The earliest evidence for life on Earth arises among the oldest rocks still preserved on the planet. Earth is about 4.5 billion years old, but the oldest rocks still in existence date back to just 4 billion years ago. Not long after that rock record begins, tantalizing evidence of life emerges: A set of filament-like fossils from Australia, reported in the journal Astrobiology in 2013, may be the remains of a microbial mat that might have been extracting energy from sunlight some 3.5 billion years ago. Another contender for world's oldest life is a set of rocks in Greenland that may hold the fossils of 3.7-billion-year-old colonies of cyanobacteria, which form layered structures called stromatolites. Some scientists have claimed to see evidence of life in 3.8-billion-year-old rocks from Akilia Island, Greenland. The researchers first reported in 1996 in the journal Nature that isotopes (forms of an element with different numbers of neutrons) in those rocks might indicate ancient metabolic activity by some mystery microbe. Those findings have been hotly debated ever since — as, in fact, have all claims of early life. Most recently, scientists reported in the journal Nature that they had discovered microfossils in Canada that might be between 3.77 billion and 4.29 billion years old, a claim that would push the origins of life to very shortly after Earth first formed oceans. The filament-like fossils contained chemical signals that could herald life, but it's hard to prove that they do, researchers not involved in the study told Live Science. It's also hard to prove that fossils found in ancient rocks are necessarily ancient themselves; fluids have penetrated cracks in the rock and might have allowed newer microbes in to older rock. The researchers used samarium-neodymium dating to arrive at the 4.29 billion maximum age for the fossils. This method, which uses the decay of one rare-earth element into another, may measure the age of the magma that formed the rocks rather than the rocks themselves, an issue that has also dogged claims of the Earth's oldest rocks (opens in new tab). Still, the fact that suggestive evidence of life arises right as the rock record begins raises a question, said University of California, Los Angeles, geochemist Elizabeth Bell in a SETI Talk in February 2016: Is the timing a coincidence, or were there earlier forms of life whose remnants disappeared with the planet's most ancient rocks?  The period that occurred before the rock record begins is known as the Hadean. It was an extreme time, when asteroids and meteorites pummeled the planet. Bell and her colleagues said they might have evidence that life arose during this very unpleasant time. In 2015, the research team reported discovering graphite, a form of carbon, in 4.1-billion-year-old crystals of zircon. The ratio of isotopes in the graphite suggested a biological origin, Bell and her colleagues wrote in the journal Proceedings of the National Academy of Sciences. "There is some skepticism, which is warranted," Bell told Live Science. Meteorites or chemical processes might have caused the odd carbon ratios, she said, so the isotopes alone aren't proof of life. Since the publication of the 2015 paper, Bell said, the researchers have found several more of the rare-carbon inclusions, which the scientists hope to analyze soon. From what is known of this period, there would have been liquid water on the planet, Bell told Live Science in an interview. There might have been granite, continental-like crust, though that's controversial, she said. Any life that could have existed would have been a prokaryote (a single-celled organism without membrane-bound nuclei or cell organelles), Bell added. If there was continental crust on Earth at the time, she said, prokaryotes might have had mineral sources of nutrients like phosphorus. A different approach to the hunt for Earth's early life suggests that oceanic hydrothermal vents may have hosted the first living things. In a paper published in July 2016 in the journal Nature Microbiology (opens in new tab), researchers analyzed prokaryotes to find the proteins and genes common to all of these organisms, presumably the final remnants of the Last Universal Common Ancestor (LUCA) — the first shared relative from which all life today descends. The research team found 355 proteins shared by all archaeal and bacterial lineages. Based on those proteins, the researchers reconstructed a view of LUCA's genome, hinting that it lived in an anaerobic (oxygen-free), hydrothermal environment. If that's the case, Earth's first life (or at least the first life that left descendants) would have resembled the microbes that cluster around deep-sea vents today, the researchers said. Original article on Live Science. This show captivated me from the very first moment. The photographers are emotionally invested in the animals they're covering while also being aware that the very animal they're so captivated by may die at any moment. Also, their love/interest/concern (call it what you will) for the newborn is contagious and you begin to root for the animals as well. I've just finished the first episode, so can't say anything beyond that, but so far, it's a 10+ in my book! Page 2Earth is estimated to be 4.54 billion years old, plus or minus about 50 million years. Scientists have scoured the Earth searching for the oldest rocks to radiometrically date. In northwestern Canada, they discovered rocks about 4.03 billion years old. Then, in Australia, they discovered minerals about 4.3 billion years old. Researchers know that rocks are continuously recycling, due to the rock cycle, so they continued to search for data elsewhere. Since it is thought the bodies in the solar system may have formed at similar times, scientists analyzed moon rocks collected during the moon landing and even meteorites that have crash-landed on Earth. Both of these materials dated to between 4.4 and 4.5 billion years. Learn more about the age of our planet with these resources. Subjects Earth Science, Geology The early Earth is loosely defined as Earth in its first one billion years, or gigayear (Ga, 109y).[1] The “early Earth” encompasses approximately the first gigayear in the evolution of our planet, from its initial formation in the young Solar System at about 4.55 Ga to sometime in the Archean eon at about 3.5 Ga.[2] On the geologic time scale, this comprises all of the Hadean eon (starting with the formation of the Earth about 4.6 billion years ago[3]), as well as the Eoarchean (starting 4 billion years ago) and part of the Paleoarchean (starting 3.6 billion years ago) eras of the Archean eon.
This period of Earth's history involved the planet's formation from the solar nebula via a process known as accretion. This time period included intense meteorite bombardment as well as giant impacts, including the Moon-forming impact, which resulted in a series of magma oceans and episodes of core formation.[4] After formation of the core, delivery of meteoritic or cometary material in a "late veneer" may have delivered water and other volatile compounds to the Earth.[5] Although little crustal material from this period survives, the oldest dated specimen is a zircon mineral of 4.404 ± 0.008 Ga enclosed in a metamorphosed sandstone conglomerate in the Jack Hills of the Narryer Gneiss Terrane of Western Australia.[6] The earliest supracrustals (such as the Isua greenstone belt) date from the latter half of this period, about 3.8 gya, around the same time as peak Late Heavy Bombardment.
According to evidence from radiometric dating and other sources, Earth formed about 4.54 billion years ago.[7][8][9] Within its first billion years,[10] life appeared in its oceans and began to affect its atmosphere and surface, promoting the proliferation of aerobic as well as anaerobic organisms. Since then, the combination of Earth's distance from the Sun, its physical properties and its geological history have allowed life to emerge, develop photosynthesis, and, later, evolve further and thrive. The earliest life on Earth arose at least 3.5 billion years ago.[11][12][13] Earlier possible evidence of life includes graphite, which may have a biogenic origin, in 3.7-billion-year-old metasedimentary rocks discovered in southwestern Greenland[14] and 4.1-billion-year-old zircon grains in Western Australia.[15][16] In November 2020, an international team of scientists reported studies suggesting that the primeval atmosphere of the early Earth was very different from the conditions used in the Miller–Urey studies considering the origin of life on Earth.[17]
Early Earth - pale orange dot
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What is the first year on earth
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