Spirit Finds Stromatolite Fossils

More stromatolite images from Spirit in Gusev Crater

BACK

   There are many more images of stromatolite fossils in the Spirit data.  Here is a second stromatolite from Sol 105.  I have also tinted the false color frame for this stereo image from the right panoramic camera.

This is from Spirit Sol 091.  The strange "shell" of a rock in the image hinted at an unusual origin, and I suspected that this might be a stromatolite, but until I had a perfect image such as the Sol 105 image, it could not be proven.    Now that we know that stromatolites lived in Gusev Crater ages ago, we can safely conclude that this, too, is a stromatolite fossil.    So this is a third stromatolite fossil.  The original image is here.  And the sharp-eyed observer will spot many other remnants in this picture.  Click the image for a larger view.    It becomes clear from the full sized color image that this was a stromatolite colony, with three and perhaps more of the organisms in this location.
This image from Spirit Sol 070 shows a rock with a "shell" around it and the thin walled rock outline as well.  The top center rock has what appears to be a shell over it.  There is also another rounded "column" rock to the right of it.    The dark thing is the Spirit rover's wheel print.  The soil below the surface is much darker than the upper soil layer.    Now for the magnified view.  Click the image for the larger picture.

This image shows two unusual sights.  The first is the stromatolite at top and left (and possibly a second one just below it) and the other is the rounded thing to the right.    This object is identical to one seen in the very first images of the ground when Spirit landed.    The stromatolite is circled in blue, the "log" in red.

    Now, given that there are stromatolites, we can concentrate for a moment on the "log" object.  The stereo image above seems to show that it is rounded and has a central feature of some sort.  There is a cylinder shaped object with a smaller cylinder in its center.  Are there more of these things present?

Spirit Sol 007, very early on in the mission.  This shows a landing bag print on the soil and a number of rocks.  But in the middle of the print is a strange rounded object that stands out at once.    Click the image at the right for a larger picture.
This shows the object in better detail.  It appears to be like a log or a stump- a circular object with a smaller circular object at its center.  This is exactly like the object from the right of the Sol 070 image above.    Now, can we confirm that it is truly the same shape and structure?  That would require a stereo image, and as it happens, we have the information for one available.
This is a monochrome image of the object.  I have circled it in red.  This is a cross-eyed stereo image.    Right away it leaps out at you.  This is definitely a cylindrical object that is hollow and has a second smaller cylinder at its center.  This is a second of these objects, and it is projecting out of the ground, like a stump.  The landing airbag bounced right on top of it.    The infrared spectra also match that of the stromatolites from above, and in all cases the stromatolites show the same infrared signatures within very small errors.    In other words, these objects are all carbonates, and have regular structures, and were made by living organisms.  They are all fossils.

Conclusion

    There are many stromatolites in Gusev, proving that it was a lake at some time in the past.  Furthermore, the images were often taken in full-spectrum by NASA, providing me with reference data for carbonate minerals on Mars.  I now have the proper infrared data to positively identify them in any image once I have the lighting conditions from the calibration images.

    I can absolutely say that carbonate minerals are present in large quantities in both Gusev Crater and at Meridiani Planum.  Both rovers are in areas full of fossils and carbonate minerals.  Their erosion explains the carbonate composition of the dust all over the planet.  There is between 2% and 5% carbonate in the dust that blows all over Mars today.

Wait a minute- aren't stromatolites made of silica?

    Stromatolites vary in composition, but many are made of calcite- calcium carbonate.  The form it takes depends on the type of bacteria or algae that formed the stromatolite, as well as the type of structure that it took.  It is clear that photosynthesizing organisms, such as cyanobacteria or blue-green algae, were very common as stromatolite organisms.  But there is also some good evidence that other types of bacteria could have formed stromatolites as well.

    Some stromatolites are made of silica or chert- a form of quartz (cryptocrystalized quartz).  This happens when the original minerals are replaced by silica through the action of water. Some geologists think that these silica stromatolites were able to precipitate silica directly, but in fact, it appears that they were calcium carbonate at first, and later the silica replaced their substance.  Here is a reference for this action.

    Stromatolites, when analyzed, prove to be made of magnesium, sulfur, silicon, and calcium compounds but are primarily calcium carbonate.  Based on these and other geological and paleontological references, I have chosen to accept the multiple spectrum data from NASA as the signature for calcium carbonate.

DONE            BACK