Fungi thrive in radiation intense environments. Sequential photos document that fungus-like Martian specimens emerge from the soil and increase in size, including those resembling puffballs (Basidiomycota). After obliteration of spherical specimens by the rover wheels, new sphericals--some with stalks--appeared atop the crests of old tracks. Sequences document that thousands of black arctic "araneiforms" grow up to 300 meters in the Spring and disappear by Winter; a pattern repeated each Spring and which may represent massive colonies of black fungi, mould, lichens, algae, methanogens and sulfur reducing species. Black fungi-bacteria-like specimens also appeared atop the rovers. In a series of photographs over three days (Sols) white amorphous specimens within a crevice changed shape and location then disappeared. White protoplasmic-mycelium-like-tendrils with fruiting-body-like appendages form networks upon and above the surface; or increase in mass as documented by sequential photographs. Hundreds of dimpled donut-shaped "mushroom-like" formations approximately 1mm in size are adjacent or attached to these mycelium-like complexes. Additional sequences document that white amorphous masses beneath rock-shelters increase in mass, number, or disappear and that similar white-fungus-like specimens appeared inside an open rover compartment. Comparative statistical analysis of a sample of 9 spherical specimens believed to be fungal "puffballs" photographed on Sol 1145 and 12 specimens that emerged from beneath the soil on Sol 1148 confirmed the nine grew significantly closer together as their diameters expanded and some showed evidence of movement. Cluster analysis and a paired sample 't' test indicates a statistically significant size increase in the average size ratio over all comparisons between and within groups (P = 0.011). Statistical comparisons indicates that arctic "araneiforms" significantly increased in length in parallel following an initial growth spurt. Although similarities in morphology are not proof of life, growth, movement, and changes in shape and location constitute behavior and support the hypothesis there is life on Mars.
The discovery and subsequent investigations of atmospheric oxygen on Mars are reviewed. Free oxygen is a biomarker produced by photosynthesizing organisms. Oxygen is reactive and on Mars may be destroyed in 10 years and is continually replenished. Diurnal and spring/summer increases in oxygen have been documented, and these variations parallel biologically induced fluctuations on Earth. Data from the Viking biological experiments also support active biology, though these results have been disputed. Although there is no conclusive proof of current or past life on Mars, organic matter has been detected and specimens resembling green algae / cyanobacteria, lichens, stromatolites, and open apertures and fenestrae for the venting of oxygen produced via photosynthesis have been observed. These life-like specimens include thousands of lichen-mushroom-shaped structures with thin stems, attached to rocks, topped by bulbous caps, and oriented skyward similar to photosynthesizing organisms. If some of these specimens are fossilized is unknown. However the evidence of so many different types of life-like specimens make it almost indisputable that there is life on Mars. The overall body of evidence indicates are likely producing and replenishing atmospheric oxygen. Abiogenic processes might also contribute to oxygenation via sublimation and seasonal melting of subglacial water-ice deposits coupled with UV splitting of water molecules; a process of abiogenic photosynthesis that could have significantly depleted oceans of water and subsurface ice over the last 4.5 billion years; and, which would have provided moisture to these Martian organisms and their ancestors.
Billions of years ago, the Northern Hemisphere of Mars may have been covered by at least one ocean and thousands of lakes and rivers. These findings, based initially on telescopic observations and images by the Mariner and Viking missions, led investigators to hypothesize that stromatolite fashioning cyanobacteria may have proliferated in the surface waters, and life may have been successfully transferred between Earth and Mars via tons of debris ejected into the space following bolide impact. Studies conducted by NASA's robotic rovers also indicate that Mars was wet and habitable and may have been inhabited in the ancient past. It has been hypothesized that Mars subsequently lost its magnetic field, oceans, and atmosphere when bolides negatively impacted its geodynamo and that the remnants of the Martian seas began to evaporate and became frozen beneath the surface. As reviewed here, twenty-five investigators have published evidence of Martian sedimentary structures that resemble microbial mats and stromatolites, which may have been constructed billions of years ago on ancient lake shores and in receding bodies of water, although if these formations are abiotic or biotic is unknown. These findings parallel the construction of the first stromatolites on Earth. The evidence reviewed here does not prove but supports the hypothesis that ancient Mars had oceans (as well as lakes) and was habitable and inhabited, and life may have been transferred between Earth and Mars billions of years ago due to powerful solar winds and life-bearing ejecta propelled into the space following the bolide impact.
The finding of life on Mars, existing now or in the past, will certainly be one of the greatest adventures in the history of mankind. Further arguments are provided, strengthening an earlier claim, that among mineral bodies (dubbed "newberries"), imaged by the MER Opportunity in deposits of Late Noachian age (~3.8 to 3.6 Ga) exposed at the rim of Endeavour Crater (Matijevic Formation) objects occur that resemble fossils of Terran unicellular and colonial microalgae. The previously claimed algal affinities of these fossil objects is now supported by examples of "newberries" showing the presence of internal structures highly similar to daughter colonie characteristic for Terran volvocalean algae and cell-like objects enclosing objects reminiscent of chloroplasts characteristic for modern and fossil unicellular green and yellow green algae. A fluffy layer of stagnant water body is postulated as sedimentary environment promoting early post mortem silicification (Fe 3+ smectite) of the microalgae-like biota.
The unicellular Chroococcidiopsis is extremely resistant to desiccation, UV-irradiation, salt toxicity and high temperature. It requires only low light intensities for growth, and is protected against destruction from high energy UV-light by pigments such as carotenoids and scytonemin. Cyanobacteria, such as Chroococcidiopsis, have minimal nutrient requirements and can meet their nitrogen demand by means of the conversion of the atmospheric dinitrogen molecule to ammonium ions (nitrogen fixation). Water is the electron donor for photosynthesis, but can possibly be replaced by molecular hydrogen gas. A member of the genus Chroococcidiopsis is likely the best organism for exploring the potential for life on Mars. For this goal to be achieved, however, many strains exist on Earth that still must be explored to find the best suited one.
Throughout its mission at Eagle Crater, Meridiani Planum, the rover Opportunity photographed thousands of mushroom-lichen-like formations with thin stalks and spherical caps, clustered together in colonies attached to and jutting outward from the tops and sides of rocks. Those on top-sides were often collectively oriented, via their caps and stalks, in a similar upward-angled direction as is typical of photosynthesizing organisms. The detection of seasonal increases and replenishment of Martian atmospheric oxygen supports this latter interpretation and parallels seasonal photosynthetic activity and biologically-induced oxygen fluctuations on Earth. Twelve "puffball" fungal-shaped Meridiani Planum spherical specimens were also photographed emerging from beneath the soil and an additional eleven increased in size over a three-day period in the absence of winds which may have contributed to these observations. Growth and the collective skyward orientation of these lichen and fungus-like specimens are indications of behavioral biology; though it is impossible to determine if they are alive without direct examination. Reports claiming these Eagle Crater spheres consist of hematite are reviewed and found to be based on inference as the instruments employed were not hematite specific. The hematite-research group targeted oblong rocks which were mischaracterized as spheres, and selectively eliminated spectra from panoramic images until what remained was interpreted to resemble spectral signatures of terrestrial hematite photographed in a laboratory, when it was a "poor fit." The Eagle Crater environment was never conducive to creating hematite and the spherical hematite hypothesis is refuted. By contrast, lichens and fungi survive in Mars-like analog environments. There are no abiogenic processes that can explain the mushroom-morphology, size, colors and orientation and growth of, and there are no terrestrial geological formations which resemble these mushroom-lichen-shaped specimens. Although the authors have not proven these are living organisms, the evidence supports the hypothesis that mushrooms, algae, lichens, fungi, and related organisms may have colonized the Red Planet and may be engaged in photosynthetic activity and oxygen production on Mars.
During the Noachian period, 4.1-3.7 Gys ago, the Martian environment was moderately similar to the one on present Earth. Liquid water was widespread in a neutral environment, volcanic activity and heat flow more vigorous, and atmospheric pressure and temperature were higher than today. These conditions may have favoured the spread of life on the surface of Mars. The recognition that different planets and moons share rocky material cast in space by meteoroid impact entails that life creation is not necessary for each single planetary body, but could travel through the Solar system on board of rock fragments. Studies conducted on the past forms of Martian life have already highlighted possible positive matches with microbialite-like structures, referable to the geo-environmental conditions in the Noachian and Hesperian. However, by necessity, these studies are on predominantly micro and meso-scopic scale structures and doubts arise as to their attribution to the biogenic world. We suggest that in the identification of Martian life, we are currently in a position similar to the one of Kalkowsky who in 1908, based solely on morphological and sedimentological arguments, hypothesized the (now accepted) view of the biotic origin of stromatolites. Our analysis of thousands of images from Spirit, Opportunity and Curiosity has provided a selection of images of ring-shaped, domal and coniform macrostructures that resemble terrestrial microbialites such as the ring-shaped stromatolites of Lake Thetis, and stacked cones reminiscent of the group of terrestrial Conophyton . Notably, the latter were detected by Curiosity in the mudstone known as ‘Sheepbed’, the same outcrop where past organic molecules have been detected and where the occurrence of microbial-induced sedimentary structures (MISS) and of many more microbialitic micro, meso and macrostructures has already been hypothesized. Some of the structures discussed in this work are so complex that alternative biological hypotheses can be formulated as possible algae. Alternate, non-abiotic explanations are examined but we find difficult to explain some of such structures in the context of normal sedimentary processes, both syngenetic or epigenetic.
New images from Mars rover Curiosity display millimetric, elongate stick- like structures in the fluvio-lacustrine deposits of Vera Rubin Ridge, the depositional environment of which has been previously acknowledged as habitable. Morphology, size and topology of the structures are yet incompletely known and their biogenicity remains untested. Here we provide the first quantitative description of the Vera Rubin Ridge structures, showing that ichnofossils, i.e., the product of life-substrate interactions, are among their closest morphological analogues. Crystal growth and sedimentary cracking are plausible non-biological genetic processes for the structures, although crystals, desiccation and syneresis cracks do not typically present all the morphological and topological features of the Vera Rubin Ridge structures. Morphological analogy does not necessarily imply biogenicity but, given that none of the available observations falsifies the ichnofossil hypothesis, Vera Rubin Ridge and its sedimentary features are here recognized as a privileged target for astrobiological research.
This work details the laboratory analysis of a suite of 10 samples collected from an inverted fluvial channel near Hanksville, Utah, USA as a part of the CanMars Mars Sample Return Analogue Deployment (MSRAD). The samples were acquired along the rover traverse for detailed off-site analysis to evaluate the TOC and astrobiological significance of the samples selected based on site observations, and to address one of the science goals of the CanMars mission: to evaluate the ability of different analytical techniques being employed by the Mars2020 mission to detect and characterize any present biosignatures. Analytical techniques analogous to those on the ExoMars, MSL and the MER rovers were also applied to the samples. The total organic carbon content of the samples was <0.02% for all but 4 samples, and organic biosignatures were detected in multiple samples by UV–Vis–NIR reflectance spectroscopy and Raman spectroscopy (532 nm, time-resolved, and UV), which was the most effective of the techniques. The total carbon content of the samples is < 0.3 wt% for all but one calcite rich sample, and organic C was not detectable by FTIR. Carotene and chlorophyll were detected in two samples which also contained gypsum and mineral phases of astrobiological importance for paleoenvironment/habitability and biomarker preservation (clays, gypsum, calcite). They were detected and characterized by multiple techniques, of which passive reflectance was most effective. The sample selected in the field (S2) as having the highest potential for TOC did not have the highest TOC value, however, when considering the sample mineralogy in conjunction with the detection of organic carbon, it is the most astrobiologically relevant. These results highlight the importance of applying multiple techniques for sample characterization and provide insights into their strengths and limitations.
Araneiforms are radially converging systems of branching troughs exhibiting fractal properties. They are found exclusively in the Southern polar regions of Mars and believed to be result of multiple repetitions of cold CO2 gas jets eruptions. Araneiform troughs get carved by the overpressurized gas rushing underneath a seasonal ice layer towards a newly created opening. Current work is an attempt to quantitatively analyze araneiforms patterns and model their formation mechanism. The dendritic quality of most araneiforms are suggestive that they can be described in terms commonly applied to terrestrial rivers. We have adapted and for the first time applied to Martian araneiforms qualitative morphological analysis typically used for terrestrial rivers. We have shown that the large and well-developed araneiforms (with tributary orders larger than 4) closely follow Horton's law of tributary orders and have bifurcation ratio that falls well inside the range of terrestrial rivers. We have implemented a two-dimensional Diffusion-Limited Aggregation (DLA) model that describes formation of dendrite shapes by mathematical probabilistic means. We compared modeled dendrite shapes to the araneiform shapes observed in the Martian polar regions and evaluated their similarity using the morphological analysis of araneiforms. We showed that DLA model can successfully recreate 2D shapes of different observed araneiforms. Modeling the creation of araneiform patterns with DLA leads to better understanding of seasonal processes that create them.