Apollo S-IVB stages where crashed into the Moon on mission Apollo 13, 14, 15, 16 and 17 in support of geophone measurements. I can't say I know the location of all of them. The Apollo 14 S-IVB site is at S8°10', W26°03' selenographic coordinates. Its impact streak mark appears on Lunar Topographic Orthophotomap (LTO) 76-D1. Such lunar targets are too small to be detected using Earth-based amateur telescopes. Generally, the impacts are discussed in each Apollo mission's preliminary science report. Here's a link to the Apollo 16 report: http://www.hq.nasa.gov/alsj/a16/a16psr.html (65mb) The S-IVB impacts are discussed on page 9-20 and 9-21 of the Apollo 16 report. Also of entertainment reading interest is the "Stalin organ" - an automatic mortar launcher - left on the Moon at the Apollo 16 site - shown on page 10-21 of the Apollo 16 report. The mortar rounds were used to generate siesmic signals in order to probe the structure of the subsurface terrain around the landing site and to calibrate the geophones. Apollo geophones operated for some years, recording thousands of microearthquakes and meteor impacts on the Moon. Most of the moonquakes are from a layer near the Moon's surface. From that data, only a partial, incomplete picture of the Moon's deep interior has been built up. This is mostly because all the geophones are located on the near side of the Moon and all the S-IVB impacts were also on the near side. Although siesmic waves from some of lunar quakes have returned limited data on the structure of the deep interior and core of the Moon, modeling of the Moon's core is subject to varying interpretations because of the limited data. One of the science objectives of the current return to the Moon initiative - with the "land anywhere" capability of the "LEM on steriods" that you saw in last night's presentation, is to complete a siesmic station grid by placing more stations on the backside of the Moon. Ziggy asked about the potential for creating lunar orbiter stations from expended booster parts. There are no fuel-free stable low (<200km) orbits around the Moon. This is because there are sizeable mascon's - massive gravity concentrations - beneath the lunar surface - that disrupt any stable orbits. Because of the stable-orbit fuel requirement, a permanent low lunar orbit station is out-of-the-question. Usually, lunar "orbit" stations are discussed in terms of lunar transfer stations - refueling stations placed at the _lunar_ leading and trailing LaGrange points. The LaGrange points are relatively fuel-free in terms of station keeping requirements. If there is any water at the lunar poles, it could be turned into fuel and then ferried up to automated LaGranage transfer stations for use by that Earth-to-Moon ferry that you remember from 2001: A Space Odyessy. Prior to Apollo, the lunar mascons were relatively unknown. The mascons were indirectly discovered during the Lunar Orbiter missions and as part of correcting large errors in models that drove the Apollo 12 navigation system. Initial navigation models for lunar landings had large errors in them (2 kilomters). After the effect of the mascons were taken into account, Apollo 12 was able to land within 30 meters of the prior Surveyor robot lander. The mascons again reared their heads at the end of the 1972 Apollo 16 mission. A small subsatellite, PFS-2 ("Particles and Fields Subsatellite"), was thrown out the back of the Apollo 16 Command Module with the idea of leaving it in an unpowered low lunar orbit (89 to 122 km). The PFS-2 satellite would remain in orbit and measure charged particles in the very thin - but existant - lunar atmosphere over the next year. Back then, the extent of the lunar mascons were not fully understood. The mascon's gravitational effect perturbed the unpowered PFS-2 orbit. Instead of staying in lunar orbit for a year - the satellite crashed into the lunar surface 35 days after deployment. The PFS experiment is discussed - sans dicussion of the lunar mascons and the experiment's early termination - in Chapter 21 of the Apollo 16 Preliminary Science Report. The effect of the mascons on the early termination of the PFS-2 experiment is discussed in this NASA press article - http://science.nasa.gov/headlines/y2006/06nov_loworbit.htm . The PFS-2 experiment was still a success. The thirty five days of low lunar magnetic readings expanding our understanding of the distribution of the lunar magnetic field. That there are no fuel-free low lunar orbits around the Moon may have changed last year. Some enterprising physicist published a paper claiming to have come up with a theoretical highly elliptical lunar orbit that would be fuel-free and stable. The suggestion was to use it to orbit at series of small communications satellites, e.g. - GPS and cell phone service for the entire Moon. If such a fuel-free orbit does exist and if a chain of lunar GSP and communications relays could be set up, it would revolutionize lunar exploration. It means you could have a network of Mars-type rovers - run in almost real-time - by shirt-sleeved Earth based scientists. Having a lunar GPS system is also a good safety measure for human exploration. If you lunar lander blows a tire, it's nice to know that AAA could use a lunar OnStar to send the tow truck to just the right place. The mascons also present a hurdle for theorists who model the early evolutionary history of the Moon. As we all know from experience, heavy, dense objects sink to the bottom of bathtub; lighter, less dense objects float on top. The relatively near surface mascons present a counter-intuitive dilemma for modeling the Moon's early formation. If the early Moon was a totally molten liquid, it should have separated into layers by density like some popular drinks you can buy in any local bar. How do you model an early Moon that gets the mascon concentrations - which consist of relatively heavy materials near the surface of the Moon, floating on top of layers of the relatively lighter, less dense materials that are closer to the Moon's core? Enjoy the eclipse. - Kurt ____________________________________________________________________________________ Looking for last minute shopping deals? Find them fast with Yahoo! Search. http://tools.search.yahoo.com/newsearch/category.php?category=shopping