◾ Fossil Records for Early Life on Earth

Astrobiology ◽  
2014 ◽  
pp. 188-223
Keyword(s):  
Early Life ◽  
Fossil Records ◽  
Life On Earth

3.43 billion-year-old stromatolite reef from the Pilbara Craton of Western Australia: Ecosystem-scale insights to early life on Earth

2007 ◽  
Vol 158 (3-4) ◽  
pp. 198-227 ◽  
Author(s):  
Abigail C. Allwood ◽  
Malcolm R. Walter ◽  
Ian W. Burch ◽  
Balz S. Kamber
Keyword(s):  
Western Australia ◽  
Early Life ◽  
Life On Earth ◽  
Pilbara Craton

scholarly journals Volcaniclastic habitats for early life on Earth and Mars: A case study from ∼3.5Ga-old rocks from the Pilbara, Australia

2011 ◽  
Vol 59 (10) ◽  
pp. 1093-1106 ◽  
Author(s):  
Frances Westall ◽  
Frédéric Foucher ◽  
Barbara Cavalazzi ◽  
Sjoukje T. de Vries ◽  
Wouter Nijman ◽  
...  
Keyword(s):  
Early Life ◽  
Life On Earth

A symbiotic view of the origin of life at hydrothermal impact crater-lakes

2016 ◽  
Vol 18 (30) ◽  
pp. 20033-20046 ◽  
Author(s):  
Sankar Chatterjee
Keyword(s):  
Origin Of Life ◽  
Early Life ◽  
Hydrothermal Vents ◽  
Impact Crater ◽  
Crater Lakes ◽  
Origin And Evolution ◽  
The Origin Of Life ◽  
Life On Earth

Submarine hydrothermal vents are generally considered as the likely habitats for the origin and evolution of early life on Earth.

Mineral remains of early life on earth? On mars?

1991 ◽  
Vol 9 (1) ◽  
pp. 51-66 ◽  
Author(s):  
Eleanora Iberall Robbins ◽  
Arthur S. Iberall
Keyword(s):  
Early Life ◽  
Life On Earth

scholarly journals Organic biomorphs may be better preserved than microorganisms in early Earth sediments

Geology ◽  
2021 ◽  
Author(s):  
Christine Nims ◽  
Julia Lafond ◽  
Julien Alleon ◽  
Alexis S. Templeton ◽  
Julie Cosmidis
Keyword(s):  
Early Life ◽  
Colloidal Silica ◽  
Early Earth ◽  
Correct Identification ◽  
Precambrian Rock ◽  
Geochemical Conditions ◽  
Organic Composition ◽  
Siliceous Rocks ◽  
Rock Record ◽  
Life On Earth

The Precambrian rock record contains numerous examples of microscopic organic filaments and spheres, commonly interpreted as fossil microorganisms. Microfossils are among the oldest traces of life on Earth, making their correct identification crucial to our understanding of early evolution. Yet, spherical and filamentous microscopic objects composed of organic carbon and sulfur can form in the abiogenic reaction of sulfide with organic compounds. Termed organic biomorphs, these objects form under geochemical conditions relevant to the sulfidic environments of early Earth. Furthermore, they adopt a diversity of morphologies that closely mimic a number of microfossil examples from the Precambrian record. Here, we tested the potential for organic biomorphs to be preserved in cherts; i.e., siliceous rocks hosting abundant microbial fossils. We performed experimental silicification of the biomorphs along with the sulfur bacterium Thiothrix. We show that the original morphologies of the biomorphs are well preserved through encrustation by nano-colloidal silica, while the shapes of Thiothrix cells degrade. Sulfur diffuses from the interior of both biomorphs and Thiothrix during silicification, leaving behind empty organic envelopes. Although the organic composition of the biomorphs differs from that of Thiothrix cells, both types of objects present similar nitrogen/carbon ratios after silicification. During silicification, sulfur accumulates along the organic envelopes of the biomorphs, which may promote sulfurization and preservation through diagenesis. Organic biomorphs possessing morphological and chemical characteristics of microfossils may thus be an important component in Precambrian cherts, challenging our understanding of the early life record.

The sabkhas of Qatar: modern analogues for studying early life on Earth and on Mars

2020 ◽  
Author(s):  
Tomaso Bontognali ◽  
Franziska Blattmann ◽  
Zulfa Al Disi ◽  
Hamad Al Saad Al Kuwari ◽  
Zach DiLoreto ◽  
...  
Keyword(s):  
Early Life ◽  
Extracellular Polymeric Substances ◽  
Microbial Mats ◽  
Natural Environments ◽  
Intertidal Zones ◽  
Anoxygenic Phototrophs ◽  
Nucleation Sites ◽  
Uppermost Layer ◽  
Upper Intertidal ◽  
Life On Earth

<p>The study of early life on Earth and the search for life on Mars often includes investigations of modern analogues: natural environments that share similarities to what we hypothesize may have existed on the early Earth and early Mars. The study of modern analogues provides key information on how biosignatures are formed and preserved, which is essential for interpreting the geological record. Research conducted in recent years in various modern sabkhas located along the coast of Qatar have demonstrated that these extreme evaporitic environments represent an inspirational gold mine for the field of geobiology and astrobiology.</p><p>The intertidal zones of the Qatari sabkhas are typically colonized by microbial mats. Their presence leads to the formation of Microbially Influenced Sedimentary Structures (MISS). Examples of studied MISS include polygonal, domical, blistered, tufted and crinkled microbial mats. We discuss biological vs. physiochemical factors responsible for their formation, as well as their fossilization potential. These MISS often occur in a precise sequence along a transect from the lower to the upper intertidal zone. We propose that a MISS sequence represents a stronger morphological biosignature than a single MISS. The community composition of some of the studied mats revealed an uppermost layer dominated by anoxygenic phototrophs. We propose that such mats represent a particularly good analogue for studying life in the Early Archean, a time when the cyanobacteria that usually dominate the uppermost photo-oxic layer of most modern mats probably did not exist.</p><p>Besides influencing sediment morphology, the extracellular polymeric substances (EPS) constituting the mats serve as nucleation sites for the precipitation of authigenic minerals. Among these possible precipitates, our research focused on microbially influenced Mg-rich carbonates and Mg-rich silicates. Linking these minerals to a microbial process is of particular interest in view of the forthcoming rover missions to Mars (i.e., ExoMars and Mars 2020). Indeed, orbital spectral analyses revealed the presence of Mg-rich clays and Mg-rich carbonates in the surroundings of the proposed landing sites. It will be exciting to test the hypothesis that, on Mars, some of these minerals may have formed at low temperatures from liquid water and may, therefore, represent a target phase for the investigation of biosignatures.</p>

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