New image sugests spherules are fossils rather than concretions

Recently, I noticed this new image from sol 124 by pure chance, see the beautiful double spherule. It looks to me more like it is biogenic then a simple mineral concretion.

It is difficult to qunatify why something as simple as a double spherule would be sugestive of biology rather than mineralogy. Certainly, one would expect concretions occasionally to merge and form a double or even tripple spherule, as we have seen. But, to me, this one looks more like two spherules are being squished together, or maybe in the process of separating, rather than simple mineral growth overlapping. Does anyone else get a similar impresion? There is a good reason for this.

Although it might at first seem impossible to distinguish these to cases, there is a logical, objective way to do this. Consider the mechanism of mineral growth in a concretion. Once the concretion is nucleated, mineral growth occurs as a chemical reaction on the surface of the concretion, with a uniform rate in all directions, which is the source of the spherical form. The reason for this is that the growth must occur at the surface of the concretion and proceed outwards uniformly, since the rate is dependent on the surface are of the mineral concretion. Where two concretions grow close to one another, the mineral growth should be accelerated in the contact region, since the surface area is increased near the contact. This will tend to gradually smooth out the contact regions, and produce an increasingly obtuse angle between the surfaces of the two concretions as they grow.

Howevewr, look at the angle between the spherules in this image, where they contact, the angle is accute, as if either two spheres with a suface membrane are being squished together, or alternatively they are dividing. If this were two mineral concretions growing together, you would expect the angle of contact to be obtuse, as mineral growth would be accelerated in the contact region, because there is more surface area on which additional mineral growth can occur. This accelerated growth would form an obtuse angle. So, this one double spherule is more consistent with biogenesis rather than mineral concretions.

If you look at examples of moqui marbles, they do exhibit the behavior I sugest is predicted for a concretion, this is very common, but they do not form double spherules like the one we see here.

Here is an example of moqui marbles, aka utah berries, showing several examples of coonretions merging together:

source reference

Hey! Those moqui marbles also got a resemblance to the 'Pot of gold' to some degree. Thanx for posting the image, aint got anything such locally but seeing that image things snapped into perspective for me.

r_lewis, I pointed them also at "Late Oppy images", in a different context.
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Reply 2.

Secondary mineral concretions can in fact grow together as shown, if they nucleate in close proximity. Besides, inumerable images from the Opportunity microscopic imager show the fine layering of the host sulfates to be truncated by the spherules, clearly demonstrating they are secondary features that grew within the rock after deposition. If they were fossils or impact/volcanic spherules that originated before or during formation of the layers, the layers would distinctly wrap around them.

The "compressed" double spherules at the Opportunity site are interesting. They might be organic or inorganic in origin.

I have collected Ordovician age sandstone spherules/concretions in Wisconsin, Illinois near the boundary of the St Peter Sandstone and the Platteville. These concretions exhibit many morphologic characteristics similar to the mars spherules.

The Ord. concretions may be fossil remnants of biological activity or they may be inorganic. Biological activity can occur after deposition and can result in cementing or even altering the deposited sediment, there are many examples of this. A fossil is not necessarily something that occurs exclusively during deposition and may occur after deposition.

Ordovician age sandstone spherules/concretions appear to have formed within the sandstone, after deposition. Sedimentary layers can be noted within some of the Ordovician concretions and they do not appear to deform the surrounding sandstone sediment.

Many images of the Ord. sandstone spherules/concretions are at:
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I have recently taken images of some of the double Ord. concretion morphological differences that I have noted. Some appear compressed and others are less compressed. I hope to find someone interested in performing a thin section on 1 or more of these intriguing doubles.

Courtesy of RPage (Ref. Reply 4):

/R

marsman

I can't help but relate the Mars berries to some type of bacterial fossils.
Is it not possible some type of replacement process is at work?

strings of berries

Doubles triples budding

Spherules with a possible uniform size distribution profile that show doubles and triples.

Hmmm...

Mann,

Could I have you post the website links for the images in Reply 6?

Thanks!

Very Respectfully,

marsman