Lunar Polar Ice Not Present

pclark999 writes "The New Scientist reports that radar probes of the lunar polar region has disproved earlier theories regarding large sheets of polar ice in craters permanently in the shade. "

Comments

No such thing as permanent shade

[Alan Hicks]

large sheets of polar ice in craters permanently in the shade.

This is a common misunderstanding of the moon. No place on the moon is ever permanently in the shade (excepting something like a cave of course). This comes from the mishandled use of the phrase "dark side of the moon". The moon i tidally locked with earth, meaning that its rotation is such that as it revolves around earth, we always see the same face of the moon. The far face that we do not see is termed "the dark side of the moon". This dark side is actually not always dark. At times when the moon moves between the earth and the sun (the new moon phase) this far side is brightly lit by the sun's light.

Re:No such thing as permanent shade

[Anonymous Coward]

This isn't talking about the dark side of the moon; this is talking about craters on the moon's poles. Just like we have nightless periods (and sunless periods) on our poles, so does the moon. If there is a deep enough crater on the moon at the poles, there might be permanent shadows.

Re:No such thing as permanent shade

[HarveyBirdman]

This is a common misunderstanding of the moon. No place on the moon is ever permanently in the shade (excepting something like a cave of course). This comes from the mishandled use of the phrase "dark side of the moon".

This is a common misunderstanding of what is meant by permanent shading on the moon. Note the phrase "polar ice" is key here.

In the polar regions, the sun is very low in the sky and there are places in deep craters where the sunlight, at any point in the Lunar day, never reaches.

It's the same as on the Earth. The bottom of a deep canyon near the south pole would never receive direct sunlight. The sun never moves above a certain altitude in the sky. Heck, the tilt of the Earth's axis give the poles permanent night (well, twilight) for six months. Not sure what the Moon's tilt is offhand, but that's a side issue.

Re:No such thing as permanent shade

[TopShelf]

You missed the "craters" part. They were working with deep craters, the bottoms of which don't get light due to the steep walls. As you get closer to the pole, the sun sits lower and lower in the southern sky, even when it's "high" noon.

Re:No such thing as permanent shade

[jap]

No place on the moon is ever permanently in the shade

Unfortunately for you, there is such a place. Maybe even more of them, dunno, I left my lunar map in my spacecraft, and I'm not in the mood to fetch it.

The place is called the Shackleton crater - which is a crater at the Lunar South Pole. Because of it location, the bottom of that crater is expected not to be exposed to sunlight ever.

As a coincidence, this is exactly the place where the Clementine mission observed radiation patterns indicating hydrogen presence - and which the referenced article also discusses.

Re:Time for plan B

[HarveyBirdman]

Also Earth is pretty much a sealed ecosystem

Say WHAT?

(although we get tonnes of stuff from space every day)...

Yeah, like, uh, sunlight?

You know... that bright stuff without which 99.9% of this ecosystem could not exist?

Not necessarily...

[Zocalo]

The BBC News site has been carrying a summary of a Nature article on this since yesterday. The telling quote is "The observations, from the Arecibo radio telescope in Puerto Rico, do not rule out ice". The conclusion seems to have been that the ice might still be present, but rather than being thick sheets can only be in small grains or thin sheets. There is also the possiblity of sub-surface ice since the probes can only reach to a depth of several meters into the surface dust.

Roll on the ESA's Smart 1 probe next year which will hopefully resolve the issue.

Re:Disproved??

[Bendebecker]

A theory is an explanation of a particular phenonmen often based on supporting evidence. A hypothesis is a conclusion derived from an understanding of the theory that is often the focus of the experiment. The hypothesis is tested, and depending on its results, a theory is either disporving or it is supported by the hypothesis. It is nearly impossible to prove a theory.

Re:Well, more accurately

[phayes]

Nobody seriously believed that there would be sheets of ice at the lunar poles anyway. When Clementine confirmed the presence of hydrogen at the lunar poles the most commonly accepted source was as hydrates in the lunar regolith.

There are only sources for the hydrogen according to recent theory:
- Cometary impacts
- Cold trapping of the solar wind (this paper details just this scenario: http://fti.neep.wisc.edu/FTI/POSTERS/hhs_space2000 .pdf)

Cometary impacts were always a looong shot.

A side note to those who have been saying "Hydrogen is light, we'll just transport some from the earth to the moon".
- Hydrogen is only RELATIVELY light compared to Earths atmosphere.
- Tanks that can contain large amounts of hydrogen at 0atm are HEAVY.
- We need TONS of hydrogen in order to expand our presence in space.
- Every Kilo of Hydrogen+Tankage that you bring with you from Earth is a kilo that cannot be used for other essentials that we cannot find/make in space. Thinks like food, tools, fuel, etc.
- The two major uses of lunar hydrogen would be water (for drinking, bathing, cleaning, etc) & as rocket fuel.

Pat