Astronomy Picture of the Day [1]Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. 2019 July 21 [2]See Explanation. Clicking on the picture will download the highest resolution version available. Moonquakes Surprisingly Common Image Credit: [3]NASA, [4]Apollo 11 Crew Explanation: Why are there so many moonquakes? Analyses of [5]seismometers left on the moon by the [6]Apollo moon landings reveals a surprising number of [7]moonquakes occurring within 100 kilometers of the surface. In fact, 62 [8]moonquakes were detected in data recorded between 1972 and 1977. [9]Many of these moonquakes are not only strong enough to [10]move furniture in a [11]lunar apartment, but the stiff rock of the moon continues to vibrate for many minutes, significantly longer than the softer rock [12]earthquakes on [13]Earth. The cause of the moonquakes remains unknown, but a [14]leading hypothesis is the collapse of underground faults. Regardless of the source, [15]future moon dwellings need to be built to withstand the frequent shakings. [16]Pictured here 50 years ago today, [17]Apollo 11 astronaut [18]Buzz Aldrin stands beside a recently deployed [19]lunar seismometer, looking back toward the [20]lunar landing module. Tomorrow's picture: moon circle __________________________________________________________________ [21]< | [22]Archive | [23]Submissions | [24]Index | [25]Search | [26]Calendar | [27]RSS | [28]Education | [29]About APOD | [30]Discuss | [31]> __________________________________________________________________ Authors & editors: [32]Robert Nemiroff ([33]MTU) & [34]Jerry Bonnell ([35]UMCP) NASA Official: Phillip Newman [36]Specific rights apply. [37]NASA Web Privacy Policy and Important Notices A service of: [38]ASD at [39]NASA / [40]GSFC & [41]Michigan Tech. U. References 1. https://apod.nasa.gov/apod/archivepix.html 2. https://apod.nasa.gov/apod/image/1907/AldrinSeismometer_Apollo11_3000.jpg 3. https://www.nasa.gov/ 4. https://www.hq.nasa.gov/office/pao/History/alsj/a11/a11.crew.html 5. https://en.wikipedia.org/wiki/Seismometer 6. https://nssdc.gsfc.nasa.gov/planetary/lunar/apolloland.html 7. https://en.wikipedia.org/wiki/Quake_(natural_phenomenon)#Moonquake 8. http://adsabs.harvard.edu/abs/2017PEPI..262...28G 9. https://science.nasa.gov/science-news/science-at-nasa/2006/15mar_moonquakes 10. https://www.youtube.com/watch?v=A75icqf9M6w 11. http://spaceflight.nasa.gov/gallery/images/vision/lunar/ndxpage1.html 12. https://earthquake.usgs.gov/learn/facts.php 13. http://antwrp.gsfc.nasa.gov/apod/image/0208/earthlights02_dmsp_big.jpg 14. http://adsabs.harvard.edu/abs/2017PEPI..262...28G 15. https://apod.nasa.gov/apod/ap171025.html 16. https://www.flickr.com/photos/nasacommons/9457418581/in/album-72157634973926806/ 17. https://www.lpi.usra.edu/lunar/missions/apollo/apollo_11/experiments/ 18. http://en.wikipedia.org/wiki/Buzz_Aldrin 19. https://www.lpi.usra.edu/lunar/missions/apollo/apollo_11/experiments/pse/ 20. https://apod.nasa.gov/apod/ap030920.html 21. https://apod.nasa.gov/apod/ap190720.html 22. https://apod.nasa.gov/apod/archivepix.html 23. https://apod.nasa.gov/apod/lib/apsubmit2015.html 24. https://apod.nasa.gov/apod/lib/aptree.html 25. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search 26. https://apod.nasa.gov/apod/calendar/allyears.html 27. https://apod.nasa.gov/apod.rss 28. https://apod.nasa.gov/apod/lib/edlinks.html 29. https://apod.nasa.gov/apod/lib/about_apod.html 30. http://asterisk.apod.com/discuss_apod.php?date=190721 31. https://apod.nasa.gov/apod/ap190722.html 32. http://www.phy.mtu.edu/faculty/Nemiroff.html 33. http://www.phy.mtu.edu/ 34. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html 35. http://www.astro.umd.edu/ 36. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 37. https://www.nasa.gov/about/highlights/HP_Privacy.html 38. https://astrophysics.gsfc.nasa.gov/ 39. https://www.nasa.gov/ 40. https://www.nasa.gov/centers/goddard/ 41. http://www.mtu.edu/