Excuse the jumping in here, but... Shelley, I'd say, is using "survive" in the sense of "outlive". So, the frown shows that the sculptor did a good job of reading the passions of Ozymandias. Thanks to the dead stones they're carved on, these passions outlive both the hand that 'mocked' (imitated) them (ie the sculptor) and the heart that fed them (ie Ozymandias himself).

As glennwsmith says, it's a good poem for Mars.

Getting closer...

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Wider angle view...

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This is probably a stupid question, but.....

Are meteorites on Mars actually interesting? I'm fully aware that BI may be a piece of deep ejecta, and appreciate why that would make it worth investigating, but the rovers have seen a couple well identified meteorites, and spent some considerable time going over them.

What can we learn from them that is different than what we would learn from meteorites on Earth?

CE

What's especially interesting is how many there seem to be. If this is typical, it suggests a rich area of future sampling opportunities during human Mars exploration missions, especially looking for very rare types. Comparing the range of types found on Mars with those found on Earth may be interesting too.

Phil

True, but in post 52 Tim Parker suggests that there are other reasons as well. We'll just have to wait and see.

(BTW, whenever I see or hear any reference to Ozymandias, all I can think of is Graham Chapman stumbling around drunk in Monty Python's Michael Ellis episode. A bit unfortunate...)

Other reasons we're going to the rock (other than it being big). Not that there are other reasons to go in that direction.

I suspect that each time a cobble is investigated it is hoped that it is not a meteorite but rather a rock from some distance away on Mars. Opportunity has studied hundreds of rather simillar local Meridiani rocks and so a rock from elsewhere on Mars is of great interest.

Such a rock is Bounce Rock which was found by Opportunity in April 2004. The rock was named for the fact that it was struck by Opportunity as the craft bounced to a stop during its landing stage. Bounce Rock bears a striking resemblance to a class of meteorites found on Earth known as shergottites, that are believed to have originated from Mars:

http://en.wikipedia.org/wiki/Bounce_Rock

I think that the Mars rock which would be of most interest would be another fragment of the formation of which the Antarctic meteorite AH84001 formed a part:

http://en.wikipedia.org/wiki/Allan_Hills_84001

The large meteorite which blasted AH84001 into space presumably blasted another million fragments of this formation into space. At least one of these fragments must currently be lying on the plain of Meridiani.

I understand that the most interesting meteorites of all would be fragments of the Earth close to 4 billion years old. Metamophism has severely altered all rocks of this age on Earth but it has been suggested that fresh fragments of Earth rocks of this age could be found on the Moon or Mars.

How can we be sure? Even if the ejecta from the AH84001 impact spread globally over Mars, what would be the surface number density of ejecta pieces large enough for Oppy to study, as a function of distance to the impact antipode?

The rocks did not become "well identified" until after going over them. An assumption that a rock is a meteorite before inspection could turn out to be wrong. More is learned about the geology of Mars if the rocks turn out to be Martian, but I guess the crater counters are interested in the number of surviving meteors on the surface.

It would be as interesting as Bounce rock: A piece of Mars from far away. I wonder if Opportunity would even be capable of detecting the carbonates in AH84001.

My vote for most interesting rock would be a chunk of limestone.

Astrophil, I think your reading is correct -- thanks!

Cryptoengineer, you make a good point re value of Block Island as a meteorite vs. piece of ejecta. But it's hard for us space junkies to ever think about a meteorite as anything but way cool -- even laying on the surface of Mars.

If ever you want proof of how cool a meteorite is, take a piece of Canyon Diablo (the meteorite that blasted out Meteor Crater) into a school classroom full of 6 year olds and let them hold it... "That's from space... it fell from the sky 50,000 years ago...!" Wow...! Then let them hold a piece (or in my case some VERY small pieces!) of a Mars meteorite... "... and that's from the planet Mars..." Cue eyes wide as saucers and a mouth formed into an amazed "o" shape...

Priceless...

nothing much happening .... so a super zoomed image of Block Island ...hyper processed
(zounds! the jpeg artifacts are awful!)

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oh well...

What a far-out thought! Those possibilities had not occurred to me, though they should have. Thanks for mentioning that, Paul. Do you have a reference to who first suggested it?

Given that any ejecta from an Earth impact would be going the wrong way in the gravitational well, what would be the probability that it could have the kick off velocity necessary to reach the orbit of Mars? And since Mars sweeps a greater orbit than Earth, wouldn't this further diminish the possibility of impact? Given the resouces available on site, how could we identify the provenance in any case?

The following is a study reported in 1989 which references previous studies.

Science News Mar 25, 1989
"According to S.A. Phinney... kicking a rock hard enough to free it from Earth's gravity would require a meteorite capable of making a crater more than 60 miles across. In addition, Mars' orbit is much larger than Earth's, so the chance of an Earth rock hitting Mars is about 10 percent that of the same thing in reverse....

...The group found fewer particles seemed likely to get to Mars than suggested by some previous analyses."

Looks like an iron meteorite. But a very intimidating one with a strange hole in one side. I hope it doesn't bite!
http://qt.exploratorium.edu/mars/opportuni...ARP0713L0M1.JPG

That is a big ass chunky lump of metal I think. It'd be worth a fortune if it was on Earth

Looks like the Beagle-2! *ducks and runs*

I don't think I would stake my paycheque, small as it may be, on that identification just yet.

A very incomplete color view of the meteorite


Look like they anticipated the shot after the move but the rock is not in the box. Or this is just a part of a mosaic.

The aspect of this rock looks very similar to Heatshield Rock.

The first article that I read which discussed the idea looking for Earth rocks on the Moon described the 2002 "Perspectives in Astrobiology" conference:

http://science.nasa.gov/headlines/y2002/18...s.htm?list82388

I remember first reading about extending the search for Earth rocks to Mars at around this time.

At the 2006 "Lunar and Planetary Science Conference" it was suggested that Earth rocks could have been flung as far away from Earth as Titan:

http://www.newscientist.com/article/dn8867...e-to-titan.html

A report on Block Island by the Mini-TES would be conclusive...
in the meantime...it looks like its either a dusty iron meteorite or coprolite

It would be astonishing - Mini-TES doesn't work anymore.

Glasses at the ready...

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Not too shabby, Stu! I like the little projection casting a shadow into the big pit.

Phil

looks like another iron meteorite similar to:

2004: "Bounce Rock"

2005: "Heat Shield Rock"

2006: "Allan Hills Rock"

...

------------------

“It's drive, drive, drive,” said Squyres.

Wouldn't a meteorite of that size make a crater?

It's just sitting there on top of the sand.

It could just be sitting here after coming from elsewhere; maybe it's a small piece of a larger meteorite that landed a few km away, scattering fragments over a wide area. It does look pretty beaten up.

Maybe the surface it landed on has ablated away, crater and all. How long do lumps of iron last on Mars?

Bounce was not an iron meteorite. It was ejecta from a Mars crater.

Nirgal - Bounce Rock resembles rocks found on Earth as meteorites, but on Mars it's an ejecta block. It's not made of iron.

Phil

What ngunn said: If it is an iron meteorite, the crater it made many millions of years ago would have long since eroded away leaving behind only the "indestructible" chunk of iron. If the impact was recent enough for the crater to still exist, the meteorite would be invisible, buried beneath the floor of the crater.

as far as cratering, I am sure the physicists and meteorite guys will weigh in , but we now have two pretty hefty meteorites (assuming that Block Island is one) that were found lying at the surface within 10 kilometers of each other and within the rover's vision... that is a significant observation.

as for the reasons....

angle of attack, speed, did it bounce or fragment? and the crater is covered over now...are any of the small craters in the near vicinity possibly related? Far away craters related? how long have they been sitting there? if you have 2 big meteorites every 10 sq miles, how many are lying on the surface of the planet? These few questions are from a multitude, that if answered well, will earn someone a PhD in Planetary Geology one fine day.

The crater no longer exists. If it did, the meteorite creating it would be buried beneath it.

Remember that a significant amount of material has been worn away from the surface that Opportunity is roving over. The layer of "blueberries" lying on the surface were eroded out of a layer of rock that is long gone. The crater was in that rock, or some other long gone layer.

The possibility exists of a history of ice coverage at Meridiani, where it is possible that any impact crater in that ice would have since sublimed away, leaving the meteorite intact.

I don't doubt that at all. I think meteorites are way cool. But I didn't see that we could learn much from a meteorite on Mars that we couldn't have learned from much-easier-to-study meteorites on Earth. There have been a couple interesting suggestions since I posted my question:

• They sample metoroids from a different part of the Solar System.
• They may preserve material from other bodies, such as the early Earth, the Moon (and presumably Io, etc).

Thanks for the responses. The photos I see of BI today really do look like an iron or stony-iron meteorite to my untrained eye.

CE

How big would be the crater caused by a pretty thing like Block Island?
Looking at the image at a first glance I had the impression of seing a circular pattern with what? help me here...70, 100mts? BI and bigger dunes stay in the center, I'm probably seing too much and this doesn't make any sense at all...
Here's what I mean, sorry but the only available tool is Paint...
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EDITED: I can distinguish it better in Tesheiner's map.

On this sandblasted plane Block Island is large enough to have caused local wind variations and isn't it possible that the larger ripples in the immediate area could be attributable to this rather than crater remnants? If BI is ejecta rather than an asteroidal meteorite then the impact could well have been at terminal velocity for Mars or less. No more than 1 km/s? That wouldn't punch a particularly large hole. We could even be looking at ejecta from Victoria. So even if it does have the composition of an iron meteorite, if it is a fragment spalled from the Victoria meteorite on impact it would again have hit at less than terminal velocity.

If it is a Victoria impactor fragment spalled on impact and ejected does that make it ejecta or meteorite?

My impression is that Victoria is too old for anything spalled from it's impactor to be lying on the current surface. Weren't we speculating a while back that Victoria* was formed before the hundreds of meters of sediment that Opportunity is traveling over were laid down?

*edit: Oops, getting my craters mixed up.. That was Endeavor. But the speculation on Victoria was that it was so old that it has been covered over and uncovered by deposition and erosion, still making it impossible that the current surface could be the surface on which part of it's impactor fell.

Actually, I think that's really the key concept to understanding the Meridiani meteorites. It doesn't seem like we see much exposed bedrock aside from regions near craters or between dunes. I get the impression that the environment is similar in one respect to Antarctica or glacier tops: the surface gets buried & exhumed periodically, and quite often what isn't sand or snow turns out to be meteoritic.

If this model's true, then these meteorites are probably all one-shot unrelated objects & not secondary artifacts of larger impacts.

And in line with the drift (pun intended) of Nprev and others, would it be correct to think that an iron meteorite is less likely to shatter on impact than a stony meteorite, and prove more resistant to a billion years or so of subsequent sandblasting?

The line of demarkation between impact ejecta and the pre existing sandstone is pretty clear at Victoria. In places the breccia is almost eroded away. So wouldn't the surface away fropm the annulus be pretty much at the level it was at the time of impact?

Of course. It seems likely that there would be more impact ejectites of Martian origin on earth than those of an earthly origin on Mars, but it is nice to know that some may be out there. For me, it is more exciting to think that our moon may be littered with early earthly ejecta, since that external body is so much more accessible to sample discovery and collection. On Mars, existing resources able to identify provenance are limited, but future instrumentation is in the pipeline.

Now, there's an interesting comparison, Tom.
How does the discovery rate of meteorites by the MERs compare with that of the Apollo moonwalkers?
Are there lessons here for learning, or is it "apples vs. oranges"?

Strictly speaking, our moon IS early earthly ejecta.

So far as I know none of the rocks collected by the Apollo astronauts have been identified as meteorites from elsewhere. However, this does not mean that every sample of lunar regolith has been examined for small fragments of exotic rocks.:

http://meteorites.wustl.edu/lunar/regolith_breccia.htm

I believe that many of the contributors to UMSF are geologists working for universities. Presumably NASA would respond favourably to those geologists if they requested a few ccs of lunar regolith to look for exotic rock fragments. Perhaps in the Apollo samples somewhere there is a tiny fragment of an Earth meteorite.

Perhaps a "moondust@home" web site could be set up along the lines of the "stardust@home" web site where members of the public could scrutinise a million fragments from the lunar regolith looking for something interesting.

EDIT: One implication of looking for fragments of Earth meteorites in samples of the lunar regolith is to prove that the Earth rock actually came from the Moon and did not represent contamination back on Earth. To overcome this problem the investigation would have to be done in clean room conditions.

(Admin edit. It's best to not cite this place as umsf dot com, as that's actually a functioning, different website that google will pick up on. Just UMSF - or the full URL, but don't turn the acronym into a URL)

Mars does of course have the advantage of an atmosphere, so hand-specimen sized meteorites can survive their arrival intact. Meteorites of any size hitting the moon are going to be mostly vaporized on impact.

John

Quick recap, comparison and celebration :-)

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