What was early atmosphere like

Earth is the only object in our solar system known to support life Figure Today there are over 1 million known species of plants and animals on Earth. The materials that came together to form the Earth were made of several different chemical elements. Each element has a different density , defined as mass per volume. Density describes how heavy an object is compared to how much space the object takes up.

The lighter elements rose to the surface. You have probably seen something like this happen if you have ever mixed oil and water in a bottle. The water is denser than oil. If you put both in a bottle, shake it up, and then let it sit for a while, the water settles to the bottom and the oil rises up over the top of the water. Today, the Earth consists of layers that represent different densities Figure The core is made of very dense metal elements called iron and nickel.

The outermost layer of the Earth is its crust. The crust is made mostly of light elements such as silicon, oxygen, and aluminum. More information on the different layers of the Earth is presented in the lesson on plate tectonics.

The center of the Earth is the core, which is the densest. The outermost layer is the crust, which is the least dense. The middle layers make up the mantle. The early Earth experienced frequent impacts from asteroids and meteorites and had much more frequent volcanic eruptions. There was no life on Earth for the first billion years because the atmosphere was not suitable for life.

Later, frequent volcanic eruptions put several different gases into the air Figure These gases created a new type of atmosphere for Earth. The volcanic eruptions spewed gases such as nitrogen, carbon dioxide, hydrogen, and water vapor into the atmosphere—but no free oxygen.

Without oxygen, there was still very little that could live on Earth. The ability to do this was made possible with the development of a new laser furnace technique. For years, geologists have turned to the APS to study the composition of rocks and the oxidation state of the iron contained within them. When the time came for the scientists to have their samples analyzed, there was an obvious place to go.

The beamline he works on can focus its beams to as small as 1 micron across — about 50 times smaller than the width of a human hair — giving scientists the ability to make very precise and accurate measurements of their samples.

In the s, Stanley Miller conducted a groundbreaking experiment at the University of Chicago showing that amino acids — the building blocks of life — would form in an environment with liquid water and air rich in methane and ammonia when zapped with electricity to simulate lightning. At the time, these were the conditions believed to exist on the early Earth. On Earth, liquid water formed out of this magma-made atmosphere, pulling carbon dioxide out of the air and into newly forming oceans.

When that magma nears the surface, those gases are released into the surrounding air. These frozen magmas and the elements they contain can be literal milestones in the history of Earth. One important milestone is zircon. Unlike other materials that are destroyed over time by erosion and subduction, certain zircons are nearly as old as the Earth itself. As such, zircons can literally tell the entire history of the planet — if you know the right questions to ask.

Understanding the level of oxidation could spell the difference between nasty swamp gas and the mixture of water vapor and carbon dioxide we are currently so accustomed to, according to study lead author Dustin Trail, a postdoctoral researcher in the Center for Astrobiology.

Cumulative history of O 2 by photosynthesis through geologic time. The oxygen did not build up in the atmosphere for a long time, since it was absorbed by rocks that could be easily oxidized rusted.

To this day, most of the oxygen produced over time is locked up in the ancient "banded rock" and "red bed" rock formations found in ancient sedimentary rock. The figure illustrates a possible scenario.

We have briefly mentioned the difference between reducing electron-rich and oxidizing electron hungry substances. Oxygen is the most important example of the latter type of substance that led to the term oxidation for the process of transferring electrons from reducing to oxidizing materials. This consideration is important for our discussion of atmospheric evolution, since the oxygen produced by early photosynthesis must have readily combined with any available reducing substance.

It did not have far to look! We have been able to outline the steps in the long drawn out process of producing present-day levels of oxygen in the atmosphere. We refer here to the geological evidence. These ferrous ions were the consequences of millions of years of rock weathering in an anaerobic oxygen-free environment. The first oxygen produced in the oceans by the early prokaryotic cells would have quickly been taken up in oxidizing reactions with dissolved iron.

This oceanic oxidization reaction produces Ferric oxide Fe 2 O 3 that would have deposited in ocean floor sediments. The earliest evidence of this process dates back to the Banded Iron Formations, which reach a peak occurrence in metamorphosed sedimentary rock at least 3. Most of the major economic deposits of iron ore are from Banded Iron formations. These formations, were created as sediments in ancient oceans and are found in rocks in the range 2 - 3. Very few banded iron formations have been found with more recent dates, suggesting that the continued production of oxygen had finally exhausted the capability of the dissolved iron ions reservoir.

At this point another process started to take up the available oxygen. Red Beds Once the ocean reservoir had been exhausted, the newly created oxygen found another large reservoir - reduced minerals available on the barren land. Oxidization of reduced minerals, such as pyrite FeS 2 , exposed on land would transfer oxidized substances to rivers and out to the oceans via river flow.

Deposits of Fe 2 O 3 that are found in alternating layers with other sediments of land origin are known as Red Beds, and are found to date from 2. The earliest occurrence of red beds is roughly simultaneous with the disappearance of the banded iron formation, further evidence that the oceans were cleared of reduced metals before O 2 began to diffuse into the atmosphere. Finally after another 1. This signal event initiated eukaryotic cell development, land colonization, and species diversification.

Perhaps this period rivals differentiation as the most important event in Earth history. The oxygen built up to today's value only after the colonization of land by green plants, leading to efficient and ubiquitous photosynthesis. The Oxygen Concentration Problem. This is not a trivial question since significantly lower or higher levels would be damaging to life.

The Early Ultraviolet Problem The genetic materials of cells DNA is highly susceptible to damage by ultraviolet light at wavelengths near 0.

It is estimated that typical contemporary microorganisms would be killed in a matter of seconds if exposed to the full intensity of solar radiation at these wavelength. Today, of course, such organisms are protected by the atmospheric ozone layer that effectively absorbs light at these short wavelengths, but what happened in the early Earth prior to the significant production of atmospheric oxygen?

There is no problem for the original non-photosynthetic microorganisms that could quite happily have lived in the deep ocean and in muds, well hidden from sunlight. But for the early photosynthetic prokaryotes, it must have been a matter of life and death. It is a classical "chicken and egg" problem.