Apollo 11 - Moonquakes

It's 40 years today that Apollo 11 left Earth, and four days later humans first set foot on the Moon. I was a college lad, and I sat with friends around the tv to watch. What a stunning achievement - if only we could muster that same dedication, intelligence, creativity, and funding towards solving some of the critical issues that face us today.

From NASA: "Between 1969 and 1972, Apollo astronauts placed seismometers at their landing sites around the moon [as Buzz Aldrin is doing below]. The Apollo 12, 14, 15, and 16 instruments faithfully radioed data back to Earth until they were switched off in 1977."

"There are at least four different kinds of moonquakes: (1) deep moonquakes about 700 km below the surface, probably caused by tides; (2) vibrations from the impact of meteorites; (3) thermal quakes caused by the expansion of the frigid crust when first illuminated by the morning sun after two weeks of deep-freeze lunar night; and (4) shallow moonquakes only 20 or 30 kilometers below the surface.

"The first three were generally mild and harmless. Shallow moonquakes on the other hand" could yield magnitude 5.5 tremors.

Seismograms from three types of moonquakes recorded at the Apollo 16 station. LPX, LPY, and LPZ are the three long-period components and SPZ is the short-period vertical component. The first column shows a deep-focus moonquake; the center column, a shallow moonquake; the third column shows records of the impact of meteoroid on the lunar surface. [From ETH website; courtesy of NASA].