Eclipse reveals source of 'moon curse'

Researchers have made a new breakthrough in understanding the source behind 'moon curse.'

Tom Murphy, a physicist at UC San Diego, is among the scientists who have aimed laser beams at suitcase-sized reflectors placed on the moon by Apollo astronauts and unmanned Soviet rovers.

By precisely timing the light's return to Earth, Murphy can measure the distance from here to the moon with millimeter precision.

Lunar ranging, as this is called, has revealed that the moon is slowly spiraling away from us and suggested that it has a molten core.

Murphy's group is using precise measurements of the changing shape of the lunar orbit to subject Einstein's theory of general relativity to the most stringent test yet.

Over time, signals returned by the reflectors, faint to begin with, have faded. The project Murphy leads at Apache Point Observatory in New Mexico sends laser pulses of 100 quadrillion photons, of which, on average, a single lonely photon returns - if any at all. Earth's atmosphere nudges some photons off target so that they hit the lunar soil, and the reflectors slightly diffract the returning beam so that most miss the telescope when they return.

Even after accounting for these losses, Murphy's team records ten times fewer photons than they expect. And on full moon nights it's even worse, dropping to just 1 percent of the predicted performance. Other observatories are unable to detect any returned signal on full moon nights.

Murphy thinks accumulated moon dust could account for the diminished returns, which could spell bad news for plans to place telescopes up there. Although there's no wind on the moon, electrostatic forces and a constant bombardment by tiny meteorites could have kicked up some of the lunar dust to coat the surface of the clear glass prisms arrayed in each reflector.

The findings have been published in the scientific journal Icarus.