Starship Asterisk*

Where are ANY of the impactors?

When one looks at all the images of cratered surfaces there is something that seems to be missing. Often when researching images it isn't what you can see or don't see, but what one should see and yet it isn't there.

After years of researching craters, learning what scientists say about them and their formations, there remains one nagging question; Where are any of the impactors? The odds of all these craters we see not showing any impactors is virtually impossible. If it is true that all these craters are caused by impactors there should be many that show the impactor that caused it.

http://antwrp.gsfc.nasa.gov/apod/ap060530.html

The assumption that all impactors were traveling at velocities fast enough to disintegrate the impactor is impossible. The fact is that these objects traveling about our solar system and impacting the surfaces of planets and moons are not all going at "hyper velocities". All known meteors that have hit earth have never caused a crater, only holes in roofs, dented vehicles, and damaged printers. All of the other craters that are said to have been caused by a meteor here on earth is only an assumption, not a fact.

http://antwrp.gsfc.nasa.gov/apod/ap990711.html
http://epod.usra.edu/archive/epodviewer.php3?oid=186400

Norval

craterchains wrote:Where are ANY of the impactors?
All of the other craters that are said to have been caused by a meteor here on earth is only an assumption, not a fact.

http://antwrp.gsfc.nasa.gov/apod/ap990711.html

Norval

How are these assumptions? Isn't there large peices of melted/molded iron from impactors that caused the crator in Arizona?

Generally in Terrestial craters you do find evidence for the remains of the impacting bodies, its in shocked quartz grains and grass fragments, these usually contain element abundance ratios that dont match any on Earth, but do match those of comets or asteroids. The famous iridium layers found in geological layers associated with the impact that may have had something to do with wiping out the dinosurs is a good example of this.

I'm not sure what your actually driving at, but in general the objects that have caused the damage you describe are considerably smaller than objects that cause major craters, which are fortunately very rare after 5 Billion years of impacts.

The reason in general you dont see impactors, is because they ave either been totally destroyed, or later erosion/geolocigal activity has covered them. On the moon they would tend to get covered by the layers of dust created by smaller impacts.

What do you suggest created the craters?

An interesting item about melted glass in craters, Dr. Shoemaker was investigating the glass in Wolf Creek Crater and Barringer Crater compared to the nuke testing crater glass when came about his unfortunate accident.

Anonymity is one thing on the internet but I prefer to know a bit about those I am posting with so, this is my only post to Wadsworth and Astro_UK, without knowing who I am posting too since your profiles are blank. Just who are you, just a little bit about yourself.

I'm really not sure what you're driving at; If you're just curious or think everyone is missing something obvious. I think we can safely say those craters in the first picture didn't come from B-52's carpet bombing aliens on Rhea out of existence. For one, the craters are too big for that.

Which leads to my point. You're looking at all the big craters. NASA has estimates of critical impact energies for various materials, above which the impacting object can not survive, except perhaps as very small chunks which are hard to distinguish from the far greater amount of ejecta. The very fact that those craters are in most cases dozens of miles across shows that they were formed by high energy impacts.

So why one rock and not the other? Drag. The smaller a body, the higher the ratio of its surface area to its mass. The more surface area, the more atmospheric drag. The more mass, the more momentum to be overcome by drag. As a meteor or asteroid enters a planets atmosphere, the two factors are competing: drag to slow the object down, momentum to maintain the velocity. So, the big rocks, with a low ratio of drag to momentum, are able to carry significant portions of their momentum all the way to the surface, where they hit really hard and are pulverized or even vaporized. Smaller rocks, with high ratio of drag to momentum, are slowed significantly, sometimes even to their terminal velocity (the speed at which the attraction due to gravity is equal to the drag force) of only a couple hundred miles per hour.

Of course, in the case of our moon or of Rhea, there is effectively no atmosphere, so pretty much any impact can be expected to occur at high velocity, except in the fairly rare case that the impactor is on a very similar orbit. Ergo, the odds of an impactor surviving on a planet with no atmosphere are low.

Also, as astroUK mentioned, Erosion is also a factor and some impactors may survive but later be covered up. Again, however, we don't expect an impactor to both survive and make a large crater. If you're interested, one of the Mars rovers may have actually found a meteor that survived, and was later completely uncovered by wind erosion. Check this out:

http://www.newscientistspace.com/channe ... ers/dn6883

Hi FieryIce

My name says it all, I'm a professional astronomer based in the UK. My specialism is mostly related to the formation of Early Type galaxies and star clusters. Anymore information than that is irrelevant.

craterchains wrote:Where are any of the impactors? The odds of all these craters we see not showing any impactors is virtually impossible. If it is true that all these craters are caused by impactors there should be many that show the impactor that caused it.

From http://www.amnh.org/exhibitions/permane ... s/impacts/:

Many fairly large meteorite samples were buried at the bottom of small craters measuring no more than two meters (6.5 feet) across. Larger craters, on the other hand, usually contained many very small meteorite fragments.

But the researchers knew that larger impacting meteorites must have made the larger craters. These meteorites apparently landed with so much kinetic energy that they shattered into tiny fragments.

This makes sense: the intermediate formation between a small space rock freefalling and bouncing off the ground and a large impactor that mostly vapourizes leaving a huge crater is a small, mostly intact impactor resting in its own small crater.

craterchains wrote:The assumption that all impactors were traveling at velocities fast enough to disintegrate the impactor is impossible. The fact is that these objects traveling about our solar system and impacting the surfaces of planets and moons are not all going at "hyper velocities".

Depends on what you consider to be "hyper velocity". An object falling to Earth from far away would hit at a minimum speed of 11.2 km/s, or just over 40 000 km/h - the planet's escape speed. If the Moon were alone in space, objects would still impact at a minimum of about 2 km/s, which is a rather fast clip; in reality, these objects gain additional speed form Earth's presence. The same goes for the moons of gas giants. Check the kinetic energy of an object moving at these speeds - it isn't small. A 1-ton object moving at just 2000 m/s has 2 gigajoules of kinetic energy, or about half a ton of TNT. How big a crater would that leave?

craterchains wrote:All known meteors that have hit earth have never caused a crater, only holes in roofs, dented vehicles, and damaged printers.

Atmospheric braking. From http://www.meteorobs.org/maillist/msg21 ... [quote]The atmosphere does not brake such a body [as massive as the one that caused the Barringer crater] by much.

Little boulders from space are different, though. The atmosphere slows them down in one way or another. They are either totally destroyed, or else brought to a halt. An orange-sized rock would be decelerated by the time it reaches a height of 20 miles. From there it gets to the ground
under free fall: it plummets at the same rate as an object dropped from a
plane, reaching a terminal velocity of about 200mph. [/quote]

Did I just feed a troll?

EDIT: I posted before seeing iamlucky13's post, which answers the original poster very well.

Who cares? I just learned something.

What I find interesting about this particular creater is the fact that it is Square when viewed from above.

http://antwrp.gsfc.nasa.gov/apod/ap990711.html

Hi FireyIce

I updated my profile to show my occupation and where I currently reside.
I don't understand, does that make you feel more comfortable responding to my posts??

Well it may make him feel better wadsworth but I will no longer thread with you because your from TEXAS -Damn texans -

Well, not much in the way of thoughtful responses, so far. I sincerely hope there will be better responses forth coming. The fact is undeniable, there have NEVER been any "recorded" meteors strike earth that have made ANY craters. All of these larger craters are only "assumed" to have been caused by an impactor. This is an admitted fact by all who have posted so far.

Regardless of speed, size, or makeup where are any impactors? KNOWN impactors?

Elements from off earth are obviously from something that did cause the crater.
Fact; bomb casing fragments are recovered in just approximately the same amounts.

Fact; a half ton (1,000 lb.) bomb landing on rock mostly only leaves a flash mark.

After looking at many thousands of craters I have yet to see one impactor. That, in any reasonable odds is, impossible. Another fact.

Well, what else can make big craters, melt glass into a certain spectrum and fracture?

Keep thinking. Oh, yes it is most interesting that Barringer is very "square". Many other craters in our solar system display odd shapes also, but still no impactors showing.

Norval

Hi All

I don't really see what your problem with all this is Craterchains.

I think your problem is that in the course of human recorded history no one has seen an impact make a hole on Earth. But this clearly is not a problem, there simply arent that many large objects left in the vicinity of the Earths orbit, they've all been swept up, whats left is generally too small to reach the surface, and even when they do their generally puny. This is fairly fortunate because we wouldnt be here if the impact rate was higher.

Then there is the fact that we see impacts on the moon regularly that create craters, check out for a very cool video.

http://science.nasa.gov/headlines/y2006 ... oradic.htm

So unless the Earth is a special case, I still dont see what your driving at.
Are you saying that if you drop a rock the size of everest on the Earth it wont do any damage? Because the statistics of the Earth entirely avoiding any impacts that large throughout the last 4.5 Gyr are far more compelling than your "That, in any reasonable odds is, impossible. Another fact."

So why dont you just come out with what your getting at?

craterchains wrote:Well, not much in the way of thoughtful responses, so far. I sincerely hope there will be better responses forth coming.

Wow. May I suggest you attempt to answer the responses to your original post? Simply ignoring them like this really doesn't help your position and makes you sound like a troll.

craterchains wrote:The fact is undeniable, there have NEVER been any "recorded" meteors strike earth that have made ANY craters.

Did you hear about te Norway meteorite sighting earlier this summer that was photographed and set off seismographs? A couple of Norwiegian sources:
http://www.aftenposten.no/english/local ... 346411.ece
http://www.astro.uio.no/ita/nyheter/ild ... eball.html

It hit on Wednesday, June 7, around 2:00 AM, meaning that it was still 6/6/06 in the Western Hemisphere. Satanic alien planet-killers. Interesting. Only problem is they can't seem to find a crater for it http://www.aftenposten.no/english/local ... 353224.ece

craterchains wrote:fact; a half ton (1,000 lb.) bomb landing on rock mostly only leaves a flash mark.

Where did you get this information? Also, define "mostly".

craterchains wrote:After looking at many thousands of craters I have yet to see one impactor. That, in any reasonable odds is, impossible. Another fact.

That actually doesn't sound reasonable at all. Sounds like you've got a conspiracy theory. What, are craters remnants from iridium-based bombings carried out during an epic war raging throughout the entire solar system? I guess the solar wind is an ancient meteor defense system, too. And don't tell me there aren't obvious military applications for this "weapons cache" of meteorites stored in a convenient orbit around a gigantic fusion reactor.

astro_uk, that's an awesome movie. From the article, the impact only lasted 0.4 seconds! Meteor showers give the Moon a faint sodium atmosphere and tail: http://spacescience.com/headlines/y2000/ast26oct_1.htm

I know, its pretty damn cool. They have caught several apparently

I just keep thinking they must have plenty of disk space, if their watching
the moon that often with enough time resolution to pick that out. Still the guys working on the new survey instruments will be producing Terabytes a night.

Considering the lowest velocity an object large enough ignore the Earth's atmosphere has when it hits is around 11km/s, I fail to see how they're going to leave any significantly large remnants behind.

That said, Barringer Crater and the region surrounding it is (well, was) covered in scattered, small meteoric iron fragments. So... what's this about missing impactors?

I was actually wondering if Spirit and Opportunity found any impactor remnants on MARS. 'd love to get invited to a Steve Squires press conference and ask that very question. Pass the ice cold one, please !

Astro_uk, you may say what you are, that doesn't make it a fact with out the evidence to show it to be true. So, to me you are just another poster in a forum for now. Also, degrees do not impress me. They only impressed the person that tested your knowledge on what they wanted you to learn. But, as to your points? "Because the statistics of the Earth entirely avoiding any impacts that large throughout the last 4.5 Gyr are far more compelling than your "That, in any reasonable odds is, impossible. Another fact."
Very true. Now how do you think that is possible, that we haven't been struck, as other near by planets and moons obviously have been in more recent times? 8)
"So unless the Earth is a special case, I still don't see what your driving at." (Give it time. You may figure it out.) What I would give to have a Mars Orbital Camera around our moon. (Fat chance of that)

Pete (the student in Canada), at least these links you posted worked.
Bolides are also an interesting study.
"fact; a half ton (1,000 lb.) bomb landing on rock mostly only leaves a flash mark."
Where did you get this information? Also, define "mostly".
Answer; Experience, and being a Viet Nam vet helps, mostly. (Note your last link is a good example of explosives reacting on rocky areas.)

Qev, by all means, please remain anonymous. Keep thinking though.

ta152h0, hey hommie, hands yah a slushy cold Fish Tale Ale from Oly, enjoy.
It is true that "the scientists" are thinking some of the boulders on Mars could be meteors, but show me an impactor in any kind of depression that made that depression. Hell, I would settle for a few secondary impactors showing up in their supposed craters they made.

Norval

A few possible crater facts

excerpt:

Why does the Moon have so many craters while Earth has so few?
On Earth, impact craters are harder to recognize because of weathering and erosion of its surface. The Moon lacks water, an atmosphere, and tectonic activity, three forces that erode Earth's surface and erase all but the most recent impacts. Approximately 80% of Earth's surface is less than 200 million years old, while over 99% of the Moon's surface is more than 3 billion years old. Essentially, the Moon's surface has not been modified since early in its history, so most of its craters are still visible.
http://www.lpi.usra.edu/education/explo ... ring.shtml

Does the earth get "bigger" as time goes on ? like a mile per million years ? So early craters get buried and churned up by volcanic activity ? Earth must be an accretion sphere over millions of years.

Hello All

See link

Earth Impact Data Base
http://www.unb.ca/passc/ImpactDatabase/austr.html


As some have already stated erosion and growth and movent has hidden many craters.

Also as BMAONE23 stated that 80 % of the earth is about 200 million years old. This is because of the oceanic plates recycling much quicker than the continental plates.

Craterchains, you come off sounding just a little like you a complex there. But regardless, the fact is that there are some subjects nowadays that are so complex that you cannot get by without training, Physics is definitely one of them.

But maybe I'm wrong, you probably have your own home built anti-matter power plant, and you never even finished high school etc etc.

The problem Physics in general has is that it attracts cranks, generally because they have never heard of theories of chemistry or economics but have heard of Einstein, and much of what you learn from Physics is counter intuitive. Without a basic education in it you have no way of knowing where the real science is (BB for instance) or the crank science begins (young Earth creationism which I would guess you go for). You wouldnt allow a self taught Surgeon to operate on you so why is Physics teaching any different.

What always astounds me about cranks is that they happily accept all the modern successes of physics, like the PC im writing this on, but are also desperate to prove a theory that would make a device such as this impossible.

The Earth has been struck recently, by smaller objects that rarely reach the ground, the Earth has almost cleared its orbital environment. The only things that are really a risk at this point are comets which can swing in randomly, but the Earth is a fairly small target and its gravity is relatively small so its Jupiter that tends to get hit by objects like that. The chances of Earth being hit are therefore very small this late in the game.

(Just an excuse to post this)

http://hubblesite.org/newscenter/newsde ... 34/image/a

Cant seem to find the movie anywhere.

BMA
Thank you, and noted, nothing new to me though.

Ta152h0
See below. *

Harry
See below. *

Astro_uk
Not to just taunt you Astro, and your posting tactics are nothing new, but to remind you that most of the greatest discoveries and inventions came from those with little or no formal education. Your failure to properly address the quest for proof of impactors making all these craters, sadly remains.

* Earth is but one place for craters, lets move on to our Moon and Mars shall we?
Can anyone show me what I ask for?
After years of crater research, the simplest fact remains, no impactors showing. That I find mostly, intriguing.

Norval

I think you will find that most great discoveries of the last 200 years actually came from people who did have a great deal of formal education (for the time period in which they lived). The only counter example that springs to mind is Srinivasa Ramanujan, I'm sure you have a few other though, I'd be interested to hear them.

Inventions you may have a point there, if you mean dustbusters or whatever. Perhaps you can name a vital piece of technology from the last 100 years that was invented in someones shed.

As I and many others have patiently pointed out here there are many known remains of impactors, but I think your still hung up on some size issues. As an obvious example of why you dont tend to see the remains of impactors, what do you suppose is left behind 100 million years after a comet hits something? A big lump of ice? Or a hole that the big lump of ice made as it was vapourised.
Another important point is that asteroids and comets, are very rarely solid objects in the sense that we think of it, their density usually reveals that they are fairly porous, making it likely that after impact very few large sections are left.

As for the moon, I showed you a crater being formed on the moon what more do you need?

astro_uk wrote:I think you will find that most great discoveries of the last 200 years actually came from people who did have a great deal of formal education (for the time period in which they lived). The only counter example that springs to mind is Srinivasa Ramanujan, I'm sure you have a few other though, I'd be interested to hear them.

Inventions you may have a point there, if you mean dustbusters or whatever. Perhaps you can name a vital piece of technology from the last 100 years that was invented in someones shed.

As I and many others have patiently pointed out here there are many known remains of impactors, but I think your still hung up on some size issues. As an obvious example of why you dont tend to see the remains of impactors, what do you suppose is left behind 100 million years after a comet hits something? A big lump of ice? Or a hole that the big lump of ice made as it was vapourised.
Another important point is that asteroids and comets, are very rarely solid objects in the sense that we think of it, their density usually reveals that they are fairly porous, making it likely that after impact very few large sections are left.

As for the moon, I showed you a crater being formed on the moon what more do you need?

Where has all the logic and critical thinkers gone in this world?