Probe pictures Moon landing sites
Remarkable new images of the Apollo landing sites on the Moon have been released by Nasa.
The pictures clearly show the hardware left on the lunar surface by American astronauts in the 1960s and 70s, including Apollo 17's "Moon buggy".
The images were acquired by the robotic Lunar Reconnaissance Orbiter (LRO), which has been circling Earth's satellite since 2009.
Such shots have been returned before, but these are the best yet.
LRO has recently lowered its orbit from 50km above the Moon's surface to just 25km.
This makes it easier to see equipment, such as the descent stages that put the astronauts on the surface. Some of the science experiments are visible, also - as are the trails of bootmarks left in the dirt as the crews positioned these science packages.
The Apollo 17, 14 and 12 sites are the focus of the latest release.
They were viewed by the narrow-angle imaging system on LRO's Lunar Reconnaissance Orbiter Camera (LROC) instrument.
At the lower altitude, this instrument sees objects at a resolution of 25cm by 25cm per pixel.
In an extreme blow-up of the Apollo 17 Lunar Roving Vehicle (LRV), it is just possible to discern the condition in which the astronauts Eugene Cernan and Harrison Schmitt parked the buggy - with its wheels turned to the left.
LRO has been a highly productive mission. It has now returned several hundred thousands pictures of the lunar surface.
The probe was originally conceived as a robotic precursor to future manned missions. However, when Nasa might return to the lunar body with astronauts is not clear. Last year, US politicians cancelled the project, known as Constellation, that was intended to achieve this feat.
"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, Tempe.
"People actually used to be able to go to the Moon; people used to explore the Moon - and hopefully sometime in the future that will continue again. But LROC is looking at the whole Moon and we've taken about 1,500 of these high-resolution images distributed all around the Moon… and this is just a huge resource for anybody studying the Moon, doing science; and engineers planning to go back to the Moon in general and to specific sites."
Erosion processes on the Moon work much slower than on an active planet like 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 1mm per million years.
"In human years, it may seem like forever, but in geologic terms probably there will be no traces of the Apollo exploration in let's say 10 to 100 million years," said Dr Robinson.
On Thursday, Nasa will launch its latest Moon mission - the Gravity Recovery and Interior Laboratory (Grail).
This is a pair of satellites that will survey the Moon's gravity in unprecedented detail. The data will reveal its internal structure, helping to explain how the lunar body formed and why its nearside now looks so different from its farside.