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Stromatolite Identification Site

Stromatolites are the fossilized remains of microbial life forms, primarily algae and cyanobacterial mats. A more formal definition has been "laminated organo-sedimentary structures formed by the trapping and binding, and/or precipitation of minerals by microorganisms". The above definition comes from a page on the NASA Astrobiology Institute Stromatolite web site. These microorganisms were among the earliest life forms to evolve on earth, some of them existing 3.5 billion years ago. Thus their remains give us the oldest large-scale evidence of life on earth.

The exploration of Mars will have as a key component exo-paleontology, or the search for evidence of off-planetary past life forms. There is evidence that oceans did exist at some point on Mars. A key question is whether they lasted long enough to enable primitive life forms to evolve. If they did evolve, then their evidence would presumably be left in a form similar to that on early earth, Mars stromatolites.

The search for evidence of past Martian life forms will be carried out by a series of Mars rovers, and at some point, Mars human explorers. Both Mars rover controllers and human explorers will be primarily engaged in sample collection for geological, paleontological and biological analysis. These samples will be either returned to earth or analyzed on-site. The ability of those choosing samples to recognize potential remains of primitive life forms is crucial to the success of these missions.

Thus familiarity with a wide variety of earth stromatolitic forms is a key component of the training of Mars rover controllers. This site attempts to display a wide variety of stromatolite forms to that end.


A number of classification systems have been put forward during the last century for stromatolites. Many of the characteristics used to classify stromatolites have depended on microscopic features. While these are useful for their intended purpose, the purpose of this site is to enable recognition of stromatolite forms in the field. Thus a very tentative classification system will be proposed based on macro features readily observable.


Click on the pictures for a larger view  

Traditional Spheroid Forms

Click here for all Spheroid Forms
The first stromatolites studied were in the form of dome-shaped colonies, with the convex surface uppermost.
Thick Mats Click here for all Thick Mat Forms
This series shows the mats of cyanobacteria laid down between the intervening sediments, in this case dolomite limestone.
Click here for all Thin Mat Forms
Similar to the above, except the layers are smaller.

Click here for all Diffused Forms

The mats in this case are scattered over and through the matrix.

Click here for all Bumpy Forms

Similar to the traditional spheroid form but with very small colonies.

Click here for all Crusty Forms

The colonies are irregularly spread over the surface of the matrix.

Click here for all Combo Forms

Where two or more types are close together.

Click here for all Veined Forms

The stromatolites are embedded in the surrounding sediments and have been replaced with minerals forming veins.
Indented Click here for all Indented Forms
The stromatolites or their sediments have been weathered out, forming voids.
Weathered Click here for all Weathered Forms
The stromatolites and their supporting sediments have been weathered, forming unique and interesting forms.
Mars-Like Rocks

Click here for all Mars-Like Rocks.

These are some stromatolite forms that resemble Mars Land Forms.


Neutron/Gamma ray Geologic Tomography (NUGGET) instrumentation to search for Stromatolites

Movie: "NASA's Stromatolite Explorer: an Investigation of a Microbial Mat Community"