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Conditions on Early Earth

Conditions on Early Earth

Around 4 billion years ago, oceans began to condense on earth while volcanic eruptions released nitrogen, carbon dioxide, methane, ammonia, and hydrogen into the primordial atmosphere. However, organisms with the characteristics of life were not initially present on earth. Scientists have used experimentation to determine how organisms evolved that could grow, reproduce, and maintain an internal environment.

Conditions on Early Earth

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Around 4 billion years ago, oceans began to condense on earth while volcanic eruptions released nitrogen, carbon dioxide, methane, ammonia, and hydrogen into the primordial atmosphere. However, organisms with the characteristics of life were not initially present on earth. Scientists have used experimentation to determine how organisms evolved that could grow, reproduce, and maintain an internal environment.

Eukaryotic Evolution

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The endosymbiont theory is the most widely accepted theory of eukaryotic evolution; however, its progression is still somewhat debated. According to the nucleus-first hypothesis, the ancestral prokaryote first evolved a membrane to enclose DNA and form the nucleus. Conversely, the mitochondria-first hypothesis suggests that the nucleus was formed after endosymbiosis of mitochondria.
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Diversity of Protists I

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Photosynthesis represents a fundamental biological process that transformed Earth's atmosphere and paved the way for complex life. Emerging roughly 3.4–3.8 billion years ago, the earliest photosynthetic organisms harnessed light energy to produce organic compounds. These anoxygenic phototrophs used electron donors like hydrogen sulfide (H₂S) or ferrous iron (Fe²⁺), rather than water, and did not release molecular oxygen (O₂) as a byproduct. Various groups, including green sulfur and purple...

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Related Experiment Video

Updated: Jul 11, 2026

Establishment of Microbial Eukaryotic Enrichment Cultures from a Chemically Stratified Antarctic Lake and Assessment of Carbon Fixation Potential

Establishment of Microbial Eukaryotic Enrichment Cultures from a Chemically Stratified Antarctic Lake and Assessment of Carbon Fixation Potential

Published on: April 20, 2012

Comet or asteroid shower in the late Eocene?

Roald Tagle¹, Philippe Claeys

¹Institut fuer Mineralogie, Museum fuer Naturkunde, D-10099 Berlin, Germany.

Science (New York, N.Y.)

|July 27, 2004

Summary

A comet shower may not explain Earth's Eocene impact events. New platinum-group element analyses suggest an L-chondrite meteorite formed the Popigai crater, challenging the cometary impact hypothesis.

Area of Science:

Planetary Science
Geology
Cosmochemistry

Background:

The late Eocene (approx. 35 million years ago) saw a high influx of interplanetary dust and the formation of two massive impact craters: Popigai and Chesapeake Bay.
A comet shower has been the prevailing theory to explain this coincidence.

Purpose of the Study:

To investigate the projectile type responsible for the Popigai crater.
To re-evaluate the cause of the increased extraterrestrial material flux during the late Eocene.

Main Methods:

Platinum-group element (PGE) analysis of samples from the Popigai impact structure.
Comparison of PGE signatures with known meteorite compositions.

Main Results:

PGE analyses indicate the Popigai crater was formed by an L-chondrite meteorite impact.

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An L-chondrite projectile is inconsistent with a cometary origin.

The high flux of extraterrestrial matter may have a different source.

Conclusions:

The Popigai crater's formation by an L-chondrite meteorite challenges the comet shower hypothesis for late Eocene impact events.
A major collision within the asteroid belt is proposed as a more plausible cause for the increased delivery of extraterrestrial matter, including dust and large impactors.