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Study Explains Why Lunar Craters Are Bigger On the Near Side
An anonymous reader writes "A new study of asteroid craters on the moon has uncovered some big differences in the composition of the crust on the two sides of the moon. 'While massive impact basins pockmark the moon's near side, its far side contains considerably smaller basins. The discrepancy in crater distribution has puzzled scientists for decades. To investigate what may have caused this difference, the team obtained data from NASA's twin GRAIL probes, which orbited the moon from January to December 2012. During its mission, the probes circled the moon, making measurements of its gravity. Zuber and her colleagues used this data to generate a highly detailed map of the moon's crust, showing areas where the crust thickens and thins; in general, the group observed that the moon's near side has a thinner crust than its far side.'"
The only way to explore space is by sending people into a tin can in LEO. We can't explore space from our computer chairs.
The paper this press release is about doesn't seem to be online, but two papers from the past few months analyzing this GRAIL data (with some of the same authors) are available:
"Gravity Field of the Moon from the Gravity Recovery and Interior Laboratory (GRAIL) Mission", the initial report of the observations
"The Crust of the Moon as Seen by GRAIL", reconstructing the crust thickness and composition from the observations
10 PRINT CHR$(205.5+RND(1)); : GOTO 10
OK, there are larger craters because the crust is thinner on this side, but why is the crust thinner on this side? Mere happenstance, or is it caused by orbital mechanics or some other reason?
09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0
...but that one's far away.
Anybody else unaccountably hungry?
"Wait. Something's happening. It's opening up! My God, it's full of apricots!"
I would hazard a guess that if the core is more liquid than the crust then the Earth's gravity might tend to draw it towards the near side more when it gets hit on that side than the far side. Hits on the far side might be more restrained as there is not as much expansion pressure. Over millions of years the effect could become quite pronounced.
Just talking through my hat, of course, and probably full of it.
If the moon is cheese
Thin and original crust
Means it is pizza
fewer rocks strike the Earth facing side of the moon because the earth is in the way
Here's an interesting visualization of a possible early evolution of the solar system. It's a bit surprising just how sudden the late heavy bombardment event was.
If the Moon was created by a glancing collision between the Earth and a Mar-sized protoplanet, which seems to be the going theory nowadays, then the Moon was created in Low Earth Orbit during the very heavy bombardment phase of the LHB. Once the Moon became tidally locked -- which would have happened pretty quickly at such proximity -- Nearside was shielded from most further bombardment by the Earth. So Nearside is kind of a fossile from the heaviest epoch of the LHB, while Farside continued to get pelted as the big stuff was swept up, and finally got the fine dusting of the last scraps evening it out. It would also have continued to accumulate crud, which Nearside wouldn't, thus the thicker Farside crust.
Brackets contain world's first nanosig, highly magnified:[.]
only different. Southern hemisphere of Mars is something like six kilometres higher in elevation than the northern half. The Electric Universe people have a lot to say about such things - none of which involve impact events: hexagonal craters? Craters within craters? Crater chains?
All hail General Zed!
The percentage difference in thickness is enough to influence gravity at that distance to cause that many more strikes on that side? I call bs.
The number of strikes are probably about the same, but the thickness of the crust makes a huge difference on what happens when a meteor strikes.
Homework for next week: Fill a bucket with some flour, drop a ball in the bucket and observe the impact. Fill the same bucket with concrete to the same level as before and drop the same ball in the bucket. Is the impact the same as before?
Everyone knows the aliens on the dark side of the moon destroyed all the big ones before they hit their bases.
Wouldn't asteroids hit the moon a lot harder if they glanced past the earth, due to gravitational slingshot? Seems like a good reason for a bigger crater.
Wouldn't object's that hit the near side get a gravitational acceleration as they pass by Earth just before hitting the moon giving them, on average, a higher impact velocity?
The Earth-Moon system orbits around a point which is not at the center of the Earth, sort of like a barbell with small and large ends will balance on a point which is not in the center of the big end. The point of rotation is still inside the Earth, just not at the center of the Earth.
This is why we have two tides [roughly] each day - the side near the moon gets attracted to the moon, while the other side gets swung around on the outside and experiences centrifugal force, pulling it away from the center.
The moon should experience this same effect. I would expect tidal forces to draw mass away from the center, resulting in more mass on the far side.
When the earth and moon collided it was not a high speed affair, or at least not as high speed as most celestial collisions, and happened much later than most theories have it doing so. Part of the moons crust at the time peeled off during the collision and formed most of the land masses we now have on earth. Most of the detritus of the collision continued to rotate about the earth and moon causing many many meteor strikes on both planets. Like I said it's just a theory.
It's all dark...really
Are there any news of a monolith?
Gravity is not the only or the strongest force in the universe.
Most likely the craters were caused by plasma discharges, ie electrical arcs.
Too much to go into here. Do yourself a favor. Google "electric universe". Read the book "The Electric Sky".
A headline about big craters on the moon and not a single Goatse joke? Man, this place is slipping.
The chance of any object large enough to leave a crater visible from earth on the moon being shielded by earth, is very small. While the earth is roughly four times the diameter of the moon, it's at such a distance that it covers a very small part of the total area from which objects from space will hit it.
Just look at the sky at night at a full moon. Calculate roughly how much area the moon covers if it's high up in the sky and multiply the surface area by 8 (4^2 then divide that number by two because you only see half the hemisphere, high up in the sky because the atmosphere makes objects appear larger if they are close to the horizon). It may be easier to imagine the moon about 2.82 times the diameter it is to get to that size. Now picture yourself standing under an umbrella that size, pointed in any random direction and have a thousand people throwing rocks at you from all directions and all distances. How big is the chance that they'd miss because the umbrella would shield you?
You could do the actual math and not do a quick guesstimate like I just did to come up with the exact amount of hemisphere that would be shielded by earth from the moon and come up with a low percentage number. That would still not be the percentage of shielding that you'd get from earth, since the gravitational field will pull in stuff that would be in a trajectory to just pass earth. Some of it will crash on earth as a result of that, some of it will deflect the path such that it may just miss the moon and some of it will pull stuff in a trajectory that will hit the moon while it wouldn't have otherwise. Still, the amount of hemisphere being influenced positively or negatively by this field would be rather small, most of the rocks would just get through regardless.
The big thing shielding both earth and the moon currently are actually the bigger planets further out in our solar system. The main reason we don't get a lot of large objects hitting us is because most stuff getting into our solar system will start being in pulled slowly from outer belts of debris and intersect with one of the big planets gravity fields before they'd even get close. Most of the moon craters we see from here were formed long ago, when there way way more stuff flying around in our solar system, especially just after the crash that triggered the inception of the moon and it just had gotten it's shape. Earth has an atmosphere and tectonics that made any old craters disappear, the moon has kept them since it's inception.
I was promised a flying car. Where is my flying car?
See my comment elsewhere in this thread. The earth is only a very small part of the moon hemisphere. It's effectively a little less than three times as big "in the moon sky" and the rest of the hemisphere. It is actually about four times as big, but to make it easier, I'm also including the half of the hemisphere you can't see in the comparison how much it would shield you.
It's like saying a thousand people throwing pebbles at you simultaneously have less chance hitting your body because you are holding up a tennis ball. Maybe a few will miss you because their pebble will bounce off the tennis ball, but almost all will get through.
I was promised a flying car. Where is my flying car?
Speed times mass square. Nothing more, nothing less is what determines impact energy. Go look it up in your high school text books if you doubt this.
Distances from whatever other bodies have no significant influence whatsoever. They may slightly influence the speed at which the object travels with their gravitational fields, just as the gravitational field from the moon itself may increase the speed once an object is getting closer to the moon. Looking at what currently is flying around our solar system, almost anything is coming from the outer belts and is pulled in by the combined gravitational fields of all our planets and the sun. Anything not prematurely being sucked up by the big gas giants further out, has speeds of thousands of kilometres per second by the time it gets close to the earth and the gravitation fields from both the earth and the moon have no significant effect on the impact energy any more.
I was promised a flying car. Where is my flying car?
The stuff filling the larger craters were from the underground helium 3 factories created by the Nazi's on the back side of the Moon; the factories have made the surface appear thicker. The earthside is thinner from mining the rocks needed for the coming meteor blitzkrieg. What wrong with you people? Haven't you learned anything from history?
I imagine having the earth act like a gravity focus, greatly increasing volume of space and velocities that would have missed the moon completely... need to make a few diagrams to get this across well.
I can't see why this would not be pretty obvious.
Of course, I play Kerbel Space Program so have more intuitive feel for these systems.. buy it, learn it, teach it to your children. How else will they dodge space trash?
Wouldnt it made sense that some of the impacts on the near side would have just swung around the earth's gravity well and increase the energy of the impact?
So the near side has a N.Y.-style crust, while the far side has a Chicago-style crust. I vote we send a probe to measure cheese depth A.S.A.P.!
The percentage difference in thickness is enough to influence gravity at that distance to cause that many more strikes on that side? I call bs.
I think its roughly the same number of strikes but thiner crust means a bigger crater when they hit.