Between July 1969 and December 1972, six teams of United States astronauts ventured across the gap between Earth and Moon to land and walk on that distant world.  Have you ever visited their landing sites?  If not, let's do so now.

We begin with Apollo 11, "Tranquility Base."  The dark gray outline of Mare Tranquilitatis (the Sea of Tranquility) looks almost perfectly round from our earthly vantage point.  The best time to view Mare Tranquilitatis is during the waxing crescent phases, about 5.5 to 6 days after New Moon.  This month, that will be (at least here in North America) on the evening of June 9.  Apollo 11 touched down near the southwestern shore, east-southeast of the craters Ritter and Sabine, fifty years ago next month, on July 20, 1969.  "The Eagle [nickname of the mission's Lunar Module] has landed!"

Of course, the primary mission objective of Apollo 11 is obvious; in the words of the late President John F. Kennedy: to "land a man on the Moon and return him safely to the Earth." But there were also science goals, as well. Clearly, the first goal was to collect samples of the lunar surface. Astronauts Neil Armstrong and Edwin Aldrin collected 49 pounds (22 kg) of rock and soil samples during their single 2.5-hour moonwalk, or EVA (Extra-Vehicular Activity), as well as deployed Apollo Lunar Surface Experiments Package (ALSEP) instruments to check the composition of the solar wind, measure seismic activity, and determine the exact distance to the Moon.  The latter, called the Laser Ranging Retroreflector, is still in use today, as are similar packages left by Apollos 14 and 15. During the exploration, the astronauts also extensively photographed the lunar terrain.

Apollo 12 landed on Oceanus Procellarum (the Ocean of Storms) in November 1969.  Dominating the waxing gibbous phases, the Ocean of Storms covers more than one million square miles of lunar terrain.  The mission's exact landing site lies southeast of the crater Lansberg, which in turn is south-southwest of the prominent crater Copernicus.  The area sees sunrise two nights after First Quarter.  This month, that's on June 12.  Watch as sunlight first bathes Copernicus' sharply defined walls, catching the strong central mountain peak before sliding down to the crater floor.  Mark your calendar to come back in a few nights when the brilliant ray system of Copernicus explodes into view against the darker background of the mare.  Its starburst pattern is unmistakable through even the most modest binoculars.

While Apollo 11's touchdown point was about four miles downrange from the predicted site, Apollo 12's landing crew, Pete Conrad and Alan Bean, really hit the mark.  They landed the Lunar Module, "Intrepid," just 53 feet away from the Surveyor 3 unmanned spacecraft that the United States sent 2.5 years earlier. Beyond collecting more lunar samples, one key mission objective was to bring back components of that spacecraft.  This enabled engineers and materials scientists to study the effect that the harsh lunar environment had on those parts.  Incidentally, there's a long-lived urban legend that researchers examining Surveyor 3's camera, which was one component returned for study, discovered evidence of microorganisms inside the camera that had apparently stowed away before the 1966 launch. Even though that "fake news" persists on-line, it turns out that the microorganisms, Streptococcus Mitis, contaminated the camera after its return to Earth by Apollo 12, as this archived study reports. (Click on the "++ -- Description Continues" to read a capsule summary, where it states "may be the result of accidental contamination of the material after it was returned to Earth.")

After the nearly catastrophic mission of Apollo 13 in April 1970, we returned to the Moon 10 months later with the mission of Apollo 14. Its landing site was the hilly region known as Fra Mauro.  Fra Mauro is found near the southeastern shore of the Ocean of Storms, to the east of Apollo 12.  Fra Mauro experiences sunrise a night earlier, on June 11.

That location was chosen because it is believed to have been formed from debris left over from the impact that formed Mare Imbrium. The samples returned by Apollo 14 showed that Mare Imbrium is no more than about 4.25 billion years old.

Apollo 14 featured the return to space by America's first astronaut, Alan B. Shepard Jr.  Shephard had piloted the first Mercury mission, a suborbital flight known as Freedom 7, almost exactly a decade earlier. Serving as Apollo 14 commander, Shepard and Lunar Module pilot Edgar Mitchell, landed on February 5, 1971. While on the surface, Shepard famously hit a golf ball using a makeshift club made from a Wilson Staff 6-iron head attached to the “contingency return sample collector” he was to use on the Moon.

July 30, 1971 saw Apollo 15 astronauts David Scott and James Irwin touch down next to Hadley Rille and the Apennine Mountains.  The lunar Apennines mark the southeastern edge of Mare Imbrium (the Sea of Rains), just south of the prominent triangle of craters formed by Aristillus, Autolycus, and Archimedes.  All three craters lie near the Moon's terminator, or sunrise line, on the night after First Quarter. Take a look on June 10, or a night or two later if it's cloudy.

Apollo 15 used a second-generation Lunar Module to bring along the first Lunar Rover. During their three EVAs, Scott and Irwin drove the Rover a total of 17.5 miles.  In the process, they gathered over 170 pounds of lunar samples, including a core sample from about 10 feet beneath the lunar surface, and set up their mission's ALSEP instruments. One of the rocks returned became known as the Genesis Rock, one of the oldest samples returned at an estimated age of 4.1 billion years.

Piloted by Commander John Young and Lunar Module Pilot Charles Duke, Apollo 16 landed just north of the crater Descartes in the highlands south of Mare Tranquilitatis on April 20, 1972.  The craters Theophilus and Cyrillus are to the east of the landing site, while Albategnius is roughly an equal distance to its west.  June 9, the night before First Quarter is perfect for viewing this area.  Just west of Albategnius, three more striking craters that almost touch each other's borders – Ptolemaeus, Alphonsus, and Arzachel – see sunrise the following evening.

Apollo 16's landing site in the lunar highlands was chosen so that the astronauts could gather geologically older lunar material than in the lunar maria landing sites of Apollos 11, 12, and 15. Young and Duke drove the second Lunar Rover 16.6 miles (26.7 km) during their three EVAs. Along the way, they gathered 211 pounds (95.8 kg) of lunar samples for return to Earth.  Those samples proved that the area was not volcanic in origin, as had been previously believed.

Apollo 17's landing on December 1972 signaled an end to the Apollo era.  We find its site near the Taurus Mountains, which form the eastern rim of Mare Serenitatis (the Sea of Serenity).  The best time to view this area is during the waxing crescent phases on June 7 and for a few nights thereafter.  The mission's Taurus-Littrow landing site was selected because it offered the best of both worlds, a combination of mountainous highlands and valley lowlands.

Mission Commander Eugene Cernan and Harrison Schmitt explored the region with the third Lunar Rover, covering 22.3 miles (35.9 km) in three EVAs. In the process, they gathered a record 243.7 pounds (110.5 kg) of samples. Schmitt knew especially what to look for, as he was the only trained geologist ever to walk on the lunar surface.

Cernan became the last man to walk on the Moon when he left its surface on December 14, 1972. Before climbing the ladder back into the Lunar Module, his last words from the surface were "…as I take man's last step from the surface, back home for some time to come - but we believe not too long into the future - I'd like to just [say] what I believe history will record. That America's challenge of today has forged man's destiny of tomorrow. And, as we leave the Moon at Taurus-Littrow, we leave as we came and, God willing, as we shall return, with peace and hope for all mankind. Godspeed the crew of Apollo 17."

I find it very sad that Eugene Cernan is still the last man on the Moon nearly half a century later.  When will we return to the Moon?  Who will be the next visitor on the surface to walk in the shadows of our Apollo heroes?  Only time will tell.  But even as we remain confined to our planet for the foreseeable future, we can relive the magic of the historic Apollo program this month as we get ready to commemorate the half-century anniversary of Apollo 11 in July.  Visit each of the landing sites from your own yard this month. And then get ready, because next month, we return to explore in greater detail the Apollo 11 landing site and three commemoratively named craters that lie nearby.

Until next month, remember that half of the fun is the thrill of the chase.  Game on!