text:  The rotational axis of the Moon lies within Shackleton , only a few kilometers from its center . The crater is 21 km in diameter and 4 @.@ 2 km deep . From the Earth , it is viewed edge @-@ on in a region of rough , cratered terrain . It is located within the South Pole @-@ Aitken basin on a massif . The rim is slightly raised about the surrounding surface and it has an outer rampart that has been only lightly impacted . No significant craters intersect the rim , and it is sloped about 1 @.@ 5 ° toward the direction 50 – 90 ° from the Earth . The age of the crater is about 3 @.@ 6 billion years and it has been in the proximity of the south lunar pole for at least the last two billion years . 
  