Curious stones

Take a look in the foreground in this image.
There are at least four objects that appear to be carved out of stone.
What is up with the arrow head?
Richard

Not a sigle curious person in the bunch?
I marked a few. The arrow head is supported by a small "post". The sand goes under both sides. the others just seem a bit too perfect
R

Rich,

Gee, I wonder where you got the idea of using the neon green arrows?

Thanks for the help though, as now I can see what mean. What interests me is that object on the lower right. It reminds me of the item I noted in this thread, [A little too symmetrical]

As you and I have discussed, I'm seeing more and more bevel edged as well as 90 degree angular items. I could start a study just on the "beveled edge" stuff.

I think it's only statistics...
but up to now I haven't seen any crystal-like structure....
Do anybody knows if it is possible to observe any kind of crystals without any rock grinding?

Certain types of rock tend to fracture in predictable ways.

Ok and I do understand that Daniel but look again with some zoom on the arrow head.
somehow it just dosnt look natural to me
R

Hi Richard,
A lot of different types of minerals tend to splinter into regular angular shapes when broken. Especially if broken by a sudden impact (a meteor or sledgehammer)

If you are ever in NY, try catching the Hall of Minerals at the American Museum of Natural History. They have a great display sorting different rock types by the forms they tend to fracture into.

If you want to do an internet search on the subject - the technical term is Cleavage.

Minerals have a lot of different attributes - the relevant ones here are Cleavage (the tendacy of a mineral to break into one or more regular planes) and Fracture (the patterns formed when it breaks irregularly)

I understand Daniel
The feature I am most curious about is the arrow head. Balanced upon a post. when you lighten this photo you can see under both sides of the rock around the center post. I also can understand cleaving. what I am having problems with is the symetry of that feature. The right angles on both sides next to the "post" with the length of those horizontal lines being in exact proportion and then both sides intersecting at the top to form the triangle. Probably natural but darn odd.
R

It is a curious looking shape certainly - and probably won't be the last one we see.

Smash a lot of rocks + expose 'em to wind for a few million years = lots of cool shapes.

Those stones are interesting.

There are a couple of other stones that are also curiously shaped that I've highlighted.

Welcome To the mars rover Forum bonker!
Richard

Thanks.

Mars is a fascinating place.

Richard and all, these sorts of shapes are common in deserts on Earth. The 3-cornered pyramidal stones are known as dreikanters (3 corners) and here's a good terrestrial example.

http://www.uwgb.edu/dutchs/EarthSC202Slides/windslid.htm

You can also have einkanters etc. The processes that produce these are quite well known and involve the erosion at a short distance above the ground by wind carried sand - which falls and knocks up more sand - a process known as saltation.

Wind-eroded rocks can assume all sorts of fantastic shapes, here are some terrestrial examples known as ventrifacts and many bear remarkable resemblence to the wierd shapes many of you have been commenting upon.

The first is a talk about desert erosion processes and has a nice picture of a dreikanter and a great picture of mushroom rock in Death Valley which I'm sure is how many of the vertical 'plant' features you've been discussing are produced.

http://geosun.sjsu.edu/paula/134/pdf/lecture20.pdf

The second is a good compilation of pictures of desert erosion features

[link]

and the 3rd a comparison between features seen at the Viking and Pathfinder sites and Earth erosional features.

http://www.agu.org/pubs/sample_articles/sp/2000JE001481/2000JE001481.pdf

Try all of these links, they show you some good examples of what erosion on Earth can produce and the same processes will occur on Mars.

Having said all that, whilst I am quite confident that the shape of the 'arrow head' you pointed out was produced something like that, it does look 'balanced' on top of another stone and I don't know how that happened. If only we had a better picture maybe we could tell.

Ian,

Finally someone on here has tried to make an argument for the opposing side. I shall be stuttering over this for days.

Amalgamale, many people, including me, have tried to introduce some science into this forum many times over the last few months and they have said what I said above and in better ways covering more features.

I do not see that there are 'opposing sides', there is a broad spectrum of opinion here and it is divisive to pigeon-hole people into opposing camps. There is only ONE person here (I hope I do not misquote him - Serge) who doesnot believe that there is or was some chance of life on Mars although many people here believe that if it does or did exist it was likely confined to microbial organisms. In my view the chance of larger organisms is highly unlikely but I will look at evidence. In my opinion, none that has come forward yet is at all compelling.

I'm not sure what you mean by stuttering but thank you for acknowledging my lucky post 13 and that you will read it.

RW > I agree, finally a statement...

Ian > ok by me.

yt
dx

i agree that these rocks are very interesting in their physical appearence.

although i do not see the general interest in features which are clearly the result of abrasion by wind blown particles.... we already know that the climatic conditions of mars is dominated by intense wind storms.

i believe it is neccessary to search for erosional features that result from fluvial action. i do realise that terrestrial based photographs are only of a liminted area.
with that said:
is there any small scale evidince of fluvial action from the rover footage???

if so, i belive that this would be of greater importance to answering the ultimate question "was there life (of any form) on mars".