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Curiosity's observation of a peculiar crust outcropping, taken on Sol 890 (a); frame (a1) shows a blow-up of one of the putative fossilized thrombolite. Image Mastcam, NASA/JPG-Caltech/MSSS. For a better morphological comparison with terrestrial microbialites, the inset frame (b) shows a similar terrestrial thrombolites crust (Australian stromatolite).
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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 su...
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... examples of thrombolitic structures and crusts were also observed at meso scale on Mars and reported in previous works ( Rizzo and Cantasano, 2017, their fig. 9, and fig. 13 frames VI-X). In this work, they found shapes reminiscent of possible thrombolite structures; some of which show large lumps inserted in thin-leaf sediments. Similarly, Fig. 4 shows a comparison between a biogenic build-up of a thrombolite (deposited in a quiet environment) and a blow-up of an image shot by Curiosity, showing a crust over thin-laminated sediment. The possible physical or chemical processes involved in such thrombolitic crusts over or inside thin-laminated sediment are hardly explicable. ...
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... is geometrically similar to those described in the previous Figs. 6 and 7. Such peculiar and complex bodies are reminiscent of microbialitic forms that grew parallel to each other, and in particular the widespread genus Conophyton consisting of superposed cones. We find some similarity of this group with the toppled reef of Conophyton reported in fig. 4a of Kah et al. (2009) or to some green dasyclad fossil algae (Flugel, 2010). ...
Citations
... In addition they could represent the remains of petrified algae (Joseph et al. 2020a), fungal fruiting bodies (Joseph et al 2021b), or be 'trace fossils' such as sand filled worm burrows (Joseph et al. 2020b(Joseph et al. , 2021c. Detailed examination of the rock surfaces at the site between sols 3786 and 3800 ( Figure 13) suggest the presence of surface features reminiscent of fungi (Joseph et al. 2021) or algae (Joseph et al. 2020;Rizzo & Cantasano 2009;Bianciardi et al. 2014Bianciardi et al. , 2015Bianciardi et al. , 2021Rizzo et al. 2020Rizzo et al. , 2021. These features include filaments, rows of spherules, and tube-like structures suggestive of the presence of possible microbialites. ...
Unusual horizontal protrusions were photographed on rocks in Gale crater, Mars by the Curiosity rover 'Mastcam' and 'ChemCam' between sol 3786 and 3800. These protrusions follow horizons of bedding in the sedimentary rocks and have a variety of morphologies including 'spike-like', blunt 'wedge-like', 'plate-like', or 'serrated' protrusions. These features have resulted in considerable speculation as to their origin with both biogenic and geological explanations being suggested as well as the possibility they may represent debris from a saucer-shaped extraterrestrial space craft. Quantitative analyses of the spikes and wedges document significant uniformity in morphology and orientation. In addition, auto-correlation analysis of 12 samples of protrusions suggests they are random, clustered, or regularly distributed along the laminae. One rock outcrop, with many laminae affected, exhibits a considerable degree of concordance in position of the protrusions. The probability that this may be the remnant of any of the Mars orbiters or other terrestrial craft that crashed in Gale Crater is not likely as there is no apparent analog to any Mars-bound equipment and no evidence of a debris field, although a fragment from an extraterrestrial or terrestrial space craft cannot be discounted with absolute certainty, particularly in that fragments including what appears to be wheels, an axle and a cratered debris field have been photographed in another Gale Crater location. It is not likely that the spikes are a consequence of lightning or electromagnetism in the early life of Mars despite the high concentrations of magnetic minerals in the sediments. A possible explanation is a type of sand concretion known as a 'sand spike' formed in the presence of water, sand, and possibly seismic activity. The protrusions are also associated with surface features reminiscent of fungi and/or microbialites suggesting a biogenic component in their formation. Hence, the protrusions appear to be sand concretions revealed as a consequence of weathering and may result from various contributory factors; the most likely being water, seismic activity, and the activities of microorganisms. .
... Studies are frequently limited by the lack of clear definitions of concepts (i.e., Bartley et al. 2000, Riding, 2008, 2011a, Mata et al. 2012. Although the literature is very extensive (Grey and Awramik 2020), efforts at a holistic approach to description must begin with the establishment of a consensual and definitive glossary applicable to stromatolites on Earth, as well as to suspect structures on rocky surfaces elsewhere in the solar system, such as the lake and playa-lake deposits targeted for paleobiological exploration on current and future missions to Mars (i.e., Bianciardi et al. 2014, Rizzo 2020. ...
Abstract Stromatolites are laminated biosedimentary structures of great importance for paleobiological, paleoecological, and paleoenvironmental analyses, mainly in Precambrian rocks. Their value is related to the glimpse of past life recorded in their lamination, fabric, and, eventually, due to the preservation of organic matter, including microfossils, and because their deposition is directly influenced by environmental conditions. Although stromatolites are widely described in microscopic scale, there is a lack of standardization of their nomenclature, precluding better paleoenvironmental and paleobiological interpretations. In this study, we propose a guide for the microscopic analysis of fossil stromatolites and, possibly, thrombolites, and provide a review of specialized literature and the bibliometric context of main terms. The goal is to contribute to the improvement of their application through systematization of microscopic data, in the face of novel paleoecological and paleobiological approaches and for astrobiological prospection for microbialites in therock record of Mars.
... In addition to Martian acritarchs fossils, fossilized algae (11)(12)(13)(14)(71)(72)(73)(74)(75)(76), and the fossil remains of microbial mats, microbialites, and concentric stromatolites (5,11-17, 73, 76)--which, on Earth, are constructed by algae and cyanobacteria--have also been discovered on Mars. The concentric stromatolites are in fact nearly identical to the concentric stromatolites of Lake Thetis, Australia [14,76]. ...
A substantial body of evidence supports the theory that life began on Mars billions of years ago as based on discoveries of microbialites, stromatolites, and fossilized cyanobacteria, green algae, acritarchs and biochemical studies of Martian meteorites. As based on evidence, there followed an evolutionary progression within the oceans, lakes and seas leading to metazoan invertebrates. Subsequently, much of metazoan marine life became extinct leaving fossilized remnants resembling sponges, corals, annelids, tube worms, trilobites, crustaceans, sea spiders, scorpions, arachnids, and the trace fossils of mollusks and bivalves. It's hypothesized that numerous species may be frozen in glaciers. According to evidence-based theory: Chaotic obliquity and related increases in temperature and atmospheric pressure have repeatedly led to glacial melting and flooding of oceans of melt-water that stabilized and, in which, life flourished and evolved. When axial tilting declines there follows a receding and then freezing of what had been rivers, lakes, and vast seas and which led to the extinction and fossilization of marine fauna. The global magnetic field may be linked to and wax and wane in parallel with obliquity and both may be related to a slashing collision with a comet or moon-sized astral body, possibly leaving Valles Marineris in its wake, thereby contributing to this mass extinction. Volcanic eruptions may have been contributory. Bacteria, algae, fungi, lichens and those organisms dwelling within caves, crevices, beneath the surface and within aquifers, and those upon the surface and who could adapt, have survived.
... Green specimens similar to algae have been observed upon rock-like sediment in Utopia Planitia and Chryse Planitia [1][2] and those with features similar to green algae and cyanobacteria have been photographed in Gusav Crater and Gale Crater [3][4][5][6][7][8][9][10][11]. In addition, formations closely resembling microbialites and concentric stromatolites--presumably constructed by cyanobacteria and green algae-have been observed in several locations on Mars, Gale Crater in particular [3,7,9,[12][13][14][15][16][17][18][19][20][21][22]. ...
Multiple specimens that closely resemble calcium encrusted cyanobacteria (blue green algae) were photographed by NASA's rover Curiosity in Gale Crater, Mars, several having a blue-green coloration. Comparisons of sequential photos, taken three to five days apart, indicate that putative cyanobacteria are growing, changing shape, multiplying, and secreting spreading pools of what may be calcium carbonate. Specimens that resemble algae/cyanobacteria were first observed during NASA's Viking Mission and have since been reported in other areas of Mars. Structures resembling microbialites and stromatolites-presumably fashioned by cyanobacteria-have been previously observed in Gale Crater. Cyanobacteria are also primary oxygen producers and the Martian atmosphere is continually replenished with oxygen. Some of the specimens reported here may have been infiltrated by fungi. It has been previously reported, based on sequential photos by the rovers Opportunity and Curiosity, that fungi grow, change shape, increase in size, and multiply. The observations and photos presented in this and other reports strongly support the theory that biologically active cyanobacteria have colonized Mars.
... The buildup of minerals, metals, crystals, may also take unusual shapes. Therefore, it could be argued that the fossil-like structures reported here and in earlier reports, including those interpreted as concentric stromatolites similar to those of Lake Thetis Australia [1,13] are evidence of abiogenic and aqueous processes that have played a major role in the surface geology of Mars. However, there are no abiogenic terrestrial analogs and thus, the abiogenic explanation must be classified as speculation. ...
... The problem with the "imaginative cloud" interpretation is so many diverse and nearly identical forms are morphologically similar to those of Earth, and most appear within a few cm of each other and on substrates located in multiple locations in Gale Crater and other areas of Mars. For example, what may be tube worm and worm tube ichnofossils have been observed upon the dried lake bottom of not just Gale Crater [5][6][7][8] but Meridiani Planum [13] and Endurance Crater which may have hosted a lake or sea heated by thermal vents [14,15]. Likewise, specimens resembling microbialites and stromatolites have been observed in Gale Crater and other areas of Mars [16][17][18][19][20][21]. ...
... A large body of published evidence by over 30 investigators supports the hypothesis that a variety of organisms flourished and evolved in those waters [1][2][3][4][5][6][7][13][14][15][16][17][18]20,21,25,[34][35][36]. It is our hypothesis that the fossil-like forms reported here may include bottom dwelling (benthic) and free-swimming (nectonic) organisms that likely survived by filter feeding or upon the organic content drifting down and accumulating on the floor of Gale Crater lake, or via predation or the scavenging of dead organisms. ...
An array of formations resembling the fossilized remains of Ediacaran and Cambrian fauna and other organisms have been observed embedded atop sediments in the dried lake beds of Gale Crater, Mars. Specimens similar in morphology have been found together, or upon adjacent and nearby rocks and mudstone.These include forms morphologically similar to polychaete and segmented annelids, tube worms, "Kimberella,” crustaceans, lobopods, chelicerates, Haplophrentis carinatus, and the “ice-cream-cone-shaped” “Namacalathus” and “Lophophorates.” All specimens may have dwelled in a large body of water and may have been fossilized/mineralized following the rapid receding of these waters. Statistical quantitive micro-and macro morphological comparisons with analog organisms from Earth support the fossil-hypothesis. It is highly unlikely that these specimens were fashioned via abiogenic forces including wind, mineralization, crystallization, dried mud, or water-erosion scenarios. Collectively, these putative fossils could represent the equivalent of a “Burgess Shale” and the remnants of Martian organisms that long ago flourished in the lakes and inland seas of Gale Crater, Mars.
... If this were the case, then these microorganisms must have affected the surface and subsurface geomorphological characteristics of the planet, and it is thus appropriate to search the Noachian sedimentary record of Mars for biosignatures (Naylor, 2005;Cady and Noffke, 2009;Schon et al., 2012;Noffke et al., 2013;Westall et al., 2015;Corenblit et al., 2019;Joseph et al., 2020;Rizzo, 2020;Bosak et al., 2021;Noffke, 2021). ...
Microorganisms play a role in the construction or modulation of various types of landforms. They are especially notable for forming microbially induced sedimentary structures (MISS). Such microbial structures have been considered to be among the most likely biosignatures that might be encountered on the martian surface. Twenty-nine algorithms have been tested with images taken during a laboratory experiment for testing their performance in discriminating mat cracks (MISS) from abiotic mud cracks. Among the algorithms, neural network types produced excellent predictions with similar precision of 0.99. Following that step, a convolutional neural network (CNN) approach has been tested to see whether it can conclusively detect MISS in images of rocks and sediment surfaces taken at different natural sites where present and ancient (fossil) microbial mat cracks and abiotic desiccation cracks were observed. The CNN approach showed excellent prediction of biotic and abiotic structures from the images (global precision, sensitivity, and specificity, respectively, 0.99, 0.99, and 0.97). The key areas of interest of the machine matched well with human expertise for distinguishing biotic and abiotic forms (in their geomorphological meaning). The images indicated clear differences between the abiotic and biotic situations expressed at three embedded scales: texture (size, shape, and arrangement of the grains constituting the surface of one form), form (outer shape of one form), and pattern of form arrangement (arrangement of the forms over a few square meters). The most discriminative components for biogenicity were the border of the mat cracks with their tortuous enlarged and blistered morphology more or less curved upward, sometimes with thin laminations. To apply this innovative biogeomorphological approach to the images obtained by rovers on Mars, the main physical and biological sources of variation in abiotic and biotic outcomes must now be further considered.
... Stromatolite-like structures were also found by NASA rovers Opportunity, Spirit and Curiosity on the laminated Martian outcroppings of Meridiani Planum [12][13][14][15][16][17][18]. These findings have given strength to the hypothesis of stromatolites presence [19], that could be probably quite widespread from the Noachian to the Hesperian geological era of Martian life. ...
... Morphological study of images reveals evidence of widespread occurrence of micro, meso, and macro structures recalling for some authors early terrestrial forms of life; such as the "blueberries", concretions possibly induced by chemolithoautotrophic bacteria [10,36,37]. These strange and complex structures, for which abiological explanation it's hard to find, have strong morphological parallels with terrestrial microbialites/stromatolites [14][15][16]18], a conclusion that seems to be supported by morphometric approaches [12,13]. Other possible biogenic structures have been observed on Mars, recalling those of terrestrial silica deposits in hydrothermal environments [38,39] or typical structures, known as Microbially Induced Sedimentary Structures (MISS) and generated by microbial mats of intertidal environments [14]. ...
... Very interesting structures and morphologies were also observed, in addition to the many already cited, possible microbialites on the Sheepbed mudstone and structures recalling terrestrial microscopic induced by sedimentary structures, known as MISS, locally present as "erosional remnants," "pocket," "mat chips, "roll ups," "desiccation cracks," and "gas domes" [14]. Other possible microbially induced structures were also observed at this site, e,g., burst bubbles, filaments, mini-atolls, oncoids, domes and many other atypical sedimentary structures known as microbialitic [17,39,50], and some of which resemble stromatolites of the "Conophyton" type [18]. However, the morphology together with the chemical data mutually support the presence of ancient life, even if analyzed individually, they suggest alternative abiotic interpretations. ...
... To date, over 500 000 photographs have been uploaded from 'Curiosity' alone and include panoramic views of the Martian landscape and detailed close-ups of pebbles, rocks, boulders, and soil using the 'Mars Hand Lens Imager' (MAHLI) camera. Some of these photographs have been reported to reveal evidence of past life in the form of putative fossils, such as stromatolites, microbial mats, and calcareous algae (Bianciardi et al. 2014, Baucon et al. 2020, Rizzo et al. 2020, Joseph et al. 2020, or of actual living organisms including algae, fungi, and lichens (Dass 2017, Joseph 2014, Rabb 2018, Small 2018, Joseph et al. 2019, Joseph et al. 2020a,2020b. The information which can be obtained from these photographs, however, is often limited, difficult to interpret, and highly controversial. ...
... In addition, populations of lozenge-shaped objects resembling 'rice grains' and embedded in the mudstone and siltstone at the base of Mount Sharpe (McBride 2015) were detected by Curiosity in Gale crater (Sol 809, 880) and interpreted as 'pseudomorphic mineral crystals' of sulfate such as gypsum or jarosite ( Figure 2) (Martin et al 2017). Nevertheless, these structures may also be interpreted as evidence of life, e.g., the blueberries resemble the fruiting bodies of some fungi or lichens and the'rice grains' types of terrestrial fossil algae (Rizzo et al. 2020, 2021, Joseph et al. 2020a). ...
Pattern analysis describes a series of statistical methods to determine whether a variable shows significant changes in space or time and with applications in many scientific fields. Large numbers of photographs of the Martian landscape, including surface details of rock, boulders, and soil have been obtained by the ‘Spirit’, ‘Opportunity’, and ‘Curiosity’ rovers. Some of these photographs have been reported to reveal signs of either early fossil life or even of living organisms on the surface including algae, fungi, and lichens. The information which can be obtained from such photographs is often limited, difficult to interpret, and highly controversial. Pattern analysis methods may help to determine whether an observed feature visible on the surface of Mars is evidence of biological origin or the result of a non biological process. This chapter discusses the problems of establishing a scale measure for a quantitative analysis and describes methods of determining spatial pattern, i.e., whether a feature is distributed at random, regularly, or is aggregated into clusters. The pattern analysis methods are illustrated with reference to the analysis of the spatial distribution of two controversial features revealed in Martian photographs, viz. the ‘blueberries’ imaged by the rover Opportunity in Eagle crater and the abundant lozenge-shaped ‘rice-grains’ imaged by Curiosity in Gale crater. The limitations of the various methods and future developments are also discussed.
... The possibility that microbes and stromatolites may have colonized ancient Martian lakes has been advanced earlier based on the spectral response (e.g., [98]) and images of rovers [99,100]. There have been fewer attempts to identify biosignatures on the basis of the morphology seen by satellite images. ...
Mars has held large amounts of running and standing water throughout its history, as evidenced by numerous morphologies attributed to rivers, outflow channels, lakes, and possibly an ocean. This work examines the crater Antoniadi located in the Syrtis Major quadrangle. Some parts of the central area of the crater exhibit giant polygonal mud cracks, typical of endured lake bottom, on top of which a dark, tens of kilometers-long network of dendritic (i.e., arborescent) morphologies emerges, at first resembling the remnant of river networks. The network, which is composed of tabular sub-units, is in relief overlying hardened mud, a puzzling feature that, in principle, could be explained as landscape inversion resulting from stronger erosion of the lake bottom compared to the endured crust of the riverine sediments. However, the polygonal mud cracks have pristine boundaries, which indicate limited erosion. Furthermore, the orientation of part of the network is the opposite of what the flow of water would entail. Further analyses indicate the similarity of the dendrites with controlled diffusion processes rather than with the river network, and the presence of morphologies incompatible with river, alluvial, or underground sapping processes, such as overlapping of branches belonging to different dendrites or growth along fault lines. An alternative explanation worth exploring due to its potential astrobiological importance is that the network is the product of ancient reef-building microbialites on the shallow Antoniadi lake, which enjoyed the fortunate presence of a heat source supplied by the Syrtis Major volcano. The comparison with the terrestrial examples and the dating of the bottom of the crater (formed at 3.8 Ga and subjected to a resurfacing event at 3.6 Ga attributed to the lacustrine drape) contribute to reinforcing (but cannot definitely prove) the scenario of microbialitic origin for dendrites. Thus, the present analysis based on the images available from the orbiters cannot be considered proof of the presence of microbialites in ancient Mars. It is concluded that the Antoniadi crater could be an interesting target for the research of past Martian life in future landing missions.
... Joseph et al 2020d,e,g);Kazmierczak 2016Kazmierczak , 2020Noffke 2015;Rabb, 2018;Rizzo et al. 2020; Ruff & Farmer 2016;Small 2015); (2) biological residue discovered in Martian meteoritesMcKay et al. 2009); (3) living organisms including algae, fungi, and lichens (Dass 2017, Joseph 2014a 2016; Joseph et al. 2019, Joseph et al 2020a,b; Krupa 2017; Levin et al. 1978; Levin & Straat 2016; Rabb 2018, Small 2015); (4) biological activity detected in Martian soil samples ...
There is life on Mars as documented with 100 comparative photos. This evidence includes pigmented/melanized fungi and lichens, fungi shedding crustose and secreting calcium oxalate, fungi preparing to spore, spores on the surface sprouting embryonic mushrooms, fungus growing out of the ground, lichens with hollow stalks, vast colonies of lichens attached to rocks and oriented skyward similar to photosynthesizing lichens on Earth, and documentation that the claims of spherical hematite is a hoax--a byproduct of religious extremism at NASA--which is why the hematite claims were immediately rejected as inappropriate and implausible by a number of investigators who proposed instead they are tektites and accretionary lapilli produced by meteor impact and volcano. Be they on the surface or attached to Martian rocks they have no resemblance to terrestrial hematite. The “spheres” of Mars are uniform in shape and size (1mm or 3mm to 6 mm) and all were initially described as “yellow” “orange” “purple” and “blue” the pigmented colors of photosynthesizing organisms. Terrestrial hematite “spheres” are colored red to dark red, consist of less than 2% hematite which form a thin layer on the surface and have a wide variety of sizes and shapes and are infiltrated by fungi and lichens. A review of the Opportunity teams’ methodology and instrumentation reveals that data was contaminated and confounded by numerous uncontrolled variables including problems with instrument calibrations and they relied on inference, speculation, data manipulation, and spectra from panoramic images that were selectively eliminated in a failed attempt to make it conform to laboratory samples. The iron-rich radiation-intense Red Planet provides an ideal environment for fungus and lichens to flourish and promotes growth and sporing and production of melanin which protects against while simultaneously utilizing radiation for metabolic energy. Algae secrete calcium and lichens and fungi produce calcium oxalate that “weathers” and dissolves minerals and metals which are utilized as nutrients and are stored on cellular surfaces. Terrestrial species are iron-rich and precipitate hematite which makes these fungi and lichens ideal bioindicators of metal and minerals; whereas on Mars they are likely supersaturated with these and other minerals and metals as reflected by spectral data. Fungi and lichens secrete calcium oxalate which coats and surrounds mycelium, but upon exposure to dry surface conditions forms waves of calcium “cement” that may cement these organisms to layers of calcium oxalate fossilizing and making them “harder than rock.” Yet others grow out of the ground and are obviously alive. Given evidence documenting biological residue in Martian meteorites, biological activity in soil samples, seasonal increases in methane and oxygen which parallel biological fluctuations on Earth, and pictorial and quantitative morphological evidence of stromatolites fossilized tube worms and metazoans, growth of mushrooms and fungi, and vast colonies of rock-dwelling lichens, it is concluded that the evidence is obvious: There is life on Mars.
