Snowball Earth: When Ice Reached the Equator
Snowball Earth was a time when our planet may have frozen nearly from pole to pole, testing life and setting the stage for later biological change.
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Our Solar System
Moon Formation
In a cataclysmic event, a Mars-sized object named Theia collided with the early Earth, sending massive amounts of debris into orbit. This debris coalesced over time to form the Moon, which eventually became tidally locked to the Earth, stabilizing the planet’s axis and paving the way for the development of life. The Moon is comprised
Late Heavy Bombardment
Visual Craters of the Moon! In a period known as the Late Heavy Bombardment, the solar system experienced a intense barrage of asteroid and comet impacts, with many large objects striking the Earth and Moon. This event likely occurred as the giant planets Jupiter and Saturn migrated to their current orbits, sending smaller bodies into
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Great Oxidation Event: Third Atmosphere
About 2.4 billion years ago, Cyanobacteria “hacked” the sun to split water, releasing oxygen as a byproduct and triggering the first global environmental catastrophe and subsequent biological reset.
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Second Atmosphere: Carbon Dioxide & Nitrogen
Deep orange or reddish-brown atmosphere: The second atmosphere’s formation was crucial and occurred just before or alongside the formation of Earth’s oceans, which directly supported the evolution of organic molecules and prebiotic microenvironments. The second atmosphere began to develop around 4.5 to 4 billion years ago, as volcanic outgassing released gases trapped in the Earth’s
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First Atmosphere: Hydrogen & Helium
Likely white or grayish atmosphere: The first atmosphere developed first but was not directly involved in the development of life. The first atmosphere formed shortly after Earth’s formation around 4.5 billion years ago. This initial atmosphere was primarily composed of hydrogen and helium, the lightest and most abundant elements in the universe, which were captured from
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First Oceans: Fresh Water
As the Earth cooled following its formation, outgassing from volcanic activity released water vapor and other gases into the atmosphere. When the Earth’s surface cooled sufficiently, this water vapor condensed and fell as rain, filling the basins that would become oceans.
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Second Oceans: From Fresh to Salty
The process of salination likely began soon after the oceans formed but took hundreds of millions of years to reach the salinity levels similar to what we see today. The oceans were likely significantly salty by about 3.5 billion years ago. Salinity increased primarily through the weathering of rocks and the leaching of minerals (including
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Inorganic Precursors to Organic Molecules
The chemical evolution from inorganic precursors to organic molecules is a fascinating story of transformation driven by Earth’s dynamic early conditions and possibly assisted by the input from space in the form of meteorites rich in organic compounds. During this period, the Earth witnessed a series of complex chemical reactions facilitated by its primordial atmosphere,
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Formation of Prebiotic Microenvironments
Alongside or following the chemical evolution of organic molecules, the formation of prebiotic microenvironments, such as hydrothermal vents or warm little ponds, provided niches where concentrations of organic molecules could interact. These environments could have been crucial for the assembly of complex organic molecules and the initiation of catalytic cycles.
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Chemical Evolution of Organic Molecules
While the 4.4 billion years ago is a guess as to when these processes might have started, the 4.1 billion years ago guess is a better representatoin of current understanding on when the needed building blocks of life evolved. Before the appearance of self-replicating molecules, there was a crucial phase of chemical evolution where simple
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Cellular Membranes
The formation of cellular membranes represents a pivotal development in the pre-life world, enabling the creation of defined boundaries for primitive cells. These membranes, likely formed from simple lipid bilayers, provided a controlled environment for chemical reactions and played a critical role in the emergence of the first cell-like structures, distinguishing them from their surrounding
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Earth is Born
The Earth and the other planets formed 4.5 billion years ago from the same cosmic cloud—the primordial material which gave birth to the Sun. The dust and comets—the rocks—were composed largely of hydrogen, ice, carbon, and nitrogen.
Birth of the Sun
4.6 billion years ago, a cloud of gas and dust collapsed under the force of its own gravity to form our solar system.With the Sun at its center, glowing, the planets had not yet formed. The Sun, a G-type Population 1 star, shines brightly with a surface temperature of about 9,400 degrees, 5,500 Kelvin, and
RCW 86 Supernova
This supernova was observed by Chinese astronomers in 185 CE. The Chinese kept meticulous astronomical records for centuries, including observations of what modern scientists interpret as supernovae. Chinese astronomical records from 185 AD describe the appearance of a “guest star” in the constellation now known as Circinus. This guest star matches the expected location and
Oldest Known Fossil-Microorganisms
The earliest known life on Earth are fossilized microorganisms found in hydrothermal vent precipitates. Currently dated to about 3.42 billion BCE. These microorganisms were prokaryote cells. Single celled organisms with no nucleus and had early simple DNA. More complex DNA in a nucleus evolved about 1.5 billion years later in Eukaryotic cells, circa 2 billion
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South America Splits from Africa
Over millions of years, the modern-day South America and Africa separated during the breakup of the supercontinent Pangaea.
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Opening of the North Atlantic Ocean
North America splits from Europe causing diverging evolutionary lines. Over millions of years, the modern-day Europe (Eurasian plate) and North America (North American Plate) separated during the final breakup of Pangaea in the early Cenozoic Era. This split is a later part of that breakup and created the North Atlantic Ocean.
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Plate Tectonics
By dating rocks and fossils scientists can document the movement of the continents over time. To confirm and refine this science, geologists study rocks, paleontologists study fossils, and anthropologists study human societies, cultures, and relics. The location and dating of rocks, fossils, and relics allow us to understand the distant past. Cynognathus, circa 242 million
Pangaea Splitting Starts Splitting Evolution
The breakup of Pangaea did not just reshape geography. It reshaped evolution by isolating populations, limiting movement, and allowing different branches of life to follow different paths.
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