Starship Asterisk*

Shackleton from ShadowCam

Explanation: Shackleton crater lies at the lunar south pole. Peaks along the 21 kilometer diameter are in sunlight, but Shackleton's floor is in dark permanent shadow. Still, this image of the shadowed rim wall and floor of Shackleton crater was captured from NASA's ShadowCam, an instrument on board the Korea Pathfinder Lunar Orbiter (KPLO) launched in August 2022. About 200 times more sensitive than, for example, the Lunar Reconnaissance Orbiter's Narrow Angle Camera, ShadowCam was designed image the permanently shadowed regions of the lunar surface. Avoiding direct sunlight, those regions are expected to be reservoirs of water-ice and other volatiles deposited by ancient cometary impacts and useful to future Moon missions. Of course, the permanently shadowed regions are still illuminated by reflections of sunlight from nearby lunar terrain. In this stunningly detailed ShadowCam image, an arrow marks the track made by a single boulder rolling down Shackleton crater's wall. The image scale is indicated at the bottom of the frame.

<< Previous APOD

This Day in APOD

Next APOD >>

If I hadn't read the explanation I'd say it was a rhyme, narrow deep grooves. The white point would be a rock of 6-7 m in diameter that entered and exited from the previous crater higher up and that now was stopped in that deeper hole.

The explanation leaves me a little confused. The white arrow is pointing to Shackleton's Crater and says that its diameter is 21 kilometers?

Yet the scale at the bottom says 100 meters and anybody can tell that the 100 meters scale looks far huger than the 21 kilometer diameter crater! Why even if you project the bottom scale along the entire bottom of the photograph, the photo width is roughly only a kilometer from left corner to right corner.

I believe t!he arrow points to the south pole crater!

De58te wrote: ↑Fri May 05, 2023 12:44 pm The explanation leaves me a little confused. The white arrow is pointing to Shackleton's Crater and says that its diameter is 21 kilometers?

Yet the scale at the bottom says 100 meters and anybody can tell that the 100 meters scale looks far huger than the 21 kilometer diameter crater! Why even if you project the bottom scale along the entire bottom of the photograph, the photo width is roughly only a kilometer from left corner to right corner.

Read the text, the arrow points to the trail a rolling boulder left. The whole image is a small section of the crater's wall (also in the text)

I'm curious about the two horizontal lines. The lower one looks like a camera artifact, but the upper one looks like an actual mark on the ground and does not extend the full picture width. What's up with that?

Ironwood wrote: ↑Fri May 05, 2023 5:26 pm I'm curious about the two horizontal lines. The lower one looks like a camera artifact, but the upper one looks like an actual mark on the ground and does not extend the full picture width. What's up with that?

I believe the camera sensor is a linear array, and the image is constructed on the other axis by the movement of the orbiter (or a 2D array that is internally scanned so that the line being integrated tracks the ground position). So images tend to be mosaics created over multiple orbits. In which case, the lines are stitching artifacts.

Sa Ji Tario wrote: ↑Fri May 05, 2023 5:29 am If I hadn't read the explanation I'd say it was a rhyme, narrow deep grooves. The white point would be a rock of 6-7 m in diameter that entered and exited from the previous crater higher up and that now was stopped in that deeper hole.

do you mean this white point?
Like a ball that settled in a hole?
...

I wonder if it is a snow ball