Mercury's Spider Crater (APOD 04 Feb 2008)

[Bad Buoys]

Yes, I was thinking subterranean explosions too; but a bit deeper than the one resulting in the crater you picture. I was more interested in those which were contained underground and which I saw slump and vent in peripheral whisps.

I can't find those tests or pictures right now as all I can find are our above ground tests [pictured by you] or their deep and fully contained tests. Very little chat of failures. What I did find is:

WHAT HAPPENS DURING AN UNDERGROUND NUCLEAR EXPLOSION
The detonation of a nuclear explosion underground creates phenomena that occur within the following time frames:

Microseconds
Within a microsecond (one-millionth of a second), the billions of atoms involved in a nuclear explosion release their energy. Pressures within the exploding nuclear weapon reach several million pounds per square inch; and temperatures are as high as 100 million degrees Centigrade. A strong shock wave is created by the explosion and moves outward from the point of detonation.

Milliseconds
Within tens of milliseconds (thousandths of a second), the metal canister and surrounding rock are vaporized, creating a bubble of high pressure steam and gas. A cavity is then formed both by the pressure of the gas bubble and by the explosive momentum imparted to the surrounding rock.

Tenths of a Second
As the cavity continues to expand, the internal pressure decreases. Within a few tenths of a second, the pressure has dropped to a level roughly comparable to the weight of the overlying rock. At this point, the cavity has reached its largest size and can no longer grow.6 Meanwhile, the shockwave created by the explosion has traveled outward from the cavity,
crushing and fracturing rock. Eventually, the shock wave weakens to the point where the rock is no longer crushed, but is merely compressed and then returns to its original state. This compression and relaxation phase becomes seismic waves that travel through the Earth in the same manner as seismic waves formed by an earthquake.

A Few Seconds
After a few seconds, the molten rock begins to collect and solidify in a puddle at the bottom of the cavity. Eventually, cooling causes the gas pressure within the cavity to decrease.

Minutes to Days
When the gas pressure in the cavity declines to the point where it is no longer able to support the overlying rock, the cavity may collapse. The collapse occurs as overlying rock breaks into rubble and falls into the cavity void. As the process continues, the void region moves upward as rubble falls downward. The “chimneying” continues until:
. the void volume within the chimney completely fills with loose rubble,
. the chimney reaches a level where the shape of the void region and the strength of the rock can support the overburden material. or
. the chimney reaches the surface.
If the chimney reaches the surface, the ground sinks forming a saucer-like subsidence crater. Cavity collapse and chimney formation typically occur
within a few hours of the detonation but sometimes take days or months.

This was part of a larger publication on the containment of nuclear tests at:
http://www.atomictraveler.com/UndergroundTestOTA.pdf

What I wonder is if this activity isn't at work with a lower yield and shallower. What would be the yield of an iron meteor which had been accelerating to the sun for years and now plows into Murcury's surface? What if underground ice were encountered accounting for faster braking and steam expansion?

[BMAONE23]

GO TO GOOGLE EARTH (great program) and enter "Yucca Flats" in the fly to locater box. The UG nuclear test site will load in your field of view. Looks like over 200 craters.

[Bad Buoys]

Yes, and this image also shows the pockmarked flat of the Yucca Mtn [whole region left of center]. Most of those were the result of bomb drops, devices on towers and those suspended from balloons. But what I search for is those few tests towards the end of the 50's where the research began to go underground. The first one, a night ignition, was described as a beautiful glowing blue Roman candle. Then they went deeper and decreased the yield such that they had what they consider their first contained underground blast in Sept 1957. So what I saw, a rapidly expanding, blurry [from dust or shock to the camera mount] dome which immediately collapses into a shallow crater with small venting plumes around the edge, must've been from this period as we shortly signed a treaty which allowed for no radioactive plume to cross international borders.

Craterchains, I see by your widest-angle picture that the slumping [?] we've been discussing in the NW quadrant is where the Spider Crater overlays a faint, smaller and much older crater.

Andy Wade, thank you very much for pointing me to Dr Wood. He is very knowledgeable and published on lunar, venetian, martian, and mercurian craters. But I was most stunned by the papers (A and B) regarding water based ice on Mercury's polar surfaces.

Addendum: The crater research is by Dr. Charles Wood, as AW said;
whereas the ice articles are contributed to by Dr Stephen Wood.

[henk21cm]

While researching CS types of crater chains for the past six years, CS means Concise and Systematic, FieryIce (Ms Gale Smart of BC Canada) and I have inadvertently become somewhat knowledgeable about craters and their formations.

Maybe you can enlighten the enigma for crater chains to us/me. As far as i (amateur) understand, a commonly accepted hypothesis is that a small object is 'ripped apart' by the gravitational field of a larger object. The successive impacts of tightly separated object, flying in formation, causes the crater chains. The splitting of Schoemaker Levy comet (early nineties) and the subsequental impact on Jupiter as an example.

From a conceptual point of view this may be the 'truth', yet does the physics and math of it end up OK? I've performed a 'Gedankenexperiment' and came up with some conclusions, which raised some questions about the 'ripping' hypothesis.

Assume a small object in the gravitational field of a larger object. Now slice the small object like a grapefruit into two halfs and separate these halfs over a small distance. The relative velocity of these halfs is zero, they follow their path at the same distance. The two small objects have a gravitational field of their own. The two halfs will exert a mutual gravitational pull on each other, which will eventually lead to the rejoining of the two halfs.

Now assume that half #2 of the small object is further way from the large object than half #1. (The plane of slicing is perpendicular to the distance vector between the small and large object). Since the gravitational field is decreasing when distance increases, half #2 feels a little less gravitational pull towards the large object than half #1. When the difference in gravitational pull towards the large object overcomes the mutual gravitational pull between the two halfs, the two halfs will split further.

Before doing some simple math we need two assumptions.
1) the distance between the centers of gravity of the two halfs is approximatedly the radius of the original (unsliced) small object
2) the volumetric density of the large and small object are of the same order of maginitude (the scale depends on the qubic root of the ratio of the two volumetric densities)
The result is that the difference in gravitational pull towards the larger object will overcome the gravitational pull between both halfs, if the small object is rather close to the large object: about the diameter (twice the radius) of the large object.

Since Mercury is much further away than 1.5E6 km from the sun, the gravitational field of the sun can not be the culprit for any crater chains on Mercury. The diameter of Mercury itself, approx. 4E3 km, makes the time for splitting up a comet into several parts rather short, of the order of a quarter of an hour (flying a 4 km/s). So i have some doubts.

Allthough cohesion in the small object is expected to be very small, it will hamper the splitting up of the small body. This adds up to my doubts.

Maybe someone can enlighten this enigma for us/me, or proove my assumptions, math or physics to be wrong.

Regards,
Henk

[craterchains]

Bad Buoys,
I doubt anything is going to slow down such a meteor headed into Mercury, at least to any measurable degree. Yes, there could be water ice near the poles on Mercury.
FieryIce found this image for you. What a way to make deep underground caverns. And with modern thermonuclear devices they lose their radioactivity very fast.
http://www.wipp.energy.gov/science/UG_L ... /gnome.htm

Henk,
What you are calling an "enigma" is also referred to as an "anomaly" that remains when doing the math on a "rubble pile" comet possibly causing these CS types of crater chains. Many scientists actually agree that it "just isn't possible", and their computer models say the same. The models just don't show it is possible. Your math is accurate and matches up with renowned scientists that have also done the math. "Carefully" read their papers and you will find this out.

The anomaly remains, the enigma continues, broken up space rocks didn't make these CS types of crater chains, , , , , so what did? The answer we propose "nobody" wants to talk about, or even consider. Not to mention the fact that there have been attacks on anyone wanting to discuss such possibilities of a war in our solar system. Go figure.

Norval

[henk21cm]

The anomaly remains, the enigma continues, broken up space rocks didn't make these CS types of crater chains, , , , , so what did? The answer we propose "nobody" wants to talk about, or even consider.

Norval,

Thanks, your comment would have made my math teacher (+-1965) proud.

Breaking up a pile of rubble may be caused by some kind of internal (outwardly directed) pressure. Since heat conductivity of a pile of rubble is rather poor, the effect of heating up the comet by solar radiation may trigger some chips at the surface to be blown away, but splitting a pile of rubble into large chunks, is not likely. If the source of the pressure is water, the ice must be'boiling'. Gasses like nitrogen (77K), oxygen (90K) are not that abundant to be a candidate for the pressure. Methane maybe, ?130K?.

Anymore processes which may cause the breaking up?

Regards,

[craterchains]

Henk,
As far as how to break up a comet / asteroid goes, disruption by gravity seems to be the answer, and is acceptable to me.

As for them making such concise and systematic chains of craters as in CS types of crater chains, well it just ain't going to happen.

The anomaly remains of what made them still, if one does not accept other intelligent life may have caused them.

It is reputed that some of the aliens produce allot of "gas" (methane), or in other words, for gawds sake, don't light a match!

One should still maintain a sense of humor, even when confronted with the probability of a war in our solar system having happened.

[Bad Buoys]

If I'd like to stop by for some stimulating conversation, there aren't too many homes in the Tacoma area with foil covered windows, are there?

I would hope you'd leave your irrational and unsubstantiated theories behind. But if you truly believe that some advanced civilization can travel to our area yet still wastes their time and resources in the destruction of life and property; and with low tech methods of throwing things at each other and yet their technology is not so good that they don't miss and thus leave your crater remnants - but no evidence...maybe you're too far gone. Though you've attributed similar activity to them as we've displayed worldwide it's remarkable that they're able to travel about our solar system without detecting us; or if they did, they were able to refrain from subjugating us, unlike ourselves.

But I'm still curious as to the crater. Is the lack of a cliff wall in the NW quadrant because of a slight angle to entry path, slumping of the wall, or some factor related to the underlying, smaller, older crater which intersects at just that point?

Also, if troughs what forms them? Is it usually rolling debris or liquid. If as young as this crater appears, what could such a liquid be? Have any methods been developed to date craters?

[craterchains]