Forum Replies Created
-
Posts
-
Hello Bill
Thank you for your answer.
I guess the lava flooding in Imbrium would have been a great sight, seen ”live” in a telescope from the Earth.
Lars
This is a fine book. I have read it this weekend and enjoyed it.
I will not make a review here, but will mention one thing that puzzles me. The lava flows.
The book explains the geologic periods with the heavy bombardment, creation of the maria, the Imbrium basin, new craters inside the Imbrium and shows that the lava flows came last.
On page 97 an illustration shows the Moon with all maria and Imbrum etc. before and after the lava flows ”filling pre-existing impact basins”.
It will take a rather large amount of lava to fill the Imbrium basin up an almost bury craters like Archimedes (page 76 and 79)– not to mention all the other places to be filled up on the Moon (at the same time).
Where did all that lava come from? I reckon that this flowing has taken some time – the early and late Imbrian periods where the lava flowed lasted from 3.84 – 3.2 billion years ago (p.107), that is 600 million years give or take a million or two.
The author writes on p. 97: “The lunar maria were formed when molten magma generated by the heat of radioactive decay and the subsequent melting of rock in the Moon’s mantle erupted to the lunar surface over 3 billion years ago, filling the floors of impact basins that had themselves been created some hundred of million years before that.”
But the Moon had a solid crust – the crust solidified in the pre-nectarian period, it is said on p. 106 – I would think that the Moon was cooled so there was not that much heat left.
I mean, first you must have enough molten lava to fill the entire surface of the Moon and then you have to keep it warm and liquid for up to 500 million years.
Unless of course the flow-period was much shorter.
How long would it take to fill the Imbrium?
Having the recent eruptions on Hawaii in mind, where the lava comes out of every fissure and runs across the island, one might think that the Imbrium job was a matter of months, but to fill the Imbrium basin with a layer of lava more than 2-3 km (?) thick is something else.
Did the lava fill Imbrium like water rising in a bowl, or did the first layer solidify so the next flow had to come up through the first etc.? And how thick is the layer of lava?
Charles A. Wood writes in “The modern Moon” (p. 42) that there were three lava flows in Imbrum and the second “extend 600 km…is only 35 meters thick and has washed down a almost nonexistent slope of 0.01˚. The lava must have been very fluid, more like water and it must have roared across the Moon’s surface at speeds of many kilometers pr. hour.”
35 meter is not much, and the layer of lava around Montes Pico and Piton and the other “costal areas” around Imbrium must have been much thicker – several kilometres, I guess. Archimedes is 2 km. high now and must have been much higher (and deeper) before the lava came.
Why would all this lava suddenly break through and flood the surface? Was there a special reason?
My old roll-off observatory is a bit worn and it might be time to replace it with something else. A Pulsar dome seems to be a possibility – although rather expensive – but I fear that moisture might be a problem, as I can read that some of you have to deal with moisture in your domes.
I don’t want to place my telescope inside a wet “tin can”.
Pulsar has made this gadget
https://www.bresser.de/en/Astronomy/Domes/PULSAR-Ventilation-System-for-Observatorium.html
Do you think that this could help?
Regards
LarsIt looks very fine. But it seems that the house is blocking a part of your horizon. Which way is south?
Lars
>A bit like solar eclipses, after your first success, you will be hooked for life!
That’s right. I had my last succesful occultation-observation i 1986…
I have watched almost thousand predicted events since then, but no luck.
As they say: you have to kiss an awful lot of frogs to find a prince
Regards
Lars>Lars (Denmark) you were about 2 path widths North of the predicted track.
Yes, 67 km north according to the prediction. I observed from 23.43 – 23.50 UT and nothing happened. About 23.50 clouds came in and covered the sky.
It is reported that Mayak failed to deploy the light-reflecting surface
The satellite should pass here in Denmark at 1:45 Danish summer time (GMT+2) but it was not visible. Maybe the sail did not deploy as planned.
I saw this occultation from my home in Denmark with a friend, and we had to move the telescope around in the garden to find at spot where we could see Saturn. The planet was very low and just over the roof of the next bulding which emitted a lot of heat and made turbulence.
We timed the occultation with my wrist watch and it began about 0h 40m and ended 0h 45m on the 4th of July Danish summer time. (GMT +2)
We did not report it to anyone, but we had a great time.
I suppose Guide is using the same data as your ephemeris. The Guide position at 27. March 0.00 is off by 10 minutes in RA and 55′ in Dec. compared to your figures. No problem if the comet was mag 9 (and the ephemeris was valid).
