Mercury's Spider Crater (APOD 04 Feb 2008)

Bad Buoys · Post by **Bad Buoys** » Mon Feb 04, 2008 6:13 am

With the sunshine coming from the lower right of the photo, my mind is having a hard time assembling what must be a very steep and deep cliff down to the depression in the center from which all the rays seem to eminate.

I'm hoping Crater Chains will give us his insight.

neufer · Post by **neufer** » Mon Feb 04, 2008 11:01 am

Stowaway by Richard Edwards

Tarantula, tarantula,
Hidden in your crate,
Can you feel your hunger
Turning into hate?

Tarantula, tarantula,
Being swung ashore,
What are all those whiskers
And those fine fangs for?

Tarantula, tarantula,
Lowered to the quay,
Will you thank the greengrocer
When he sets you free?,

Tarantula, tarantula,
Scuttling out of sight,
Whose bed will your darkness
Glide beneath tonight?

g-banjo · Post by **g-banjo** » Mon Feb 04, 2008 11:16 am

Can anyone tell me why this photo has been inverted?
The image is much clearer if you download and use photoshop (or whatever) to invert the colour back to the way it should be.

Case · Post by **Case** » Mon Feb 04, 2008 11:24 am

The full res image seems quite blurry. Would that be motion blur from the high speed flyby?

zorro · Post by **zorro** » Mon Feb 04, 2008 12:15 pm

I agree with g-banjo. I wondered why they were calling them troughs until I inverted it.

NoelC · Post by **NoelC** » Mon Feb 04, 2008 12:41 pm

It's quite obviously not inverted. As Bad Buoys put it, the sun is coming from the lower-right. Rotate the image 180 degrees (i.e., turn it upside down) if your mind can visualize the surface better with the light coming from the upper-left.

-Noel

dduggan47 · Post by **dduggan47** » Mon Feb 04, 2008 1:11 pm

zorro wrote:I agree with g-banjo. I wondered why they were calling them troughs until I inverted it.

If the troughs look like ridges ... keep looking. It's an optical illusion. When I first saw it I thought it looked like a big rock in the middle with the sun coming from the upper left. It took a while to get it right.

zorro · Post by **zorro** » Mon Feb 04, 2008 1:29 pm

OK, now I agree with NoelC. So my question is, why not rotate the picture on APOD for the benefit of the clueless?

orin stepanek · Post by **orin stepanek** » Mon Feb 04, 2008 1:29 pm

http://apod.nasa.gov/apod/ap080204.html

Looks like a splash effect when it hit.

Orin

dduggan47 · Post by **dduggan47** » Mon Feb 04, 2008 1:49 pm

What puzzles my little non-scientific mind is that the "lines" don't emanate from the center of the crater. In some cases they don't seem to come from the crater at all. One or two appear to run right by the crater.

Also, many are not straight.

Edit: One more thing, there seems to be a fair amount of discontinuity where the two pictures are pieced together. Is that just a difference in focus?

g-banjo · Post by **g-banjo** » Mon Feb 04, 2008 2:04 pm

Yep, I see it now, not inverted at all.
Could this be the result of two impacts with the second filling in the crater of the first? There seems to be two centres to the rays.

trafkat · Post by **trafkat** » Mon Feb 04, 2008 3:15 pm

These two craters don't appear related. The older (and somewhat larger) appears to be the source of the rays. I suppose that the older one is volcanic in origin, or that a partially liquid obeject struck the surface, or the surface
was somewhat liquid at the time of impact. The
newer one seems to be an impact crater but I know it's hard to distinguish between the two
kinds for my un-expert eye.
It's a shame that many observers don't seem to
recognize two craters.

emc · Post by **emc** » Mon Feb 04, 2008 3:57 pm

Are the lines telling us anything about density? Kinda looks like placing a heavy object on a blanket covering a mattress.

FreebirdsWB · Post by **FreebirdsWB** » Mon Feb 04, 2008 4:13 pm

Strange indeed. It took me a long time looking to see the crater as a crater and not a mesa. Then, I could see the rays as canyons and not ridges.

So we have a series of canyons leading to a double impact site... one significantly older than the newest. And, to me, it sure looks like the older is the cause of the rays.

So what caused the canyons? Did the original impact crack the surface like an eggshell? Surely it isn't suggestive of liquid erosion on Mercury (although the old impact site does remind me of the lunar "seas".

Looking forward to the professional opinions...

Bruce D. Dod · Post by **Bruce D. Dod** » Mon Feb 04, 2008 4:58 pm

I notice an interesting fault line going from the 9-o'clock to the 1-o'clock position on the photo. There is considerable offset between the upper block (shift left) relative to the lower one. When one re-aligns the blocks, an interesting pattern to the radials appears.

g-banjo · Post by **g-banjo** » Mon Feb 04, 2008 5:06 pm

I think you'll find that's a join between two photos.

Bruce D. Dod · Post by **Bruce D. Dod** » Mon Feb 04, 2008 5:17 pm

a "photo joint" perhaps, but terribly offset. Some of those "rays" will point to the crater better when realigned.

neufer · Post by **neufer** » Mon Feb 04, 2008 7:16 pm

orin stepanek wrote:http://apod.nasa.gov/apod/ap080204.html

Looks like a splash effect when it hit.

Orin

Maybe it: "Looks like a splash effect when THEY hit."

When a [Shoemaker-Levy 9 type] broken comet hits
a rotating moon/planet one gets this effect:
.
http://antwrp.gsfc.nasa.gov/apod/ap011215.html
.
But what happens when a [Shoemaker-Levy 9 type]
broken comet hits a planet that barely rotates at all?

Splosh...splosh...splosh...splosh...

Andy Wade · Post by **Andy Wade** » Mon Feb 04, 2008 7:46 pm

g-banjo wrote:Yep, I see it now, not inverted at all.
Could this be the result of two impacts with the second filling in the crater of the first? There seems to be two centres to the rays.

Is there any evidence of volcanic activity on Mercury?
I was wondering if this was originally a volcano that received a direct hit causing the crater we see now. Also, there is a large amount of discolouration.

shovelhead · Post by **shovelhead** » Mon Feb 04, 2008 8:21 pm

I think the older and much larger first crater formed by an impact had left a depression that filled up with liquid.When the second impact hit it splashed the liquid. The splashed liquid that went higher above the surface of mercury gelled before landing which caused the ununiformed ridges.Also I think the first impact made the horizontal fault line.

g-banjo · Post by **g-banjo** » Mon Feb 04, 2008 8:43 pm

I don't see a horizontal fault line.

Arramon · Post by **Arramon** » Mon Feb 04, 2008 8:47 pm

d'oh! what fault line?? the line is the seam between both photos.

The many smaller, fainter lines radiate from an older, larger area beneath the newer crater. The fewer, deeper ridges come from the newer crater impact, as if material (molten whatever) was released, cutting those few deeper ridges and flowing out of the seen picture, as the flow cut through older channels previously carved out during the older impact below. The coloration of the entire area is more than likely from the fallout of the newer impact.

=/ interesting...

g-banjo · Post by **g-banjo** » Mon Feb 04, 2008 8:57 pm

I'd say that's about it indeed.

henk21cm · Post by **henk21cm** » Mon Feb 04, 2008 10:05 pm

[quote="g-banjo"]I don't see a horizontal fault line.[/quote]

Basically parallel to the seam in the two pictures.

I was puzzled a bit, but did you notice that all craters are imposed onto the rays? Without more detail i can not find any craters which are overlayed by any rays. IMHO the rays are an old terrain feature. The central crater is accidentally near the centre of the caldeira and its rays. Like others have put forward: the alignment between crater and rays is not perfect. Maybe a diameter of the crater to the top of the picture.

Astonishing picture, might i say.

J. Everett · Post by **J. Everett** » Mon Feb 04, 2008 10:10 pm

Perhaps not a crater at all. Rather a plug.

Starship Asterisk*

Mercury's Spider Crater (APOD 04 Feb 2008)

Mercury's Spider Crater (APOD 04 Feb 2008)

Tarantula, tarantula, Hidden in your crate,

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