¿ 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. 2020 December 7 [2]See Explanation. Clicking on the picture will download the highest resolution version available. Mammatus Clouds over Mount Rushmore Image Credit & Copyright: [3]Laure Mattuzzi Explanation: What's that below those strange clouds? Presidents. If you look closely, you may recognize the heads of [4]four [5]former [6]US [7]Presidents carved into famous [8]Mount Rushmore in [9]South Dakota, [10]USA. More obvious in the [11]featured image are the unusual [12]mammatus clouds that passed briefly overhead. Both were captured together by a [13]surprised tourist with a quick camera in early September. Unlike normal [14]flat-bottomed clouds which form when moist and calm air plateaus rise and cool, bumpy [15]mammatus clouds form as icy and turbulent air pockets sink and heat up. Such turbulent air is frequently accompanied by a thunderstorm. Each [16]mammatus lobe spans about one kilometer. The [17]greater mountain is known to native [18]Lakota Sioux as [19]Six Grandfathers, deities responsible for the directions north, south, east, west, up, and down. Tomorrow's picture: an almost great conjunction __________________________________________________________________ [20]< | [21]Archive | [22]Submissions | [23]Index | [24]Search | [25]Calendar | [26]RSS | [27]Education | [28]About APOD | [29]Discuss | [30]> __________________________________________________________________ Authors & editors: [31]Robert Nemiroff ([32]MTU) & [33]Jerry Bonnell ([34]UMCP) NASA Official: Phillip Newman [35]Specific rights apply. [36]NASA Web Privacy Policy and Important Notices A service of: [37]ASD at [38]NASA / [39]GSFC & [40]Michigan Tech. U. References 1. https://apod.nasa.gov/apod/archivepix.html 2. https://apod.nasa.gov/apod/image/2012/MammatusRushmore_Mattuzzi_3024.jpg 3. https://www.instagram.com/lauremattuzzi/ 4. https://en.wikipedia.org/wiki/George_Washington 5. https://en.wikipedia.org/wiki/Thomas_Jefferson 6. https://en.wikipedia.org/wiki/Theodore_Roosevelt 7. https://en.wikipedia.org/wiki/Abraham_Lincoln 8. https://en.wikipedia.org/wiki/Mount_Rushmore 9. https://en.wikipedia.org/wiki/South_Dakota 10. https://www.cia.gov/library/publications/the-world-factbook/geos/us.html 11. https://www.instagram.com/p/B16kVwVJA1b/ 12. https://scool.larc.nasa.gov/GLOBE/mammatus.html 13. https://images-na.ssl-images-amazon.com/images/I/71MPw6CiXEL._AC_SX425_.jpg 14. https://www.abc.net.au/news/2020-09-01/flat-bottom-clouds-and-the-science-behind-them/12591230 15. https://apod.nasa.gov/apod/ap191215.html 16. https://earthsky.org/earth/amazing-photos-of-mammatus-clouds 17. https://youtu.be/7r1nV8pMJ9g?t=25 18. https://en.wikipedia.org/wiki/Lakota_people 19. https://eos.org/features/mount-rushmores-six-grandfathers-and-four-presidents 20. https://apod.nasa.gov/apod/ap201206.html 21. https://apod.nasa.gov/apod/archivepix.html 22. https://apod.nasa.gov/apod/lib/apsubmit2015.html 23. https://apod.nasa.gov/apod/lib/aptree.html 24. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search 25. https://apod.nasa.gov/apod/calendar/allyears.html 26. https://apod.nasa.gov/apod.rss 27. https://apod.nasa.gov/apod/lib/edlinks.html 28. https://apod.nasa.gov/apod/lib/about_apod.html 29. http://asterisk.apod.com/discuss_apod.php?date=201207 30. https://apod.nasa.gov/apod/ap201208.html 31. http://www.phy.mtu.edu/faculty/Nemiroff.html 32. http://www.phy.mtu.edu/ 33. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html 34. http://www.astro.umd.edu/ 35. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 36. https://www.nasa.gov/about/highlights/HP_Privacy.html 37. https://astrophysics.gsfc.nasa.gov/ 38. https://www.nasa.gov/ 39. https://www.nasa.gov/centers/goddard/ 40. http://www.mtu.edu/