The ~1.6 Ga Tirohan Dolomite of the Lower Vindhyan in central India contains phosphatized stromatolitic microbialites. We report from there uniquely well-preserved fossils interpreted as probable crown-group rhodophytes (red algae). The filamentous form Rafatazmia chitrakootensis n. gen, n. sp. has uniserial rows of large cells and grows through diffusely distributed septation. Each cell has a centrally suspended, conspicuous rhomboidal disk interpreted as a pyrenoid. The septa between the cells have central structures that may represent pit connections and pit plugs. Another filamentous form, Denaricion mendax n. gen., n. sp., has coin-like cells reminiscent of those in large sulfur-oxidizing bacteria but much more recalcitrant than the liquid-vacuole-filled cells of the latter. There are also resemblances with oscillatoriacean cyanobacteria, although cell volumes in the latter are much smaller. The wider affinities of Denaricion are uncertain. Ramathallus lobatus n. gen., n. sp. is a lobate sessile alga with pseudoparenchymatous thallus, “cell fountains,” and apical growth, suggesting florideophycean affinity. If these inferences are correct, Rafatazmia and Ramathallus represent crown-group multicellular rhodophytes, antedating the oldest previously accepted red alga in the fossil record by about 400 million years.

Fossil microbiotas are rare in the early rock record, limiting the type of ecological information extractable from ancient microbialites. In the absence of body fossils, emphasis may instead be given to microbially derived features, such as microbialite growth patterns, microbial mat morphologies, and the presence of fossilized gas bubbles in lithified mats. The metabolic affinity of micro-organisms associated with phosphatization may reveal important clues to the nature and accretion of apatite-rich microbialites. Stromatolites from the 1.6 Ga Chitrakoot Formation (Semri Group, Vindhyan Supergroup) in central India contain abundant fossilized bubbles interspersed within fine-grained in situ-precipitated apatite mats with average δ C indicative of carbon fixation by the Calvin cycle. In addition, the mats hold a synsedimentary fossil biota characteristic of cyanobacterial and rhodophyte morphotypes. Phosphatic oncoid cone-like stromatolites from the Paleoproterozoic Aravalli Supergroup (Jhamarkotra Formation) comprise abundant mineralized bubbles enmeshed within tufted filamentous mat fabrics. Construction of these tufts is considered to be the result of filamentous bacteria gliding within microbial mats, and as fossilized bubbles within pristine mat laminae can be used as a proxy for oxygenic phototrophy, this provides a strong indication for cyanobacterial activity in the Aravalli mounds. We suggest that the activity of oxygenic phototrophs may have been significant for the formation of apatite in both Vindhyan and Aravalli stromatolites, mainly by concentrating phosphate and creating steep diurnal redox gradients within mat pore spaces, promoting apatite precipitation. The presence in the Indian stromatolites of alternating apatite-carbonate lamina may result from local variations in pH and oxygen levels caused by photosynthesis-respiration in the mats. Altogether, this study presents new insights into the ecology of ancient phosphatic stromatolites and warrants further exploration into the role of oxygen-producing biotas in the formation of Paleoproterozoic shallow-basin phosphorites.

A growing awareness of life in deep igneous crust expands our appreciation for life's distribution in the upper geosphere through time and space, and extends the known inhabitable realm of Earth and possibly beyond. For most of life's history, until plants colonized land in the Ordovician, the deep biosphere was the largest reservoir of living biomass. This suggests that deep crustal habitats played an important role in the evolution and development of the biosphere. Paradoxically, the paleo-perspective of deep life has been largely neglected in the exploration of the deep biosphere as well as in paleontology as a whole. Here, we review the collective understanding of the fossil record in igneous crust with the aim to highlight a rising research field with great potential for substantial findings and progress in the near future. We include new results that emphasize the importance of direct or indirect dating of fossils and introduction of new techniques into the field. Currently, an incoherent record of morphological fossils-and chemofossils stretching from present to~2.4 Ga implies the presence of an abundant and rich, yet largely unexplored, fossil record. Further investigations of deep paleo-environments will most certainly result in substantial insights into the distribution and development of biospheres throughout life's history, the early evolution of prokaryotes and eukaryotes, and Earth's early biogeochemical cycles. We emphasize the fossil record of igneous rock to give it the same status as the fossil record in sedimentary rocks, and to implement fossil investigations as standard procedures in future international drilling campaigns.

Lim et al. spe 483-01 page 86 bodies where scientifi c investigation is a key driver of exploration. In order to explore and collect samples underwater at Pavilion Lake, humans must, as they do in space, coordinate with unmanned robotic systems and contend with limitations associated with communications, visualization, and sampling of their environments, and their life support systems (LSS) (Lim et al., 2010). These working constraints are not simulated, but are real and inextricable from the PLRP's activities. As such, Pavilion Lake has become an important analog research environment in which to garner operational information applicable to the design of human planetary exploration strategies. The goal of this paper is to present a historical synopsis of analog science and exploration activities at Pavilion Lake with the specifi c aim of highlighting the unique contributions of the PLRP to the development of human planetary exploration strategies. To ensure that the complexity and richness of the project are properly captured in this paper, two appendices are included that document some of the PLRP's additional initiatives and activities (e.g., education and public outreach).

Speleothems are secondary mineral deposits normally formed by water supersaturated with calcium carbonate percolating into underground caves, and are often associated with low-nutrient and mostly non-phototrophic conditions. Tjuv-Ante’s cave is a shallow-depth cave formed by the action of waves, with granite and dolerite as major components, and opal-A and calcite as part of the speleothems, making it a rare kind of cave. We generated two DNA shotgun sequencing metagenomic datasets from the interior of a speleothem from Tjuv-Ante’s cave representing areas of old and relatively recent speleothem formation. We used these datasets to perform i) an evaluation of the use of these speleothems as past biodiversity archives, ii) functional and taxonomic profiling of the speleothem’s different formation periods, and iii) taxonomic comparison of the metagenomic results to previous microscopic analyses from a nearby speleothem of the same cave. Our analyses confirm the abundance of Actinobacteria and fungi as previously reported by microscopic analyses on this cave, however we also discovered a larger biodiversity. Interestingly, we identified photosynthetic genes, as well as genes related to iron and sulphur metabolism, suggesting the presence of chemoautotrophs. Furthermore, we identified taxa and functions related to biomineralization. However, we could not confidently establish the use of this type of speleothems as biological paleoarchives due to the potential leaching from the outside of the cave and the DNA damage that we propose has been caused by the fungal chemical etching.

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Rock-inhabiting fungi harbour species-rich, poorly differentiated, extremophilic taxa of polyphyletic origin. Their closest relatives are often well-known species from various biotopes with significant pathogenic potential. Speleothems represent a unique rock-dwelling habitat, whose mycobiota are largely unexplored. Isolation of fungi from speleothem biofilm covering bare granite walls in the Kungsträdgården metro station in Stockholm yielded axenic cultures of two distinct black yeast morphotypes. Phylogenetic analyses of DNA sequences from six nuclear loci, ITS, nuc18S and nuc28S rDNA, rpb1, rpb2 and β-tubulin, support their placement in the Chaetothyriales (Ascomycota). They are described as a new genus Bacillicladium with the type species B. lobatum, and a new species Bradymyces graniticola. Bacillicladium is distantly related to the known five chaetothyrialean families and is unique in the Chaetothyriales by variable morphology showing hyphal, meristematic and yeast-like growth in vitro. The nearest relatives of Bacillicladium are recruited among fungi isolated from cardboard-like construction material produced by arboricolous non-attine ants. Their sister relationship is weakly supported by the Maximum likelihood analysis, but strongly supported by Bayesian inference. The genus Bradymyces is placed amidst members of the Trichomeriaceae and is ecologically undefined; it includes an opportunistic animal pathogen while two other species inhabit rock surfaces. ITS rDNA sequences of three species accepted in Bradymyces and other undescribed species and environmental samples were subjected to phylogenetic analysis and in-depth comparative analysis of ITS1 and ITS2 secondary structures in order to study their intraspecific variability. Compensatory base change criterion in the ITS2 secondary structure supported delimitation of species in Bradymyces, which manifest a limited number of phenotypic features useful for species recognition. The role of fungi in the speleothem biofilm and relationships of Bacillicladium and Bradymyces with other members of the Chaetothyriales are discussed.

The exploration of Mars is largely based on comparisons with Earth analog environments and processes. The up-coming NASA Mars mission 2020 and ExoMars 2020 has the explicit aim to search for signs of life on Mars. During preparations for the missions, glaring gaps in one specific field was pointed out: the lack of a fossil record in igneous and volcanic rock. Earth's fossil record is almost exclusively based on findings in sedimentary rocks, while igneous rocks have been considered barren of life, including a fossil record of past life. Since martian volcanic rocks will be targeted in the search for biosignatures, the lack of a terrestrial analog fossil record is an obvious impediment to the scientific aim of the mission. Here we will briefly review the knowledge of microscopic life in deep rock and deep time. Focus will be on underexplored environments in subseafloor crustal rocks, and on ancient environments harboring early prokaryotic and eukaryotic lineages. We will highlight some of the aspects that need immediate attention and further investigations to meet the scientific goals of the missions. The current paper is a first step toward the long-term aim to establish an atlas of the fossil record in volcanic rocks, which can be of use for the up-coming space missions.