Skip to comments.Astronomy Picture of the Day -- Evolution of the Moon [ video ]
Posted on 03/20/2012 8:25:49 PM PDT by SunkenCiv
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.
(Excerpt) Read more at 220.127.116.11 ...
Vernal Equinox: This day and night are equal over all planet EarthSecond, the static graphics links:
Largest: maxresdefault.jpgThird, SunkenCiv again links his old post/topic regarding lunar origin:
Wow! Great graphics in the video.
I suspect that if the moon hadn’t blown off most of our crust we wouldn’t have continents and oceans.
I love astronomy.
I seriously doubt that the Moon was ever part of Earth. The only evidence for the conclusion thjat it was is the fact that the Moon is now very close to the Earth. But there are lots of moons in the solar system, many even larger than Earth’s. I never hear anyone suggesting that Titan came into being when a Mars-sized object slammed into Saturn. Or that Io or Triton came from within Jupiter or Neptune, respectively.
The whole Mars-sized object hitting Earth, knocking the Moon out, seems contrived to me. Why does it take a Mars-like impact to create the Moon? A more plausible explanation would be that the Moon was passing by and got caught in the gravity of Earth and is now a satellite. Not to mention the fact that there are numerous Moon-like objects scattered all over the known solar system. Jupiter’s four big moons, Titan, Triton, at least four large asteroids, and the planet Mercury, to name just a few.
Wasn't there a song about that in "The Sound of Music"? "How do you solve a problem like maria?"
Big question: if the moon is a satellite formed from ejecta of earth, just how did it achieve orbital velocity, and not just splash back down?
We all know you can shoot a rocket straight up into space, but there is a bit more involved making it an orbiting satellite.
It’s a chunk of stuff that flew off the earth as a result of a violent collision.
But it isn’t spinning round and round, as ricochet objects would.
And it is moving away from the earth at the rate of a few centimeters per year, instead of rather fast.
Do these NASA guys get paid big bucks to do this supposing?
I saw a display about the moon at the Air and Space museum 4-5 years ago, and it pretty much said that nobody is really sure how it was formed, exactly. I think some of the moon rocks do match some earth rocks, but I annot recall exactly. If something rally big, traveling really fast crashed into the earth, yes, I think the result could achieve orbital velocity.
There’s a prominent astrophysical theory (giant impact hypothesis) that supposes that there was a Mars-sized rocky planet(oid) that was in a very similar orbital pattern around the sun some few billion years ago. At some point the two bodies interacted, gravitationally pulling them toward and eventually slamming into each other. This impact threw off a moon-sized chunk that achieved orbital velocity and was joined to Earth.
Doorgunner, also keep in mind that we’re talking about an enormous mass of rock. Sure you would have a hard time putting a school bus in orbit on a permanent basis; the Earth is much more massive than a school bus. Every object’s mass affects the gravitational boundaries of another to some degree. The larger the two objects, the more likely they’ll orbit and eventually fall into each other.
Think of gravity like a big blanket. Place an object with the mass of the sun in the center, and you create a giant funnel toward the center. With the proper speed, a smaller mass object can ride along the inside of the funnel indefinitely. Now take that same blanket, plop and Earth-mass object on it, the same funnel is created, thus an object of lower mass could ride along the inside of that funnel. The larger the mass, the more likely it can achieve a velocity sufficient to keep it in orbit.
And don’t forget, the moon is actually moving away from the Earth at a rate of about 1.5” per year.
I also love astronomy. I’m not sure if we could ever prove the moon was or was not ever part of the earth. The early solar system was probably so chaotic anything might have happened. Proving it did or did not is another question.
I’m just glad it’s there; without it we probably would not be a life-friendly planet. And it feels good to howl at it at night.
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