Starship Asterisk*

Evolution of the Moon

Explanation: What is the history of the Moon? The Moon was likely created from debris expelled when a Mars-sized object violently impacted the Earth about 4.5 billion years ago. Just after gravitationally condensing, as imagined above, the glowing-hot surface of the Moon cooled and cracked. Rocks large and small continued to impact the surface, including a particularly large impact that created Aitken Basin about 4.3 billion years ago. A Heavy Bombardment period then continued for hundreds of millions of years, creating large basins all over the lunar surface. Over the next few billion years lava flowed into Earth-side basins, eventually cooling into the dark maria we see today. As always, relentless impacts continued, forming the craters we see today, slowly diminishing over the past billion years. Today the cooled Moon we know and love is as dark as coal and always keeps the same face toward Earth. Exactly how the Moon formed initially, and why lunar maria are only on the Earth side, remain active topics of research.

<< Previous APOD

Discuss Any APOD

Next APOD >>

[/b]

Hmm... kinda looks to me like the moon got hit in the face with a Big pizza pie

Be sure to click on the "Moon formed" link, in the last sentence, to a video of William Hartmann's theory.

My question, up for anyone who wants it: many planets have moons... and, while I'm not well-read on the subject, my impression has been that this theory (huge planet-sized impact ejecting and fragmenting off material to form the moon) has only been advocated for earth's moon. Do we have a reason to think that we have a "special case" scenario here? Or is this thought to be a general process for most moons?

I am sure that this theory has been extensively studied, and that PhD's have done the math and proven (if that word can even apply, as there are likely unknown variables) at least its plausibility, but on an elementary level it at least appears this impact theory would have destroyed the planet... also, attributing the earth's spin to this seems a bit of an unnecessary attribute, as many other things in our solar system have associated spins, without necessarily the impact theory to go with it.

So... opinions?

YOU WOULD NOT BE ABLE TO HEAR THOSE IMPACTS from that vantage point. What's more, if you could hear them, you would not hear them simultaneously with the sight of the impacts, but much later. That vantage point must be hundreds of miles from the surface of the moon.

This is one of my pet peeves about science fiction movies. Every time I watch one of those movies, I want to SCREAM at the silver screen, "YOU IDIOTS! YOU CAN'T HEAR SOUNDS IN OUTER SPACE!"

WHY can't they do this right?

And the people who made this short video particularly should know better.

Ron

Jeebo wrote:This is one of my pet peeves about science fiction movies. Every time I watch one of those movies, I want to SCREAM at the silver screen, "YOU IDIOTS! YOU CAN'T HEAR SOUNDS IN OUTER SPACE!"

WHY can't they do this right?

And, even more importantly, the impact sound effects scared my cat as I was watching this.

Sandstone wrote: And, even more importantly, the impact sound effects scared my cat as I was watching this.

One of my cats was totally fascinated by the video!

The other one... oh, wait... maybe I forgot to let him back in for the night...

Jeebo wrote:This is one of my pet peeves about science fiction movies. Every time I watch one of those movies, I want to SCREAM at the silver screen, "YOU IDIOTS! YOU CAN'T HEAR SOUNDS IN OUTER SPACE!"

WHY can't they do this right?

Yeah! And there aren't orchestras out in space either. It would be unsafe working conditions.

I believe the main reason the near side of the moon has many fewer impact craters is that it is tidally locked and the Earth makes a great shield. In order to hit this side of the Moon, an asteroid would have to come at the perfect angle past the Earth but not deviate too much.

In fact the video seems to get this wrong, pelting the near side almost exclusively as if they were all sent from Earth. Also the meteorites seemed to come in two or three discrete bursts, when I think there should be a pretty much uniform activity that became less intense with time. Only if there were credence to the idea of an undiscovered Nemesis planet disturbing the Oort cloud would there be waves of bombardment and that would be linked to the orbital period of such a body, much more often.

If there was more volcanism on this side of the moon, that would have to be related to tidal forces from the Earth, like Io's volcanism.

But why did the volcanism stop if it was happening a billion or so years ago?

If "the Moon we know and love is as dark as coal", then how does it reflect the sun's light so well? I thought it was a sort of greyish colour... Having visited a coalmine I know how (non)reflective coal is...

Presumably, the Earth was subjected to the same "heavy bombardment" as the moon. Is is generally believed that (with some notable exceptions) evidence of this bombardment has been mostly washed away by our oceans, or what?

Jeebo wrote:And the people who made this short video particularly should know better.

actually, the people who chose to post this stupid video on our beloved APOD should know better

i mean, come on, sound in space? PUHLEASE...

I wish they included the Moon's formation, and also Tycho's impact, which may be the biggest recent (108 My) impact.

Actually the sound is for a dramatic effect! If I didn't want the sound; I could turn it off!

smitty wrote:Presumably, the Earth was subjected to the same "heavy bombardment" as the moon. Is is generally believed that (with some notable exceptions) evidence of this bombardment has been mostly washed away by our oceans, or what?

Yes, erosion and plate tectonics.
Oceanic crust is constantly being subducted and recycled, while continental crust is being constantly crushed, ripped and eroded.
Look at the Age of the Ocean Floor map.
http://www.ngdc.noaa.gov/mgg/image/imag ... -a0001.pdf
http://www.ngdc.noaa.gov/mgg/fliers/96mgg04.html
http://www.earthbyte.org/Resources/Ageg ... hrons.html

agulesin wrote:If "the Moon we know and love is as dark as coal", then how does it reflect the sun's light so well? I thought it was a sort of greyish colour... Having visited a coalmine I know how (non)reflective coal is...

As dark as coal (is it really?) but not necessarily with the same properties of coal. This is closer, at least for the maria.

Hey NASA scientists! Just a note from a retired NIH scientist: "history" is not the same as "evolution." Where is the replication? Where are the replicators? Where is the random variation? What were the selection pressures? Please. give me a break. You are perpetuating the misuse of the word "evolution" in the so-called modern press. It has been used repeatedly incorrectly to describe any form of change, including those, like your history of the Moon story, where evolution is not applicable. Your misuse trivializes the profundity of Darwin's insight. Wake up!

obscurechemist wrote:Hey NASA scientists! Just a note from a retired NIH scientist: "history" is not the same as "evolution." Where is the replication? Where are the replicators? Where is the random variation? What were the selection pressures? Please. give me a break. You are perpetuating the misuse of the word "evolution" in the so-called modern press. It has been used repeatedly incorrectly to describe any form of change, including those, like your history of the Moon story, where evolution is not applicable. Your misuse trivializes the profundity of Darwin's insight. Wake up!

Obviously the use of "evolution" was not in a biological sense in this instance. It has a variety of uses and your assertion that it trivializes any of Darwin's work is ludicrous.

Beyond wrote:
Hmm... kinda looks to me like the moon got hit in the face with a Big pizza pie

That's a Mare.

Obviously the use of "evolution" was not in a biological sense in this instance. It has a variety of uses and your assertion that it trivializes any of Darwin's work is ludicrous.

Ever try to teach evolution to a person who has a preconceived incorrect notion of what it is? This flippant use of the word "evolution" contaminates my students' brains, as well as the national discussion of science in general. I stand by my comment.

agulesin wrote:If "the Moon we know and love is as dark as coal", then how does it reflect the sun's light so well? I thought it was a sort of greyish colour... Having visited a coalmine I know how (non)reflective coal is...

Our eyes and brain stretch the brightest neutral colored object in our field to white or light gray. The only difference between the color of coal and of snow is intensity, not hue. The brightest parts of the Moon reflect about 15%, the same as freshly laid asphalt (which is bright enough that most people would prefer viewing it with sunglasses under the noonday sun). That's a lot of light against the black nighttime sky- which is why we see it as white and light gray.

Flase wrote:I believe the main reason the near side of the moon has many fewer impact craters is that it is tidally locked and the Earth makes a great shield. In order to hit this side of the Moon, an asteroid would have to come at the perfect angle past the Earth but not deviate too much.

The Earth provides hardly any physical shielding at all, being only a couple of degrees wide in the lunar sky (perhaps a bit more back then, as the Moon and Earth were closer). Indeed, the Earth may even gravitationally focus meteoroids, slightly increasing the bombardment from that side.

I'm not sure if it's clearly established that the Moon was tidally locked during the early bombardments. I've seen conflicting arguments. Obviously, if it was not yet locked, there wasn't even a lunar nearside to be affected by the Earth one way or the other.

But why did the volcanism stop if it was happening a billion or so years ago?

The Moon cooled down. Internal heat sources became deeper, so tectonic activity was reduced or ceased completely.

neufer wrote:

Beyond wrote:
Hmm... kinda looks to me like the moon got hit in the face with a Big pizza pie

That's a Mare.

According to Dean Martin, that's Amore.
"When the moon hits your eye like a big pizza pie, that's amore".
http://www.youtube.com/watch?v=aS6-b7CONDI

obscurechemist wrote:Ever try to teach evolution to a person who has a preconceived incorrect notion of what it is? This flippant use of the word "evolution" contaminates my students' brains, as well as the national discussion of science in general. I stand by my comment.

You sure there's something contaminating your students' brains? It's right there in the dictionary. In fact, the word existed and was used in other ways long before Darwin was born.

geckzilla wrote:You sure there's something contaminating your students' brains? It's right there in the dictionary. In fact, the word existed and was used in other ways long before Darwin was born.

Wow, you mean the word evolution evolved to include Darwin's Theory? I thought maybe he created it, kind of an intelligent design.