Life on Mars? Possible endolithic microbes from sample 11-18h.

EVA and Labwork: Today we did a midday EVA back to Cow Dung Reservoir (Lith Canyon) to explore in greater detail. The effort paid off, and I found varied samples of candidate hypoliths and endoliths and have now looked at them in the lab. The following is a run-down of my preliminary findings:

• Sample 11-18a was a candidate hypolith from beneath a rock embedded in the streambed above Lith Canyon where we disembarked from the ATVs. The moist patch of soil beneath the rock contained a much lighter area that suggested mat material, and it is from this that the bulk of the sample was retrieved. On inspection under the stereoscope, the lighter material is just some differently colored sand. There is a bit of vegetation, primarily root material, in the sample, but since these are unlikely to have analogues on Mars (being rather advanced life forms with parts that live on the surface) they are of not so much interest to this study.
  
  
• Sample 11-18b was also a candidate hypolith from the streambed. It was quite different from 11-18a, however, in that as opposed to a large patch of potentially sand material, it resembled a dollop of grey paste about two cm in size and elevated about 2 mm from the cavity of the rock that had previously been covering it. I am confident it was organic, but possibly an animal waste product, although there did not appear to be any animal burrows or other paths under the rock that would have allowed such to get underneath. Unfortunately, a similar sample will have to be re-acquired, as this particular one may have been misplaced in the field!
  
  
• Sample 11-18c was collected from the lower canyon area, because it had some interesting white speckling on hypolithic mud. Under the stereoscope, however, the white speckles are just a dusting of lighter colored sand.
  
  
• Sample 11-18d was similar to 11-18c in that it had white speckling, but the sample endolithic, contained in a large horizontal fracture within a large (30cm) rock. Also, the white speckling was interwoven by fibrous material that appeared to be in place, as opposed to washed in . In lab, the white speckling is again lighter colored sand, while the fibrous material is made up of thin (<1mm) plant roots. My suggestion is that a plant wedged its roots into the rock prior to the rock's arrival on the barren canyon floor.
  
  
• Sample 11-18e is a conglomerate with constituents <1cm and a light brown crumbly matrix. It appeared to have a tiny vascular plant (2mm, resembling a light green flower bud) growing in an interior cavity when examined in the field, but the same could not be found under the stereoscope.
  
  
• Sample 11-18f was a candidate endolith from green shale, consisting of a brown texture over the green rock. Stereoscopic examination was inconclusive, so I looked at it in the microscope. At 800x, tiny spheres could be discerned, suggesting a cellular component-Finally, an extant Martian lifeform! The spheres connected to each other in clusters and chains of five to a dozen members, and were associated with the mineral particles.
  
  
• Sample 11-18g was an in place grey sandstone from the canyon wall with a brown varnish. The area of geobiological interest was the somewhat redder-brown deposits on the interior fractures. Similar to the brown deposits of the green shale, they also showed tiny spherical structures at 800x in the microscope. No chains were visible, but the clusters were larger and were associated with large mineral particles.
  
  
• Sample 11-18h was a more weathered grey sandstone, collected from the canyon floor. At 800x, tiny spheres were less common than in 11-18g and f, but were present and again associated with mineral particles.

At this point, it would be easy to say that we have found an endolithic organism and a good analogue for what we are searching for on Mars. However, this may not be the case. Many features that would be expected of a true, endolithic community are missing, like filamentous material, diversification between layers, or layers of any kind, for that matter. The tiny, homologous spheres are more suggestive of isolated bacteria, possibly bacteria that were washed into the rock fractures and embedded in a brown mud crust. If this is the case, the organisms aren't quite as interesting to us as we try to extrapolate to the search for life on Mars, since they would not be specialized for an "extreme" lifestyle, such as living inside a rock.

However, these bacteria could be living within the rock, and thus still be a good analogue for Martian extremophiles, similar to Heterococcus sp. (Xanthophyceae) as described by Imre Friedman in1982 (Science, v.215, pp.1045-1053). All that is needed is some control samples from the surrounding soils to see if the tiny spheres are ubiquitous there, as well. If they are, we cannot conclude that we have discovered an endolithic organism. If they are not there, we can be a bit more optimistic that we have!

LSS: Coliform results from samples taken the 15th are more or less the same as earlier samples, although they were not monitored as closely as earlier samples due to the extended EVA Sunday. But if the blue fuzz on the tap-sample petri dish can be assumed to be slower growing non-coliforms, the UV-irradiation is still doing its job.