin, US.

Using the observed rate of solar X-ray outbursts of different magnitudes, they worked out that a lunar astronaut has a 10% chance of receiving a dangerous dose of X-rays from a solar flare for every 100 hours of activity outside of shelters.

The level of radiation they consider harmful is 0.1 Gray or more, which can cause bleeding ulcers and other internal damage, and would certainly increase an astronaut's risk of cancer. The Sun has even produced flares that could kill an unprotected spacesuited human on the Moon, they say, although these are extremely rare.

Astronauts working far outside need to have an x-ray umbrella with them for protection from such outbursts.

It's sad that Robert Heinlein's stories of boy scouts camping on the Moon are not likely to ever come true. (Exploring deep lava tube caves might still be an alternative, though.)