The Moon and Planets

[Eric Mc]

I think it would be nice to have a thread for discussion of the above. At the moment they tend to get discussed in the context of specific space probe missions or even dumb conspiracy theories.

However, they are interesting bodies in their own right and we could discuss the various probes, landers, rovers etc all in one spot.

For example, this morning the Chinese managed to safely return the first ever rock samples from the moon's far side.

[Eric Mc]

He was a regular on the various BBC Horizon programmes that covered the Voyager missions and other NASA space probes.

I would also like some chat on the moon and planets themselves i.e. what are they like atmosphere and geology wise and how they interact with each other etc.

[Eric Mc]

Even our moon throws up surprises. The discovery of water on the moon just over 20 years ago was not expected at that time - after the original analysis of the Apollo samples indicated that the moon was very dry. It turns out that the Apollo samples did indeed contain evidence of water but it took more modern analytical techniques to find it.

On Radio 4 this morning they said that for the first two years, the samples returned today will be exclusively available to Chinese scientists only but after that some samples will be distributed to other countries' labs.

[Eric Mc]

Simpo Two said:

Could Apollo have landed men on the far side of the moon?

Technically yes but there would have been a number of additional issues that would have needed to be addressed.

The main one was communications. Without some sort of relay satellite, it is impossible to maintain radio contact with an object on the far side of the moon - whether the object is in lunar orbit or on the surface. A relay satellite of some sort is required. It could have been technically done between 1968-1972 but NASA's budget for the lunar landings had never anticipated the need to land on the far side, so no work, as far as I am aware, was ever carried out in designing a relay satellite.

Having said that, Dr Harrison Schmitt, the Lunar Module Pilot on Apollo 17 and the only qualified geologist to walk on the moon, made a real nuisance of himself in the Astronaut's Office by lobbying hard for a landing on the far side. However, he was told to shut up about it or he'd get bumped off Apollo 17 - so he calmed down.

The Chinese now have a relay satellite at one of the moon/earth/sun Lagrange points which allows radio signals from their far side landers and rovers to talk to earth.

[Eric Mc]

WrekinCrew said:

Would there have been some times when the orbiting Command Module could see both the lander and Earth, and acted as a relay?
I guess it depends how far into the far side they landed.

Edited by WrekinCrew on Tuesday 25th June 11:23

The answer is yes - but the window available to act as a relay would be very short. Some of the crucial steps in a near side lunar landing actually happened on the far side, out of communications with earth. For example, it was usual for the Lunar Module (LM) and Command Module (CM) to perform the pre-landing separation manoeuver on the far side. So normally the Command Module would emerge from behind the moon a few minutes earlier than the Lunar Module, which would be on its way down to the surface and at a lower altitude. In those circumstances, the CM could start communicating to Mission Control a bit earlier than the LM and could be used as a relay. But the LM would establish direct contact with earth just a few minutes later.

[Eric Mc]

Not heard of that one. Have you any pictures?

[Eric Mc]

But since they never planned a far side landing , it was never considered,

[Eric Mc]

SpudLink said:

The European Space Agency previously said radar signals indicated there was possibly a large liquid water lake under Mars' ice cap.
Research now indicates it is more likely to be variations in the ice, rather than liquid...
https://www.telegraph.co.uk./science/2024/06/07/ma...

Ineresting - although from a practical point of view (i.e. human exploitation) whether it's frozen or liquid water isn't that big an issue.

[Eric Mc]

The problem is that there are thousands of these Kuiper Belt Objects (KBOs).

[Eric Mc]

I've always liked "Solar System" topics because, even though the solar system is pretty big, it is our own "cosmic back yard" and we have been able to send probes to virtually all the major bodies that exist in the solar system.

[Eric Mc]

Can we try to keep on Solar System topics rather than the universe in general?

What do people think is the most interesting moon in the Solar System?

I am constantly amazed at the variety of the moons we have - from frozen ice worlds to semi molten hot worlds.

[Eric Mc]

Better than nothing😊

[Eric Mc]

SpudLink said:

Our moon is interesting because of it's large size relative to Earth, and the possible influence it has had on the evolution of life. But not that interesting for itself.

Europa has to be the most interesting because of the (very very remote) possibility of the oceans supporting life 'as we know it'. But probably not the most interesting geologically, which I guess is what you have in mind.

Clarke wrote that just after the Voyagers had flown by Jupiter but not visited any other planets yet.
I’d nominate both Titan and Triton as very weird worlds.