Locating the former Soviet Union’s Luna 9 would be a major historical find. It was the first spacecraft to achieve a lunar soft landing and to transmit photographic data to Earth. After landing in the Ocean of Storms on February 3, 1966, the four petals, which formed the spacecraft, opened outward and stabilized the spacecraft on the lunar surface. Image: NASA/GSFC/NSSDC
The moon is the final resting ground for scads of landed and crashed spacecraft, many of which have been pinpointed recently by sleuthing scientists.
Using observations by NASA's sharp-eyed Lunar Reconnaissance Orbiter, for example, researchers have located and imaged Apollo moon landing leftovers, old Soviet-era spacecraft and, more recently, the impact locales of NASA's twin Grail spacecraft that were deliberately driven into a mountain near the moon's north pole.
But the search is ongoing to find the exact location of several pioneering moon landers.
No luck so far
"We are still looking for [the Soviet Union's] Luna 9 and 13," said Jeff Plescia, a space scientist at the The Johns Hopkins University's Applied Physics Laboratory in Laurel, Md.
"Those were the small 'beach ball' shaped spacecraft," Plescia told SPACE.com "The beach ball might be hard to find, but it made a descent on a larger vehicle which then popped the beach ball off."
Plescia said he had assumed that it would be possible to find the landing sites of Luna 9 and 13 by spotting albedo marks — a change in the lunar surface brightness made by their descent engines.
Plescia is joined in the hunt by Mark Robinson of Arizona State University, principal investigator for the Lunar Reconnaissance Orbiter Camera, or LROC.
"We've both looked, but no luck so far." Plescia said.
Yet another search involves the impact sites of Apollo lunar module ascent stages, hardware discarded once moonwalking crews were snug within their respective command modules. Ascent stages were intentionally impacted into the surface as part of the Apollo Passive Seismic Experiment that studied the propagation of seismic waves through the moon to yield a detailed look at the body's internal structure.
"Given that we have found the impact sites from Grail, you would think we could find those craters, but, again, no luck so far," Plescia said. These, like the craters made by the third stage of NASA's Saturn V moon rocket, "are important to locate to understand how large a crater was made and to have precise coordinates so that the old Apollo era crustal velocity measurements can be reanalyzed."
Scientists hope to find several other lost lunar spacecraft, including NASA's Surveyor 4. Controllers lost contact with this unmanned probe during its descent to the moon on July 14, 1967.
"There are two options," Plescia said. "It completely failed and then just crashed, which would have formed a crater, or it just lost communications and continued to operate and landed. In the latter case, the spacecraft would be on the surface in one piece. The two potential sites have different locations. I made some preliminary searches a while ago, but need to finish it up."
Also on Plescia's to-do list is searching for Luna 18, a 1971 Soviet sample-return mission that failed. Again, communications were lost; it may have landed safely or crashed.
Craters from various fallen orbiters are possible targets as well. The holes gouged out by older missions may prove impossible to find. But coordinates exist for probes such as Europe's SMART 1 and Japan's Kaguya, but no serious search has been mounted yet, Plescia said.
"For Grail it was easy, because we had before and after images, so it was easy to spot the change," he said.