When Moons Collide They Form One

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When Moons Collide They Form One

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Astronomers believe that Earth once had two moons and they collided to form the satellite we see today.

The moon has long been a source of fascination for druids, night elves and just about everyone else. Ancient humans attributed god-like - or goddess-like - qualities to the silver orb and modern man walking upon its surface still evokes patriotic feelings. The dark side of the moon has mystified both Pink Floyd and astronomers alike because once they saw pictures of it 1959, its high mountain peaks were very different from the low plains of volcanic rock that make up the hemisphere that faces the Earth. Scientists now believe that disparity derives from the fact that Earth once had two satellites and the pair of moons crashed together to form what we see in the sky today.

The study published in the August 4th issue of the scientific journal Nature by a collaboration between Erik Asphaug from the University of California, Santa Cruz and Martin Jutzi at the University of Bern in Switzerland reports that computer simulations reveal that the Moon would not only survive such an impact but it would account for the different makeup of both hemispheres.

But how would two moons suddenly collide in orbit without falling to Earth? Well, the answer to that question involves a concept called Trojan points. Imagine a equilateral triangle with the Earth and the Moon at two points. The third point a Trojan point and it is possible for a body to orbit the Earth in that position without crashing into either of its neighbors. For a while.

"It is entirely plausible for a Trojan moon to have formed in the giant impact [that created the Moon to begin with], and for it to go unstable after 10 million to 100 million years and leave its imprint on the moon," said Asphaug. He said to think of the impact as "a ball of Gruyere colliding into a ball of cheddar."

The second moon would have had to have been much smaller, about 750 miles in diameter and a mass about 4 percent of the Moon. Because the orbit decayed over time, the second moon would impact traveling relatively slowly - 4,500 to 6,700 miles per hour - and the result would essentially cram the rock and minerals of the second moon onto the Moon's surface like smashing two pieces of soap together to form one bar.

The theory of a second moon does has some detractors, even from Asphaug's own colleagues at UCSC. Francis Nimmo thinks that just gravity is powerful enough to create the highlands of the dark side of the moon. "As further spacecraft data and, hopefully, lunar samples are obtained, which of these two hypotheses is more nearly correct will become clear," Nimmo said in reply to Asphaug's research.

Sounds like an astronomy gang fight is in order. Someone close the observatory for the night and sharpen your telescopes. The only way to see which theory reigns supreme is to settle this like men. Two astronomers enter, one astronomer leaves! Two astronomers enter, one astronomer leaves!

Source: Nature via Space.com

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Excellent pic choice.

Anyway, I find this theory INCREDIBLY difficult to believe unless this happened very early in the Moon's lifetime.

I can't think of anything to say except...
I think it's marvelous! HaHaHa!

Reading the article myself I marvelled at how astronomers view the world - those two moons supposedly crashed into each other at a "very slow" speed of 25 kilometers per second, or a good 5000 miles per hour.

Judging by the wording that wouldn't be enough for a planetary speeding ticket.

Kargathia:
Reading the article myself I marvelled at how astronomers view the world - those two moons supposedly crashed into each other at a "very slow" speed of 25 kilometers per second, or a good 5000 miles per hour.

Makes you wonder why people can get done for 'speeding' at such lethargic speeds such as 100 kilometers per hour, doesn't it?

Anyone else hungry for cheese, now?

Also, I wonder how much differently both the Earth and human history would have come out if we'd had two moons instead of one. Tides would likely act much more differently, for one thing, and who knows what sort of early mythologies we would have come up with to explain two circles in the sky instead of just one?

Is this new news i am sure Scientists have been saying this for years or did i fall through a gap in time again.

It's a cover up. The second Moon was a giant space canon destroyed by Optimus Primal to save the planet from obliteration.

I thought the current theory was that a mars sized object collided with earth, and the debris gathered into the moon?

Either way, we now know wthat the moon has a history of colliding with stuff... It's only a matter of time...

DAWN OF THE FIRST DAY...

Jabberwock xeno:
I thought the current theory was that a mars sized object collided with earth, and the debris gathered into the moon?

Not only that, but this collision was used to explain why the Earth's axis of rotation is 23 degrees from vertical - it was knocked sideways by the collision. If this theory is discarded then they'll have to find other reasons for the seasons.

I'm not going to argue with them though, they're cleverer lads than I.

So... that pink floyd cover gains some type of fantastic scientific relevance does it?

Jabberwock xeno:
I thought the current theory was that a mars sized object collided with earth, and the debris gathered into the moon?

That's part of this theory. They also believed that same collision could have created a smaller moon which eventually crashed into the bigger one.

Greg

ok, if the earth was once a moon, what was it orbiting? Earth orbits the sun becuase its a planet, but a moon needs to orbit something that isn't a sun. What were these moons orbiting?

Eekaida:
ok, if the earth was once a moon, what was it orbiting? Earth orbits the sun becuase its a planet, but a moon needs to orbit something that isn't a sun. What were these moons orbiting?

They're theorizing that Earth once had two moons, not that Earth was a moon.

According to QI the Earth still has two moons.
And i consider everything Stephen Fry says to be true regardless of context or likelihood

AND NOW SOME SCIENCE!

supermariner:
According to QI the Earth still has two moons.
And i consider everything Stephen Fry says to be true regardless of context or likelihood

There's actually more (which they also mentioned on later shows).

While none of them are on the same scale, both physically and scientifically as the Moon, they are in fact large bodies that orbit Earth, by definition a satellite, which the Moon is also.

There full names are:

- 3753 Cruithne
- 2002 AA
- 2003 YN
- 2004 GU
- 2010 SO16

http://en.wikipedia.org/wiki/Earth#Moon
http://en.wikipedia.org/wiki/Quasi-satellite

Of course that doesn't sound very poetic. "When the 2010 SO16 hits my eye like a big pizza pie, that's... erm... complex astronomy."

Jabberwock xeno:
I thought the current theory was that a mars sized object collided with earth, and the debris gathered into the moon?

Either way, we now know wthat the moon has a history of colliding with stuff... It's only a matter of time...

DAWN OF THE FIRST DAY...

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I mean, now everyone will be spouting Legend of Zelda sayings...........

OT: obviously the only way we will be sure of what happened is to build a giant moon base for people to live in.

GET TO WORK SCIENCE!

There is no dark side of the moon, really.

I saw the picture an immedately started listening to "The Great Gig in the Sky"

OT:Now, It seems possible, but I think there are better theories than "We had two moons once." Whatever. I'll wait until science proves it one way or another.

Kargathia:
Reading the article myself I marvelled at how astronomers view the world - those two moons supposedly crashed into each other at a "very slow" speed of 25 kilometers per second, or a good 5000 miles per hour.

Judging by the wording that wouldn't be enough for a planetary speeding ticket.

I studied geology for a while at university. Whenever we talked about anything "recent" it usually meant in the last million years. I know exactly what you mean, its all about perspective

Richardplex:

Kargathia:
Reading the article myself I marvelled at how astronomers view the world - those two moons supposedly crashed into each other at a "very slow" speed of 25 kilometers per second, or a good 5000 miles per hour.

Makes you wonder why people can get done for 'speeding' at such lethargic speeds such as 100 kilometers per hour, doesn't it?

It is because it is in relation to how everything else in the universe moves. A lot faster. Plus when you have the amount of empty distance between things as you do in space 25km/s isn't all that fast.

OT: The only way I would even believe this theory is if they took samples from the other side of the moon and it was like some completely different kind of material, or was carbon dated to a completely different time.

The Rogue Wolf:
Anyone else hungry for cheese, now?

Also, I wonder how much differently both the Earth and human history would have come out if we'd had two moons instead of one. Tides would likely act much more differently, for one thing, and who knows what sort of early mythologies we would have come up with to explain two circles in the sky instead of just one?

Ahem... Three, not two. There is that big burning circle (square for minecraft fans) in the sky during the day.

Anyway I definetly recall hearing an astronomer talking about this on the radio a couple of weeks ago.

Also I want a toasted cheese sandwich now.

So that's what happened two moons entered and one moon left.

Granted sometimes I don't pay attention to some of the articles from week to week, but I have to say... I rather enjoy these few non game related articles of scientific interest.

I hope more at too come from time to time.

Actually just to throw that out. Wasnt it also been claimed once that our moon is actually another planet altogether that collided with the Earth itself and basicly jumpstarted the whole evolution of life? And the Moon as it is today is just the remnant of that other planetoid?

At least i seem to recall something like that from..last year or so. And now they are claiming its collided with the "original" Moon basicly? Ehr..meh. Honestly i think the big craters and all are meteroid impacts. Its a fact that the biggest ones get swallowed by Jupiter or any of the other high gravity planets (Jupiter is only the biggest aside from the sun in terms of pure gravity) between the edge of our solar system and Earth. Everything else basicly tends to get caught by our Moon. Hence while it also causes the tides and all that, its basicly our natural shield. The Meteor that wiped out the Dinosaurs was basicly one of the lucky ones to get through, a lot either burn up in the atmosphere, get eaten by jupiter or just smack into the moon.

Froken Keke:
There is no dark side of the moon, really.

Thread winner. I had that quote going through me head the whole time I wrote this post. That's why I used that image.

Greg

Jabberwock xeno:
I thought the current theory was that a mars sized object collided with earth, and the debris gathered into the moon?

Either way, we now know wthat the moon has a history of colliding with stuff... It's only a matter of time...

DAWN OF THE FIRST DAY...

Well actually the moon is getting farther away from the Earth so that's unlikely.

I really don't see this as being plausible...

if there was a collision, we'd see tons of particles and debris in orbit. we'd also see an asymmetric shape.

the reason the "dark side" looks and is composed differently is because it gets hit by meteors and asteroids. can't get hit on the inside very easily...

Coffinshaker:
I really don't see this as being plausible...

if there was a collision, we'd see tons of particles and debris in orbit. we'd also see an asymmetric shape.

the reason the "dark side" looks and is composed differently is because it gets hit by meteors and asteroids. can't get hit on the inside very easily...

actually, if you shoot 2 bullets together and they hit(as in shoot from opposite directions so they collide mid air) it molds into 1 thing

and mythbusters did this thing with steel if there is a large enough explosion the 2 pieces will mold into 1 piece

so its plausible based on that stuff

EDIT: mythbusters video below

http://www.youtube.com/watch?v=fGi0w7ycRKk

Shouldn't the headline read "some astronomers"? A blanket "astronomers" sounds like there's a scientific consensus already on the issue, which there isn't; it's a "hey, *maybe* this happened" hypothesis newly proposed by a team of two which needs (lots of) further investigation and research to be upgraded to "yes, this was near-definitely the case."

I opened this listening to Dark Side of the Moon. Aw yeah.
Then again, I always listen to Dark Side of the Moon...
Cool stuff, scientists!
Here, have a happy crater
image

Well, we really dont have enough proves for this theory, not yet at least. And im much more willing to believe about the gravity than this really. gravity is more powerful than most people think.

Spygon:
Is this new news i am sure Scientists have been saying this for years or did i fall through a gap in time again.

I agree. This theory is not new, I've been told this happened since primary school decades ago!

Old theory is old! Im guessing some new paper has been released recently to bring this one back into the limelight.

I recall reading somewhere on the two moon theory that some of the debris peppered the earth and helped create some more of the more interesting landscape features that couldn't easily be attributed to plate movement and the likes.

It would be nice if one day we did master time travel to the extent of at least being able to send a camera back of to the begining of earth and let it record all this. You could send a camera back to key points through history then just pick up the cameras present day.... just need to alter our laws of reality to allow time travel :D

If it was gravity, wouldn't the mountains be facing earth? I would have thought the dark side would be flat, and the earth facing side mountainous.

And it does seem to make sense to me at least, splat a 750 mile wide moonlet onto the the moon and it'd do some serious ground leveling.

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