NASA's Lunar Reconnaissance Orbiter has captured the sharpest images ever taken from space of the Apollo 12, 14 and 17 landing sites on the moon.

The pictures, which the space agency released on Tuesday, show the tacks and debris left by astronauts and their lunar rovers on the Moon's surface in the 1960s and 1970s.

LRO has recently lowered its orbit from 50 km above the Moon's surface to just 25 km. In the photos of the Apollo 17 site, the tracks made by the lunar rover can be clearly seen with the last foot trails left on the moon.

The cameras, which are overseen by an Arizona State University professor, have captured the sharpest images ever taken from the orbit of the three Apollo landing sites.

NASA scientists say the photos clearly show tracks made by lunar rovers and equipment left behind from the famous Apollo missions of the late 1960s and early 1970s.

We all like to obsess and look at the Apollo landing site images because it's fun, said Mark Robinson, the LROC principal investigator from Arizona State University.

Images taken of the Apollo 17 site, the last manned mission to the moon in December 1972, also show the astronauts' foot trails.

The cameras are attached to the Lunar Reconnaissance Orbiter, an unmanned spacecraft that has been circling the Moon for more than two years. Its goal is to map the moon's surface, record temperatures and measure radiation.

The LRO has been taking pictures of the moon's surface for more than two years. But scientists made an adjustment to its orbit in August that helped produce the higher resolution images.

The maneuver temporarily lowered the LRO from its usual orbiting altitude of approximately 31 miles from the moon's surface to as low as 13 miles.

The spacecraft remained in the lower orbit for four weeks, long enough for the moon to completely rotate and for the LRO wide angle camera to get the pictures of the three landing sites and the trails astronauts left in the moon's thin soil as they stepped out of the relative safety of their lunar modules and explored the moon on foot.

LRO has been a highly productive mission. It has now returned several hundred thousand pictures of the lunar surface.

Erosion processes on the moon work much slower than on an active planet like the Earth. Eventually, though, all traces of the moon landings will be erased.

The lunar body is constantly bombarded by micrometeorites that will, in time, mix up the boottracks and break down the equipment. It has been estimated that rock at the surface erodes at a rate of about 1 mm per million years.