Opportunity Mission 2009 and onward

[JonClarke]

That certainly looks like a meteorite.

Jon

 

[MeteorWayne]

Me too! WOuldn't have wanted to be under that when it hit! It probably weighs several hundred kg.

 

[3488]

That certainly looks like a meteorite.

Jon

Me too! WOuldn't have wanted to be under that when it hit! It probably weighs several hundred kg.

Hi Jon & Wayne,

Yes I agree, this is most definitely a meteorite, a large one too.

It is approx 60 CM wide, so yes that is a heavy lump of asteroidal iron. Opportunity has really got into heavy metal (not Iron Maiden, Black Sabbath, AC/DC type :mrgreen: :mrgreen: ), since the first meteorite back in January 2005, Heat Shield Rock.

I find this sort of thing fascinating. I assume the iron meteorites discovered by both Spirit & Opportunity on Mars are from the same source as those found on Earth?

Perhaps from Main Belt asteroids like 16 Psyche or 21 Lutetia (21 Lutetia a large hybrid Silicate / Metallic asteroid which the ESA Rosetta Spacecraft will closely encounter next July, very exciting).

Front HazCam view of Block Island Meteorite. Sol 1,960.

IDD being dployed onto Block Island Meteorite. Sol 1,960. Hope we get to see the MI images soon.

Another image here just returned Sol 1,961.

Andrew Brown.

 

[3488]

Sol 1,961.

Microscopic Imager images of the Block Island meteorite.

As can be seen by the CCD Blooming, this meteorite is certainly metallic, almost certainly iron.

Andrew Brown.

 

[JonClarke]

One side looks rounded, the other very rough. Did it break up in mid air, or on impact? Or this this flight asymmetry?

The ease wih which meteroites are being found on Mars in the right terrain is interesting. A few years ago I was involved with a study of a Mars polar station, part of the scientific rationale was that Mars would "sample" a different meteroiet population to earth and so meteorite classes rare on earth might be common there and there may be whole new categories present. Not that you would send a mission to Mars just for meteorites, but if you were theye you would certainly study them. From the Opportunity experience you would not need to go to the poles.

Jon

 

[MeteorWayne]

It kind of makes sense, Jon. The two places on earth where the most meteorites are found are Antarctic ice and deserts. One reason is that they are so different than the surrounding material.

Also in Antarctica, they are concentrated by flowing ice.

In deserts, the extreme dryness reduces the rate of erosion, which is primarily due to aeolian processes, which degrade the meteorite much more slowly than water weathering, particularly for irons.

Pretty much the entire surface of Mars is comparable to earth's deserts, if a bit cooler

Wayne

 

[3488]

One side looks rounded, the other very rough. Did it break up in mid air, or on impact? Or this this flight asymmetry?

The ease wih which meteroites are being found on Mars in the right terrain is interesting. A few years ago I was involved with a study of a Mars polar station, part of the scientific rationale was that Mars would "sample" a different meteroiet population to earth and so meteorite classes rare on earth might be common there and there may be whole new categories present. Not that you would send a mission to Mars just for meteorites, but if you were theye you would certainly study them. From the Opportunity experience you would not need to go to the poles.

Jon

That's a very interesting point Jon, if there are whole different types of meteorites on Mars than on Earth. The one Oppy is currently analysing, certainly looks like an iron meteorite. Will be interesting when the APXS & Mossbauer (I assume the Mossbauer is still working) data is returned. Obviously the RAT cannot be used on it as it is far too hord & will quickly render the RAT useless. Spirit's got worn down by the hard volcanic basalts in Gusev crater, but this would be even harder.

Wayne would know more than me about the atmospheric entry & impact dynamics. If it was spherical & somehow split in half, the other half should be lying around somewhere.

With Mars's extremely thin atmosphere, I would assume that bollides impacting the martian surface would be far less effected by ablation than those impacting Earth (though Mars landers still need heat shields)? After all the martian atmosphere typically at the surface is approx the same density as Earth's is at approx 30 KM or 19 miles above sea level.

Also I wonder if it would be possible to determine how long the Block Island meteorite has been there? Recently within the past few million years, or before the Dinosaurs, or before multicellular life on Earth????? It would be interesting to find out. My guess is that it was after Meridiani dried out, seeing as there appear to be no 'splash marks' or deformation, etc on the ground around Block Island.

Sol 1,963 MI image of Block Island meteorite.

Sol 1,963 image of Block Island meteorite.

Sol 1,963. Front HazCam, showing Opportunity analysing the Block Island meteorite.

Andrew Brown.

 

[MarkStanaway]

Awesome photos!!
I too am amazed at how easily they seem to be finding meteorites lying around on the surface. Just stumbling across one on its traverse to Endeavour crater seems to indicate that there must be quite a few just lying around on the surface in this vicinity.
That sand that is sitting in the basin part of 'Block Island' could indicate that it has been recently exposed after being buried. It would depend weather it is compacted or loose. If loose it may have been deposited as the result of a recent dust storm.
Mark

 

[MeteorWayne]

LOL, well it's not exactly like there are lots of meteorites laying around on the surface....so far there have been exactly 2 AFAIK.

First, some background from the SDC article by Andrea Thompson:

"
Opportunity's handlers spotted the rock, which measures about 2 feet (0.6 meters) across, in images sent by the rover on July 18 in the opposite direction from which the rover was driving. The rock, dubbed "Block Island," is unusual for its size, mission scientists said.
{snip}
Mission managers decided the rock was worth a closer look and had the rover then backtrack some 820 feet (250 meters).

Over the weekend, scientists used the rover's alpha particle X-ray spectrometer to get composition measurements and to confirm it was a meteorite.

"It's pretty clear now that it is," Yen told SPACE.com.

The rock has a similar composition to another meteorite that Opportunity found in Jan. 2005. That meteorite was the first to be found on another planet. It was lying just over half a mile from its landing site in Mars' Meridiani Planum. Since landing on Mars in 2004, Opportunity has driven across 10.7 miles (17.2 km) of the red planet's surface.

The 1-foot (31-cm) diameter slug of iron and nickel gained the moniker "Heat-Shield Rock" due to the rover's discarded heat shield having come to rest only 20 feet (6 meters) from the meteorite.

There are some differences between the two meteorites though and scientists plan to use some of Opportunity's other instruments to learn more about Block Island.

{snip}

The rover team has also taken color and microscopic images of the meteorite. Next up are measurements with the rover's Mössbauer spectrometer, which can tell scientists more about the mineralogy of the rock.""

So in about 11 miles (17 km) or driving across a desert, we have found 2 iron meteorites.

Meteorites are much more likely to survive intact to the Martian surface due to factors that Andrew pointed out, much lower atmospheric density, and a much lower impact velocity with the atmosphere...I'll discuss those in more detail in my next post.
Also, here on earth, those pesky humans tend to remove such unusual rocks when they spot them; and even in deserts, due to the humidity and rainfall (yes, even deserts get rain) the meteorites (especially irons) rust away over geological time.

So if there was no life on earth and no water, 2 such meteorites in 17 km might not be an unreasonable density.

On to the next post for velocity details.

 

[MeteorWayne]

OK, part deux:

Andrew asked a couple of good questions that made me get out my Jean Meeus, calculator, and a number of other reference books.

For any planetary body, the impact velocity is the square root of the (sum of the escape velocity of the planet squared (minimum speed) plus the heliocentric velocity of the impactor squared).

For Earth, that means the minimum speed is 11.2 km/sec, or ~25,050 mph.

For Mars, it's 5.03 km/s, or 11,250 mph. That's a LOT slower.

The maximum possible impact speed for an object in orbit around the sun is the scenario where an asteroid or comet is in a highly elliptical retrograde orbit around the sun and hits the planet head on going in the opposite direction. These would be much more likely to be comets, or meteoroids derived from comets, since that is the only population of solar system objects that are in retrograde orbits in significant numbers. The speed before the gravity adds in is then the sum of the planet's motion around the sun, and that of the impactor. This gives us meteor showers (not meteorites) like the Leonids, and the 2 showers from Halley's comet, the Orionids, and eta Aquariids. That maximum speed for the earth is about 72 km/sec, or ~ 161,000 mph. (~ 30 km/sec earth orbit, ~ 41 km/sec for the object, plus gravitational acceleration.)

Mars has a more elliptical orbit, so I had to actually calculate the values for aphelion and perihelion. This changes both the orbital velocity of Mars, and the maximum speed of the impactor. Of course, Martian gravity doesn't change.

At Aphelion, Mars moves ~22 km/sec, + Impactor max 32.6 km/sec + gravity results in 54.6 km/sec or ~122,140 mph.

At Martian perihelion, the planet moves ~ 26.3 km/sec, the impactor max speed is 35.8 km/sec, + gravity = 62.1 km/sec or ~ 138,900 mph.

So those are the max in minimum impact speeds. Minimum is 5.03 km/s, or 11,250 mph (compared to 11.2 km/sec, or ~25,050 mph for Earth)

The max speed at perihelion is 62.1 km/sec or ~ 138,900 mph for Mars (compared to72 km/sec, or ~ 161,000 mph for earth).

Next post will discuss some realistic scenarions, since these speeds are just the boundaries, not most likely.

 

[MeteorWayne]

OK, now we can make some simplifying assumptions.

First, we can assume that most meteorites would come from the asteroid belt. Any from other parts of the solar system would be extremely rare.

This implies a few things. First, that the objects would be in a prograde orbit, so Mars' orbit velocity would be subtraced from the appoach speed. Over 99.9% of asteroids are in prograde orbits.

Second, that since they come (or came) from the asteroid belt, at MOST the "a" (semimajor axis) would be 4.5 AU....3 AU would be more likely, but I'm working with highest possible velocities to give plenty of wiggle room.

Just to get ballpark figures here, I'm using the average orbital velocity of Mars combined with a prograde asteroid from the Main Belt. This results in an approach speed to Mars of ~ 7 km/sec. Combined with Mars' gravity, this results in an impact speed of ~ 8.7 km/sec, which is only ~ 19,500 mph. This is less than the minimum speed that any meteoroid can hit the earth's atmosphere.

So what we can say here is that while the mini asteroid that produces a meteorite of the surface will be heated enough to be somewhat ablated, with the thin atmosphere, it would be quite unlikely that dynamic pressure would reach levels high enough to shatter the objects, particularly for iron meteoroids. Chondrites might shatter very close to the surface.... I still have to do some more calculations.

It would therefore seem that irons will arrive on the Martian surface almost intact, with a slightly melted surface, and a velocity from 3-5 km, sec... fast enough to not want to be under it, but not paticulary high by earth standards.

I should point out that these assumptions do not apply to the large crater creating impacts, which probably come from further out in the solar system and were more massive. Particularly during the Great Bombardment about 3.7 GY ago, those objects would have had much higher impact speeds, and obviously were more massive. Here I am speaking just about meteorites that would be found on the surface from the last billion years or so, which most likely came from the asteroid main belt.

Hope you all enjoyed this exercise....it was good since I'll have all these facts on hand for my astronomy class next week which is about comets, asteroids, meteor showers, and meteorites .

Wayne

 

[3488]

Thank you very much Wayne on your hugely informative posts.

It is interesting to see that the impact sppeds are less than for Earth due to the fact, that difference in speed betwwen Mars & the potential source of impactors from the Asteroid Belt will be less than it would be for Earth. That makes sense as both are further from the Sun than Earth.

I did think that Mars's lesser gravity would also contribute to lower impact speeds than for Earth. I did think correctly that the thin martian atmosphere would have a lesser effect of the bollide.

As Jon said in a slightly earlier post, it would make for a fascinating side mission for future landers & rovers to analyse any meteorites found on the martian surface & see how these compare to what impacts Earth also it is a back door approach to studying asteroid belt material.

I think this diversion to Block Island is most definately worth it. Also it is great to read from Wayne's update that Opportunity has confirmed that Block island is indeed a meteorite. Myself I had no doubt what so ever, a metallic, pitted boulder, that looks like a meteorite, on the surface of Meridiani Planum, clearly something that is out of place.

Sol 1,964 Microscopic Images of Block Island metoerite. looks like the MI is doing a mosaic??? If so, it will be very interesting. Mind you, each image covers an area only 3.1 CM on each side

Andrew Brown.

 

[3488]

Sol 1,965 Microscopic imager images of Block Island meteorite.

Andrew Brown.

 

[MeteorWayne]

This ought to make some mosaic when they are done!

 

[3488]

This ought to make some mosaic when they are done!

It certainly will be Wayne. To me it definitely looks like a mosaic is being composed.

I wonder if they will do the whole of Block Island or if that will take too long? I would imagingf mission controllers will want to start heading towards Endeavour Crater before too long. Mind you, Oppy is in great shape, power margins are excellent, so I suppose there is no urgency.

Myself I think this is a wonderful diversion, closely examining material from the Asteroid Belt on Mars. Not too long ago, this would have been science fiction, but we are now actually seeing it for real.

Not only that Black Island has so much to reveal, not only about asteroidal iron, but also perhaps about the conditions on Mars it's endured since impact. Maybe even clues as to how long it's been there based on information gleaned from Oppy on Meridiani Planum since landing successfully in January 2004. This is real planetary science, though neither MERs have ever been used friviously anyway.

Block Island Meteorite Sol 1,965.

Andrew Brown.

 

[MeteorWayne]

Realistically, and I hate to make a bad pun (In truth, I don't; I'm a very punny guy), since both rovers have outlived their design lives by ~ 25 times, targets of "opportunity" is what they should be doing. There's no guarantee Oppy will make it to Endeavour, so when something so unique drops into your lap (or sandy suface as the case may be) you need to take advantage of it. At this point, there's no way to speculate what might be learned with the "free science" And there's no way to know when the end will come. This is much like human geologists would act. Sure you have plans, but when presented with something really special, you stop and investigate before you move on with the plan.

 

[3488]

Too true Wayne,

I am very glad that mssion planners have used the 'opportunity' with Opportunity (pretty rubbish was'nt it) to examine Block Island. This really is a chance far too good to miss.

I still think Oppy will get to Endeavour Crater, though of course chance would not favour it due to Oppy's eceptionally long life on Mars, but when you're 25 times over your 'life expectancy' than yes, you grap every opportunity of added interest you can, of which thias most certainly is (did it again).

Andrew Brown.

 

[MeteorWayne]

Some followup info on Martian Meteorites:

This does not include the latest find, but provides good info on the previous ones

http://www.psrd.hawaii.edu/May08/MetsOnMars.html

Excerpts:

Regarding Oppy's first Iron:
"As summarized by Schröder and colleagues, spectra obtained by the Mini-TES of the rock showed features akin to the Martian atmosphere, which meant it was highly reflective at mid-infrared wavelengths, a characteristic of metals. This led to the logical thought that the rock was an iron meteorite. Further classification of the meteorite was allowed by the onboard instruments: APXS, Mössbauer, MI, and the RAT.


•Alpha Particle X-ray Spectrometer - The APXS-derived bulk elemental composition of Meridiani Planum meteorite is 93% iron, 7% nickel, ~300 ppm germanium, and <100 ppm gallium.

•Mössbauer Spectrometer - Spectra from the RAT-brushed surface show 94% of the iron is in a metal phase. On the basis of the iron/nickel ratio, this phase was assigned to kamacite (an iron-nickel mineral with low nickel content). Mössbauer spectra of both the "as is" and the RAT-brushed surface show ~5% of the iron is in the ferric state (Fe3+). Schröder and colleagues suggest some of the iron may have been oxidized during the meteorite's fall through the Martian atmosphere.
This meteorite was officially approved on October 10, 2005 with the name "Meridiani Planum" and remains the only approved meteorite on Mars. It is classified as a IAB complex iron meteorite. "

The second possible:

"The second rock proposed by the MER Opportunity team to be a meteorite is a 3 centimeter-sized pebble at the rim of Endurance crater and unofficially named Barberton. It was found on sulfate-rich bedrock in the midst of basaltic soil and a hematite spherule lag deposit ...


Schröder and colleagues report Barberton was analyzed with the Microscopic Imager, the APXS, and the Mössbauer Spectrometer, but it was too small to be brushed or abraded with the RAT. Some of the surrounding soil was also analyzed for comparison. Barberton is olivine-rich and contains metallic iron in the form of kamacite, suggesting a meteoritic origin. However, Schröder and coauthors also report that although it is unique among samples investigated at Meridiani Planum, Barbarton's high magnesium and nickel contents and low aluminum and calcium contents would also be consistent with an ultramafic rock of Martian origin. Though it cannot yet be proven that Barberton is a meteorite, if true, then cosmochemists say it is similar in Mg/Si, Ca/Si, and Al/Si ratios to howardites and diogenites (rocks formed from basaltic magmas), but enriched in S/Si, Fe/Si, and Ni. The authors suggest Barberton, then, is chemically most consistent with a mesosiderite silicate clast with some additional metal and sulfide"

The 3rd:

"A 14-centimeter long cobble, dubbed Santa Catarina, is the third possible meteorite found by the Opportunity rover team. Schröder and colleagues describe Santa Catarina as a fractured, brecciated rock containing some clasts with possible igneous quench textures in olivine minerals (see images below). The cobble could not be abraded or brushed because of its geometry, but it was analyzed with the instrument suite of Microscopic Imager, APXS, and Mössbauer Spectrometer. Santa Catarina has an ultramafic composition with unusually high nickel. Schröder and team say that compared to other materials analyzed in Meridiani Planum, Santa Catarina is most similar to Barberton. Element ratios of Mg/Si, Ca/Si, Al/Si, S/Si, and Fe/Si are all very close to soil-corrected values obtained for Barberton. According to the authors, the iron-bearing mineralogy is, as in Barberton, dominated by Fe2+ in the minerals olivine (52%) and pyroxene (26%). Santa Catarina is more oxidized than Barberton with 14% of the iron as nanophase ferric oxide--a weathering product. Schröder and colleagues identified 7% troilite (iron sulfide) in the Mössbauer spectrum, but no kamacite (as had been found in Barberton or Meridiani Planum meteorite)"

# 4&5 (possible)

"The fourth and fifth possible iron meteorites were identified based on MER Spirit's remote sensing instruments in the Columbia Hills inside Gusev Crater. They are 25- to 30-centimeter boulders, named Zhong Shan and Allan Hills (see image below). Schröder and colleagues show the Mini-TES thermal infrared characteristics of these possible meteorites are similar to the Meridiani Planum meteorite (see diagram below). All three rocks display spectral characteristics similar to the Martian atmosphere because metallic iron is highly reflective in thermal infrared (as well as visible) wavelengths. But because these rocks lie on steep terrain and were discovered after the failure of Spirit's right front wheel, detailed investigations with the rover's Microscopic Imager, APXS, and Mössbauer Spectrometer were not possible"

See the link above for more text and the images of the previous meteorites...

Wayne

 

[MarkStanaway]

Darn it!!
Here was I thinking how remarkably similar to a gold nugget these meteorites look.
To think of the possibilities if only that were true!!!
lol
Mark

 

[centsworth_II]

....To think of the possibilities if only that were true!!!

Not so fast :lol:

At 1000 dollars an ounce, a 1000 pound gold nugget would be worth 16 million dollars. The Mars Science Laboratory, Curiosity, will cost over TWO BILLION dollars (125 times the value of the nugget), and all it could do is go LOOK at that nugget.

 

[JonClarke]

Realistically, and I hate to make a bad pun (In truth, I don't; I'm a very punny guy), since both rovers have outlived their design lives by ~ 25 times, targets of "opportunity" is what they should be doing. There's no guarantee Oppy will make it to Endeavour, so when something so unique drops into your lap (or sandy suface as the case may be) you need to take advantage of it. At this point, there's no way to speculate what might be learned with the "free science" And there's no way to know when the end will come. This is much like human geologists would act. Sure you have plans, but when presented with something really special, you stop and investigate before you move on with the plan.

That is because they are being operated by real human geologists. Of themselves the rovers are not more geologists than a microwave oven is a chef.

Jon

 

[3488]

Enhanced colour view of Block Island Meteorite.

Infrared, Green, Blue filters, were enhanced to show compositional & erosional variations. It appears from this image & others that Block Island was once buried & has since been exhumed.

Andrew Brown.

 

[3488]

I've just had a little play around with the above image & think I have been able to produce a 'truer' colour one. I think it is more or less correct based on other colour images of the martian surface from all of the successful landers & also Block Island has kept that metallic grey, so I'm, reasonably confident that this is close to how a human being would see it.

It may not be 100% correct, but think it's not too far off.

Full size version here.

Andrew Brown.

 

[3488]

Sol 1,969 base of Block Island Meteorite. It is possible to see how the regolith is of a differing texture around the base of the meteorite & how Block Island is sitting on a 'plinth'.

Sol 1,968 Microscopic Imager image of a 3.1 CM by 3.1 CM area of Block Island.

Andrew Brown.

 

[MeteorWayne]

Sorry, I had to define the term :

In architecture, a plinth is the base or platform upon which a column, pedestal, statue, monument or structure rests.