The general consensus of scientists is that these were caused by a “tidally disrupted comet” like comet SL9.

I question that theory based on the following.
1. They are too uniform in spacing.
2. They are too uniform in size.
3. They are too uniform in that they all hit simultaneously.
4. That an object would have to have broken up into equally sized pieces, with no smaller chunks defacing the main impacts, and impacted simultaneously so as no ejecta material falls back into the adjoining craters of that chain.
5. What are the odds of that ever happening, let alone as many times as we can see from space photos?

Just based on tossing hand full after hand full of marbles which are all the same size I have still to get even 4 to land in a reasonably good line just touching each other let alone 50 all in a line equally spaced.

Could this be a sign or signal that SETI missed?
I just don’t think they could happen naturally. [-(

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http://www.craterchains.com/ns/nspage.html

I don't understand this step. Why would they have to impact simultaneously, and why would that prevent ejecta material falling into the others?

Based on the pictures I saw, I supose tidally disrupted comets are already in line formation.

You saw that the fragments of SL9 formed a straight line. Do you think that SL9 broke up that way naturally?

This is incmplete rather than incorrect. Other explanations for crater chains include secondary impact for other craters and collapse of lava tubes (possibly due to impact at different times). Interpretaion depends on the geology and morphology of what you're looking at. There are specific clues to look for that would lead interpretation toward or away from one or the other of these possibilities.

As for your observations, as they are stated, we have no idea of the sample set or analyses you used to inform your assertions. Do you have size-frequency distrubutions of a large set of these crater chains? I'd love to see your data if you can show me quantitatively that a) in any given chain all craters are "the same size" (within 1%? 10%?); b) in any given chain all craters are spaced "evenly" (distances within 1%? 10%?); c) that a) and b) are true for some significant portion of crater chains (1%? 50%? 95%).

a) could easily be true for some chains if they are structurally constrained during formation; by a flow channel, for example.

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Electrical scarring anybody? :wink:

Any pics, links?

Marbles aren't gravitationally attracted to each other, or at least not enough to matter. They also didn't start from a single object with a common velocity and acceleration. So your example is completely off base.

A random distribution of marbles is nothing like an object that comes apart in orbit.
Yup. Aliens travel across our galaxy and try to signal to us by crashing asteroids into planets and moons. :roll:

Crater chain at APOD.

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why wouldn't they hit in a straight line and more or less evenly spaced? given an object with a certain speed and direction, pieces falling off that object would all have the same speed and trajectory/direction. just compare it with bombs being dropped from an airplane.

you'd expect this pattern from an object that falls apart (not from one that explodes violently, granted, but that is, i think, not what is being suggested).

as for the pieces all hitting the ground at the same time, well, i thought the law of gravity sort of made that a condicio sine qua non, given equal speed and no additional acceleration.

[edited for typo]

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Hi,

Here's my first impressions (no pun intended) of your ideas - I'll answer between each number on your list - just for fun: :wink:

1. They are too uniform in spacing.
There's no mechanism forbidding naturally occurring uniform line impacts.

2. They are too uniform in size.
Judging from Shoemacker-Levy 9, uniform size impacts can occur naturally.

3. They are too uniform in that they all hit simultaneously.
Simultaneous impact is possible, but given the tendency of Jupiter's gravity well to disrupt a comet, the nature of comets, and the locations or uniform impacts, they could all hit in sequence or all at once.

4. That an object would have to have broken up into equally sized pieces, with no smaller chunks defacing the main impacts, and impacted simultaneously so as no ejecta material falls back into the adjoining craters of that chain.
But are there not ejecta around each member of a crater row?

5. What are the odds of that ever happening, let alone as many times as we can see from space photos?
Not sure what you're asking here. It happened because we see rows of craters today. It is believed that there was a period of frequent impacts in the early solar system. Many crater rows likely date from that time, and we saw one created (temporarily) on Jupiter.

Rows of craters seem like a very spectacular natural occurrence to me. Aliens need not be involved, please.

One of my favorite odd crater pairs exists on the moon. Just two craters next to each other. On slopes one way, the other slopes the opposite way, with some ejecta sprayed out in opposite directions. It is theorized that an object came in at a shallow trajectory, impacted a hill, barrowed under the soil and exploded out the other side. (Does anybody remember the name of this lunar feature?)

Excellent analogy!

Nice example. Notice that the craters are neither uniform in size nor evenly spaced.

Milli360
Scientists observations note that these types of crater chain (close inline craters that form a chain) had to have hit almost at the same time because the ejecta didn’t fill in or deform the other craters. The forces of the simultaneous strikes (explosions) causes the ejected material to go side ways and not lineally.

Jairo – Tofu – Soupdragon2 – Aurora – Morrolan – Chip, and JohnW
You may want to look a bit closer, SL9 was not of equal sized pieces, nor in any kind of line that would cause a crater chain like we are interested in. Electrical scaring was a possible. Crater chains would be a lasting mark of “We were here.”. Look at many other pictures of the crater chains and compare them.

Eye-Zee
Given the locations of all the crater chains that pictures are available for, along with the known physical data of the strike areas, the obvious possible causes are narrowed down considerably. It is also noted that the small variations in size of some of the craters in the chains could be due to the density and general geo-morphology of the surface being impacted. There is a noted pattern in some chains that seem to show that the ends are tapering slightly, the craters becoming smaller in diameter, yet still rim to rim in spacing.

There appears to me that there are hundreds of these types of crater chains so far photographed in our solar system. Unfortunately, there are only about a third of these photographs available on the net. The rest are mentioned in some of the reports on the web. Based on what has been seen and the given data on the net the uniformity of these crater chains is easily with in 5% +/- range. There are crater chains with 40km wide craters down to as small as the images can show, a few meters in diameter. At this point with 3 years into the investigation of these types of crater chains it is quite apparent that based on 4 or more aligned and uniform sized and spaced craters with a differential of less than 10 %, and eliminating other possible causes. The remaining explanation being from a primary impact for each crater in the chain hitting almost simultaneously. Be that from a broken up space rock or what ever, or? We are left with an incredible amount of these types of crater chains all over our solar system, on almost every body so far photographed, with Mars and Phobos having the most per given area. Based on the given information I think there should be some deeper investigations and research on these types of crater chains.

Good reply, thanks. Hope you find this as peculiar as I have.

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http://www.craterchains.com/ns/nspage.html

SL9 was just one example - the only one we've been lucky enough to actually see happening. There were a lot more things flying around in the early solar system. While most of them were solid enough to cause single impact craters, it's entirely plausible that some would have been broken up by tidal action on the way down. We know that this can happen to comets, and we also know that some asteroids are loosely-bound heaps of rubble, not solid rocks. It's not surprising that crater chains are rare compared with the number of single-impact craters, but I don't think we need to invoke alien civilisations as their most likely cause.

Could you post links to a few examples? The one posted by jt-3d doesn't meet your criteria. The size range looks to be about 3 or 4 to 1, and the spacings clearly differ by more than 5% as well.
I do. I think there's a relatively mundane explanation, but they're still weird.

And, after it came apart, SL9 continued on one more orbit before impacting Jupiter. That extra orbit allowed the pieces to separate far enough that, combined with Jupiter's rapid rate of rotation (once every 8 hours, if I remember correctly) the impacts of SL9 were spaced out.

What would happen if a comet made a close pass, started to break apart, and then slammed into a moon? I would expect to see a chain just like that shown in the APOD that was previously linked in this thread.

I certainly wouldn't immediately conclude that aliens broke a comet apart and then guided it to an impact. That is too silly even for good fiction.

Hello craterchains.

I suspected that you would get here eventually. I’ll begin with a caution that the guidelines within this forum are a bit tighter than at other fora, so please, let us focus on the positions held rather than the personalities involved.

Before proceeding any further, the posters interested in this subject may find your web site informative.

http://www.craterchains.com/

For clarity, I see a preponderance of evidence that this type of crater chain is the result of tidally disrupted objects. Probably Jupiter family comets which have passed within Jupiter’s roche limit and impacted Ganymede and Callisto on the outbound leg.

Given that you've been doing this investigation for three years, you should not be limited to the web-available subset. However, one-third of hundreds is still great. That's a fine subsamble. Let's see the data. I could use a table with planet, location (lat, lon, or perhaps an image catalog number), number of craters in the chain, diameter of each crater, and center to center distance of each crater. An image accompanying each would be best, but the lat lon will do so I could find them myself.

I need numbers, not anecdotes, so that table would be best.

I'd really like to see the images showing chains of 40 km craters. I'd be particularly interested in this subset. I'd be interested in how a chain of craters this large is identified.

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Why?

Why would there be much of a difference, whether the bolides hit simultaneously or not?

It sorta looks like something bouncing along the surface. Is that possible?

Milli360
Because of intrusion factor of one crater after the other. Both boundary walls and ejected materials falling back into the adjacent craters are protected during simultaneous impacts. One after the other would cause deformations in the adjacent craters.

As Heathen pointed out this has been discussed to some extent before on other forums. With some very interesting and varied results to say the least. This is the 4th open public forum that this is being presented at. Why am I doing this? Because after 3 years of investigations, the so called “probable” cause of something breaking up and making these types of crater chains seems even less likely than the first time I read that. My only hope is to jog some brains lose from the proverbial box and get them to thinking about just how slim of a chance that these kinds of crater chains could be caused by a natural event.

SL9 clearly showed that the size, trajectories of broken fragments, even speeds could at no time during its break up or path have caused any such chain of craters as we are questioning. I call that theory Bad Astronomy. How could anything neatly break apart in equally sized pieces then some how coalesce into such a near perfect string of impacts? What are the odds of that? Check the links from the APOD to find more pictures. Do some searches about crater chains.

Eye Zee
Yes, those numbers would be good to have. I would think some scientist, not some lay person like me, could do a kick *** grant proposal and get access to all available data and do it up right. Just the time that has been spent to date learning and investigating pales in comparison to what you ask for. Even with the limited resources we have come this far. It is time for others to investigate and research the true cause of these types of crater chains.
Were taped out with the available data we have in collecting the pictures. Not many come with captions that list all the particulars of the image.
Location;Jupiters moon, Callisto, north pole
Name;Gipul Catena
Length; 620 km
Average width; 40 km
Number of craters; ?
Date of photo; March, 1979
http://antwrp.gsfc.nasa.gov/apod/ap950715.html
http://www.lpi.usra.edu/research/outerp/cc2.gif

Location; Jupiters moon Callisto
Name; Gomul Catena
Length; 360 km
Average width; 25 km
Number of craters;
Splash Pattern? Possibly
Date of photo;
http://www.lpi.usra.edu/research/outerp/cc1.gif

Earthman2110
Possible, but not probable.

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It's not what you know or don't know, but what you know that isn't so that will hurt you. Will Rogers
http://www.craterchains.com/ns/nspage.html

Bring any useful science this time?...I'll take that as a no.

You need more if you want to convince a scientist: you need scientific evidence and scientific investigation (a viable theory). Not just your own intuition. Everything you say you think couldn't happen naturally has a reasonable scientific explanation.

It does not look like something bouncing along the surface.

Note that most of the craters have central peaks, also note that the craters are fairly circular. Neither of those would be expected if a single object had bounced or skipped across the surface of the moon.

You must have a different definition of "near perfect" than I do.

The crater diameters vary by at least a factor of 2 in the crater chains I saw in the links.

Apparently your aliens have weapons that shoot mishapen missles.

The chains you point to as anomalous look to me most like impacts along structural weaknesses (cracks in the Callisto ice, grooves on Phobos). Micrometeorites that would make smaller craters in stronger materials may excavate larger pits in the weak zones of these cracks and fissures. There is in fact no need for these chains to be formed simultaneously, and the diameter may be structurally controlled by the width of the fissure or groove. Given that you have a sample set of two for Callisto, and Phobos grooves and their associated morphologies have an abundant literature, the case is weak at best.

Frankly, this is a copout. The data is freely and publically available from the Planetary Data system. You don't need special permissions to access it. You also don't need a degree to collect the data I've described. Far from "paling by comparison," it would not take anything like three years for a lay-scientist to do a rigorous job using primary source data. The onus is on _you_ to take the research further rather than trying to pass the onus on to someone else.

If the callisto sample set of two taps you out, then it doesn't bode well for a more rigorous study, I suppose. Even those two images can be analysed in greater detail than what you present. In Gipul here is the results of literally five minutes of work with the linked gif image:
Approximately 13 craters - there may be one or two overlapping.
If we take the scale bar at face value 100 km, and assume a fllat projection, I get an average diameter of 34.1 km with a standard deviation of 4.7 km. greater than or +/- about 14%.
Center to center distance is averages 41.2 km +/- 8.8 or 21%.

Anomalously sized or distanced? I don't think so.

Imagine what even you could do with a better projection, a better scale bar, and _ten_ minutes of work...

__________________
“The simplest schoolboy is now familiar with truths for which Archimedes would have sacrificed his life.” – Earnest Renan

Enjoy counting, before they are wiped out by dust and wind.

Happy counting and dont forget to look closer.

__________________
It's not what you know or don't know, but what you know that isn't so that will hurt you. Will Rogers
http://www.craterchains.com/ns/nspage.html

less probable than little green aliens zapping holes in the moon?

the long link stinks... my page is all messed up now. and im still trying to figure out what exactly i am looking at, other than a bunch of pretty blue trapazoids... hmmm...

Craterchains, I'm not sure exactly how you've defined "uniformity", but it's obvious simply from looking at the photographs that none of the chains you've shown us so far have a range/median ratio, coefficient of variation, or anything else I can think of, which is anywhere near 5%, for either size or spacing. In case it's not obvious to you, take a look at Eye-Zee's calculations.

Even if you did present something, you'd then have to convince us that they're likely to be artificial, but I'm getting ahead of myself. There's no point trying to start a discussion about your findings based on data meeting this criterion when you won't show us said data. Let's see 'em.

Take a closer look.

Like the freakin link below.
Go Here
Sorry, tried it 3 different ways. Practice makes perfect, I'll try to get that worked out by the next post.

Hey Heathen, didn't anyone happen to think of the near zero gravity of Phobos for that little experiment? Read it, got a mild chuckle, it was an idea I'll grant them that.

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It's not what you know or don't know, but what you know that isn't so that will hurt you. Will Rogers
http://www.craterchains.com/ns/nspage.html

craterchains.

The majority of the chains on Mars are plainly secondary craters radial to much larger primary impacts. This mechanism is not to be confused with the catenae on Jupiter’s moons.

And if you want to jump to Phobos, add a third mechanism.

LINK

Craterchains, I have reproduced your link here in a much shorter format. Would it be at all possible for you to delete yours?

Condensed Link

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