[X] My Assistant

[djellison]

Look at the MI campaign on this puppy It's got to be a 4 x 4 frame MI mosaic

http://qt.exploratorium.edu:16080/mars/spi...cam/2005-04-28/

Doug

[helvick]

  Any impactor small enough to make a crater that small would certainly have burned up in the martian atmosphere. This is the sort of impact feature that may exist on the Moon, but never Mars.

That's true if the original object was small but largish meteors will break up and some small pieces will (occassionally) reach the ground - terminal velocity on Mars will be up to 500m/s for a small (5cm diameter) compact, roughly spherical and dense (iron).

Then there are secondary impacts from massive meteorite impacts elsewhere - the terminal velocity of a rocky secondary is probably a bit lower (300m/sec for the same dimensions) but even that has enough kinetic energy to make a neat round dent in something relatively soft which this looks like it might be.

[Guest_Sunspot_*]

There was some suggestion that meteorites impacting rocks at the Pathfinder landing site could produce small "craters" on them. Here's a story on the subject:

http://www.space.com/scienceastronomy/sola...mets990927.html

[JRehling]

I wonder how this rock picked up that tidy circular impression?

http://marsrovers.jpl.nasa.gov/gallery/all...I4P2564L7M1.JPG

There's always one good explanation for tidy circular impressions -- craters. In the absence of any other data, I'd guess it's a very small crater from a very small impactor.

I bet the rock is pretty soft or unconsolidated, though, to record a crater so nicely without being blown to bits by such an impact...

-the other Doug

Any impactor small enough to make a crater that small would certainly have burned up in the martian atmosphere. This is the sort of impact feature that may exist on the Moon, but never Mars.

They've found what look like tiny craters at Opportunity's site. Sure, if it's tiny when it enters the atmosphere, the object will disintegrate quickly. But if it's large enough, a small portion of it could make it to the surface.

I place my bet that it's simply a random formation - just like how we see shapes in the clouds, we happened upon a formation that has a round imprint on it.

If something large is worn down to something small, it won't be moving fast enough to create a "crater" when it hits. For example, the meteor spotted by Opportunity. If an object that size had hit the Moon, it would not be sitting there intact. By surviving entry, it is going too slow to vaporize the target area.

[dvandorn]

  If something large is worn down to something small, it won't be moving fast enough to create a "crater" when it hits. For example, the meteor spotted by Opportunity. If an object that size had hit the Moon, it would not be sitting there intact. By surviving entry, it is going too slow to vaporize the target area.

Meteors sometimes explode into fragments as they pass through an atmosphere -- even iron meteors. Especially if they enter at a highly oblique angle and experience a relatively long duration heating event.

If a meteor explodes, say, 500 meters above the surface and propels pieces in all directions, some few pieces will have their forward/downward motion greatly reduced,and will simply fall out of the sky from there. Falling from 500 meters, such a piece will hit and sit on the surface, just like we've seen at Meridiani. Happens all the time on Earth.

At the same time, a smaller chunk could be propelled from 500 meters on to the ground and make a tiny little crater. There would probably be a footprint whose far end would have a range of craters made by the chunks that survived and continued to the ground, and whose back end was made up of chunks of meteor sitting on the ground, relatively unscathed.

Yes, it probably happens pretty rarely that a chunk of meteor is slowed down by explosion dynamics and ends up sitting on the ground like it was set there by some giant's hand. But even things that happen *extremely* rarely can be commonly seen if you wait a few billion years...

-the other Doug

[dilo]

A couple of NavCam stitch mosaics from Sol473:


Regards.

[dilo]

Finally, Spirit found a chunk of blue Kryptonite levitating above a flat bedrock!...

[Guest_Sunspot_*]

Looks like they've driven round to the other side of Methuselah. Perhaps this was the site Steve Squyres was referring to in his update rather than Larrys Lookout visible in the distance.

http://qt.exploratorium.edu/mars/spirit/re...ACP1312R0M1.JPG

[stevo]

I'm curious about the "blue kryptonite". False color aside, its morphology is clearly different from the outcrop it's lying on (smoother for a start, implying newer? harder?) and it has odd swirly patterns on top. Can anyone suggest an origin? volcanic ejecta? meteorite fragment ?

And besides, if you look at earlier photos of the same rock, it appears to have a pretzel glued to one end ...

http://qt.exploratorium.edu/mars/spirit/pa...HEP2280L7M1.JPG

[dvandorn]

I'm curious about the "blue kryptonite".  False color aside, its morphology is clearly different from the outcrop it's lying on (smoother for a start, implying newer? harder?) and it has odd swirly patterns on top.  Can anyone suggest an origin? volcanic ejecta? meteorite fragment ?

And besides, if you look at earlier photos of the same rock, it appears to have a pretzel glued to one end ...

http://qt.exploratorium.edu/mars/spirit/pa...HEP2280L7M1.JPG

Without any APXS, Mossbauer or mini-TES data, just from looking at the rock, I'd guess it's a chunk of basalt that was dropped onto the hills from some nearby impact. It's more resistant to erosion than the softer rock that makes up the bedded unit of which Methuselah is an outcrop (thereby attaining the "perched" appearance after underlying rock has eroded out from under it).

Also, while I don't know what kind of false-color attributes this particular image has, similar false-color images out on the lava plains at Gusev have showed chunks of basalt highlighted in blue tones. So, if this image uses the same false-color assignations, I'd say the color suggests basalt.

-the other Doug

[dilo]

[Also, while I don't know what kind of false-color attributes this particular image has, similar false-color images out on the lava plains at Gusev have showed chunks of basalt highlighted in blue tones.  So, if this image uses the same false-color assignations, I'd say the color suggests basalt.

Doug, obviously image is not true colors, is an "extended" colors combination using L2+L4+L7 filters; no further manipulations, apart sharpening.

[dilo]

Amazing outcrops views on Sol477... Technically, a combination of 6 PanCam "pseudo-color" images (again L2+L4+L7 filters!) with little color manipulation in order to make it more "realistic".

The dark sand without any topography hint in the lower portion strongly recall me the first images from eagle crater...

[Hey, Tman, finally it seems I'm learning to correctltly use PTGui! ].

[Tman]

Amazing outcrops views on Sol477...  Technically, a combination of 6 PanCam "pseudo-color" images (again L2+L4+L7 filters!) with little color manipulation in order to make it more "realistic".

The dark sand without any topography hint in the lower portion strongly recall me the first images from eagle crater...

[Hey, Tman, finally it seems I'm learning to correctltly use PTGui!  ].

Hey Marco, it seems - immediately I excuse me for every request to help you!

Seriously, it's a very good and fine colored PTGui pan, compliment!
It makes hope to see more therefrom.

[ustrax]

Dilo...Have you seen the spidery looking rock on the top of the first hill counting from the left of the big chunk of rock on the right of the image?...
A Mars-barnacle?

[dilo]

Hey Marco, it seems - immediately I excuse me for every request to help you!

Seriously, it's a very good and fine colored PTGui pan, compliment!
It makes hope to see more therefrom.

Thanks Tman, but if I reached this result is also thanks to your suggestions!!!
(I obtained even more impressive results stitching my last holyday photos, PTgui is really powerful! - now I have only 5 more days trial period so I should spend EURO 49 to use it... )

[alan]

Larry, Curly and Moe
http://qt.exploratorium.edu/mars/spirit/pa...ACP2579L6M1.JPG