permanently shadowed craters – Behind The Black

There likely is little or no ice in the Moon’s permanently shadowed craters

March 13, 2024 11:47 am Robert Zimmerman

The floor of Shackleton Crater showing no obvious ice deposits,
as seen by Shadowcam. The black cross marks the south pole.
Click for original image.

This week the 55th annual Lunar and Planetary Science Conference is being held in Texas. The conference was originally established in connection with the Apollo missions to allow scientists to release their Moon research results. It quickly morphed into an annual event covering research from the entire planetary research community.

I have reviewed the abstracts for this year’s meeting, and culled what I think are the most significant new results from the conference, which I will report on in the next few posts.

We begin however with possibly the most important result from the conference, given by the science team for the ShadowCam instrument on South Korea’s Danuri lunar orbiter. That low-light camera was designed to take high resolution pictures of the permanently-shadowed craters of the Moon, to see if there was any visible or obvious ice hidden there. Though the science team presented a number of papers, the summary paper [pdf] by the instrument’s principal investigator, Mark Robinson of Arizona State University, gave the bottom line:

The data so far is finding very little evidence of water ice in these dark regions.
» Read more

15 comments

Moon’s south pole permanently shadowed regions are younger than expected

September 13, 2023 1:26 pm Robert Zimmerman

Click for original image.

A new long range model of the Moon’s orbit and rotational tilt now suggests that the permanently shadowed regions (PSRs) in its south polar regions are much younger than previous predicted, which reduces the likely amount of ice that has been preserved there.

The map of the south pole region to the right, reduced, sharpened, and annotated to post here, shows the locations of those shadowed regions, with their predicted ages indicated by the colors (Gyr = billion years). Note that the Nova-C lander, planned for launch in mid-November, will land somewhat near some relatively young PSRs, as indicated by the red cross. From the press release:

“We calculated the lunar spin axis orientation and the extent of PSRs based on recent advances for the time evolution of the Earth-Moon distance,” he said. Early in its history, the Moon (which is 4.5 billion years old) was bombarded by comets and volcanism released water vapor from its interior, but continuously shadowed areas started to appear only 3.4 billion years ago. By that time these processes had started to die down, so most of the water that was delivered to the Moon or outgassed from its interior could not have been trapped in the polar regions. Any ice in the polar regions today must have a more recent origin.

“We have been able to quantify how young the lunar PSRs really are,” Schorghofer said. “The average age of PSRs is 1.8 billion years, at most. There are no ancient reservoirs of water ice on the Moon.”

Since other data suggests the presence of ice, it is possible that these reserves are regularly renewed by the arrival of impacts. It also suggests however that there might be less ice available than hoped. Above all, the red colored regions appear to be the most valuable real estate to explore first.

Note: The landing sites for both India’s Vikram lander and Russia’s Luna-25 lander were well beyond the map’s upper right edge, far outside the region where any permanently shadowed craters are located. The news outlets that talked about finding water or ice on either mission were simply illustrating their ignorance and sloppy reporting.

6 comments

Studying the Moon by starlight

January 7, 2012 10:34 am Robert Zimmerman

The Moon's south pole by starlight

In a paper published today in the Journal for Geophysical Research, Planets, the science team for Lunar Reconnaissance Orbiter describe how they have used starlight to peer into the permanently shadowed craters of the Moon’s north and south poles. Looking only during the lunar night, they measured the dim albedo of the Moon from reflected starlight. From this very weak signal they were able to cull two interesting facts about these very cold and very dark places.

The ground at the bottom of these craters is more porous than the surrounding unshadowed terrain.
There is evidence in the spectroscopy of 1 to 2% water frost in these craters.

» Read more