Properties of the Atmosphere

Without the ozone layer

, living things on Earth would be harmed by ultraviolet (UV) radiation

What do green plants then give back to the atmosphere that makes all animal life on Earth possible?

-Humans, and all other animals, breathe out air and carbon dioxide. -That carbon dioxide is taken up by plants, algae, and photosynthesizing bacteria, which then convert it to organic compounds and give off oxygen as a byproduct. - That oxygen, which is vital for all animal life; is then taken in by humans and other animals, and the cycle begins all over again.

True or False: Earth's atmosphere was very oxygen rich by the beginning of the Archean Eon.

. False Feedback: Earth's atmosphere was not very oxy gen rich until the end of the Proterozoic Eon

The Ozone Layer

. It is found in a layer in the upper part of Earth's atmosphere and reflects significant amounts of harmful solar radiation away from Earth and back to outer space

True or False: Earth's atmosphere during the Hadean was dominated by water vapor and carbon dioxide.

. True Feedback: Earth's early atmosphere was made mostly of carbon dioxide and water vapor from volcanic outgassing.

The Greenhouse Effect

A greenhouse effect is the heating of the planet due to atmospheric gases that absorb radiation.

Stratosphere

Above the troposphere is the stratosphere. This layer is heated by the Sun's UV rays and gets warmer as it goes higher. The stratosphere contains the ozone layer. Ozone molecules absorb high-energy UV from the Sun and make life on Earth possible. Without the protection of the ozone layer, too much radiation would reach Earth's surface. Some human activities release chemical substances called CFC's that can destroy the ozone layer.

Earth's life-support system

Along with water, mineral nutrients, and living things, air is a vital part

Why is atmospheric ozone not a pollutant?

Atmospheric ozone protects Earth from excessive levels of harmful UV radiation.

Which gases contribute most to Earth's greenhouse effect? How does human activity impact the levels of those gases?

Carbon dioxide and methane are two greenhouse gases, both of which are elevated in the atmosphere by burning fossil fuels, by agriculture, and deforestation.

Water vapor

Depending on environmental conditions, water vapor is another trace gas that is in Earth's atmosphere, but its relative concentration can vary from almost zero to four percent. Humidity is a measure of the amount of water vapor in the air at any given time. This value varies from place to place, and with air temperature, season of the year, and daily weather conditions. Warm air can hold more water vapor than cool air, because lower temperatures encourage condensation, or the phase change of gaseous water to liquid water. Regions of higher humidity tend to form over large bodies of water and densely forested regions because of evaporation (the phase change of liquid water to gaseous water) at Earth's surface. The driest air is generally found in the cold Polar regions. The condensation of water vapor is responsible for clouds, rain, snow, and other precipitation on Earth. Water vapor cycles on Earth—that which is lost by precipitation is replenished by evaporation of liquid water from the oceans and seas

As far as we know

Earth is the only planet that supports life.

Earth

Earth is the only planet with an oxygen-rich atmo sphere and the only planet to support life, as far as we know.

True or False: Once free oxygen accumulated in the atmosphere, the oz one layer was destroyed, allowing life outside of the oceans

False Feedback: Accumulations of free oxygen in the atmosphere allowed the development of the ozone layer.

True or False: Earth's second atmosp here was made mostly of nitrogen and methane

False Feedback: Earth's second atmosphere was made mostly of water vapor, with smaller amounts of carbon dioxide and methane. These gases came from outgassing from volcanoes.

True or False: Once photosynthesis began, free oxygen began accumulating at high levels immediately in the atmosphere

False Feedback: Free oxygen first began to combine with iron in the oceans; once all the iron had been reacted, then oxygen began building up in the atmosphere.

True or False: Photosynthesis was important to th e evolution of Earth's atmosphere because it led to increased carbon dioxide.

False Feedback: Photosynthesis gives off oxygen and consumes carbon dioxide. It led to an increase in oxygen and a decrease in carbon dioxide.

True or False: Stromatolites began photos ynthesis on Earth about 3.5 billion years ago.

False Feedback: Stromatolites first em erged about 2.7 billion years ago.

The Greenhouse Effect

However, excessive amounts of carbon dioxide and methane in the atmosphere can result in an enhanced greenhouse effect, making the planet too warm

The Greenhouse Effect

Huma n activities, such as burning fossil fuels, forest fires, deforestation, and agriculture, contribute elev ated levels of carbon dioxide and methane to the atmosphere

We often say that Earth has the "just right" amount of oxygen. Why is this so?

If Earth had any less oxygen, the planet could not support animal metabolism, since oxygen is an essential component of the red blood cells, and necessary for metabolic functioning. If Earth had just five percent more oxygen, then combustion would take place too easily and organic materials would burn.

The Greenhouse Effect

In the absence of any greenhouse effect, Earth would be much t oo cold to sustain life

Thermosphere

In the thermosphere, temperature increases with height. This is the location of the beautiful Aurora Borealis that occurs in the night time sky at northern latitudes. The thermosphere is characterized by the presence of charged particles called ions causing the beautiful Aurora Borealis. It is also where the International Space Station (ISS) orbits.

Jupiter

Jupiter's atmosphere is made almost entirely of the gases, hydrogen and helium. Its outermost atmosphere also contains frozen crystals of ammonia.

Mercury

Mercury is too small for its gravity to hold on to any appreciable atmosphere. There are a few trace levels of light gases such as helium and hydr ogen, but overall Mercury is not considered to have a real atmosphere.

Neptune

Neptune's atmosphere is made up of hydroge n and helium, and considerable amounts of water ice and methane ice. Unlike Uranus, Neptune ha s noticeable weather patterns driven by the strongest winds of any planet in the solar sy stem. Winds on Neptune can reach 2,100 km/hour.

The Greenhouse Effect

On Earth, these gases are primarily carbon dioxi de and methane. They trap heat and keep the planet from getting too cold

. If Earth had any less, there would not be sufficient oxygen to support animal metabolism

On the other hand, if Earth had just five percent more oxygen, then life could not exist because organic materials would burn too easily, wiping them out completely.

All that carbon dioxide also traps heat from the Sun and makes the surface of Venus a rather sweltering 470°C

On top of that, the clouds that swirl over Venus are made of sulfuric acid, and a light drizzle of acid rains over the whole planet

ozone

Ozone at the ground-level is considered an undesirable pollutant. However, in the upper atmosphere, ozone is necessary for life on Earth.

The Ozone Layer

Ozone is a compound of oxygen.

Particulate Matter

Particulate matter is made of tiny solid particles or liquid droplets suspended in air. Particulates can include dust, pollen, and volcanic ash, and can come from natural sources, such as volcanoes, dust storms, or forest fires. They may also come from human-made sources, such as pollution from a factory or vehicle emissions. Elemental mercury is one particulate that comes from industrial emissions and is considered a serious air pollutant. You will learn about air pollution and the effects of particulates later in this unit, but for now, know that increased levels of particulates in the atmosphere are related to serious health threats. Pollution can become trapped in the lungs and particulates can scatter incoming solar radiation, resulting in decreased solar radiation making it to Earth's surface.

Pluto

Pluto's atmosphere is a thin layer of nitrogen, methane, and carbon monoxide. When Pluto is at its farthest point away from the Sun in its orbi t, its atmosphere actually freezes and falls to the ground. As Pluto gets closer to the Sun, the atmosphere changes back to a gas, but temperatures on the planet still get as cold as about -382° F.

Saturn

Saturn's atmosphere is almost entirely made of hydrogen and helium. It has thick cloud cover and very fast winds that reach speeds of up to 1,800 km/hour

Gases

The atmosphere is mostly a mixture of the gases you see here. The pie graphs show the major and minor gases in Earth's atmosphere. In the top graph, you see the major gases of nitrogen (N2), oxygen (O2) and argon (Ar). In the bottom graph, you see the minor, or trace gases, of carbon dioxide (CO2), neon (Ne), helium (He), methane (CH4), hydrogen (H2) and krypton (Kr). Pie charts showing the relative concentrations of major and minor gases in Earth's atmosphere

Uranus

The atmosphere of Uranus is very similar to that of Jupiter and Saturn. It is made mostly of hydrogen and helium. Uranus also has significant levels of water ice, ammonia ice, and methane ice in its atmosphere.

Mars

The atmosphere on Mars is extremely high in ca rbon dioxide gas. But unlike Venus, Mars has a very thin atmosphere, so even though it has high carbon dioxide content, Mars cannot store heat from the Sun. Mars also has a very dusty atmo sphere with a high concentration of particulate matter.

Exosphere

The exosphere is the upper layer of the atmosphere, where particles and gases escape to space. It is the last layer before space, though there is no clear boundary between this layer and outer space. It is sometimes simply called outer space. In this layer, particles are so far apart that they can travel hundreds of kilometers without colliding.

Troposphere

The troposphere is the lowest level of the atmosphere and it is where all weather occurs on Earth. It is heated by heat that radiates from Earth's surface. In the troposphere, temperature decreases as altitude increases.

The Greenhouse Effect

These activities and the resulting gases need to be kept at moderate levels. But at this point in human history, we may be contributing too many greenhouse gases to the atmosphere and creating the phenomenon called global warming.

Earth's atmosphere has three main features that make it unique among the planets and that make life on Earth possible.

These features are significant oxygen levels, a protective ozone layer, and a moderate greenhouse effect.

Mesosphere

This layer is just above the stratosphere. In the mesosphere, temperature decreases with height. This is where meteors burn up when entering the atmosphere. This layer is the coldest place on Earth.

True or False: Over geologic time, Earth's atmosphere evolved from a water vapor and carbon dioxide rich atmosphere to an oxygen-rich atmosphere

True Feedback: Earth's earliest atmosphere was from volcani c gases like water vapor and carbon dioxide; later it evolved into an oxygen-rich atmosphere

True or False: The second atmosphere on Earth developed from gases that came from volcanoes and outgassing of Earth's interior.

True Feedback: Earth's second atmosphere was made mostly of water vapor, with smaller amounts of carbon dioxide and methane. These gases came from outgassing from volcanoes

True or False: Reaction of water vapor with ultraviolet light was the first means of free oxygen becoming available on Earth.

True Feedback: Water vapor in Earth's early atmosphere wa s attacked by ultraviolet light and broken down into free oxygen and hydrogen.

Of the three types of UV radiation

UV-A, UV-B, and UV-C - the ozone layer is most effective at filtering out UV-C

Venus

Venus has the densest atmosphere of all the i nner planets. Its atmosphere is made up almost entirely of carbon dioxide gas, which traps solar radiation and makes Venus the hottest planet in the solar system, with a surfac e temperature of about 860°F.

The Greenhouse Effect

You can see in the diagram th at some solar radiation is reflected back to space, but some of it is absorbed by the greenhou se gases in the atmosphere

Because of Earth's oxygen-rich atmosphere

all animal life on Earth, including human life, is able to exist

Earth's atmosphere and the living things on this planet

are interconnected

. Besides nitrogen and oxygen, what is t he other major gas in Earth's atmosphere?

argon

It is necessary for all of our metabolic functions

but oxygen is only about 21 percent of the air that we breathe in

Oxygen is an essential component

component of our red blood cells and is circulated throughout our bodies, allowing for metabolic function.

What is the process that changes gaseous water to liquid water?

condensation

What is the phase change from a liquid to a gas?

evaporation

picture of outer space

exosphere

What is the measure of the amount of water vapor in the air at any given time?

humidity

The number one way you interact with the atmosphere

is by breathing air.

The component of air that is the most important to your body

is oxygen.

One way interconnection takes place

is through the process of photosynthesis

. Earth's atmosphere is nearly 21% oxygen

just the right amount to support life

picture of a meteor coming toward Earth

mesosphere

What is the most abundant gas in Earth's atmosphere?

nitrogen

Without Earth's unique oxygen-rich atmosphere

nothing could live on Earth.

The atmosphere is a mixture

of gases, water vapor, and particulate matter

. Oxygen is an essential component

of the red blood cells in our bodies

Which gas is present in Earth's atmosphere at about 21 percent concentration?

oxygen

What is the component of the atmosphere that is made up of tiny, solid particles and liquid droplets?

particulate matter

. During this process

plants use sunlight and carbon dioxide from the air to make their own food

picture of the ozone molecule

stratosphere

UV-B radiation causes

sunburn, genetic damage, and skin cancer in humans

Though it is not completely filtered out

the ozone layer is essential for protecting us from excessive levels of this highly dangerous radiation. Without the ozone layer, sunburns and skin cancer would be much more prevalent and deadly on Earth.

picture of the International Space Station

thermosphere

Venus' atmosphere has too much carbon dioxide

to support any life as we know it; it would kill us

picture of rain clouds with rain coming down

troposphere

Which component of the atmosphere is gaseous water?

water vapor

If you tried to land a space ship on Venus

you would have to get through the thick acidic clouds, then you would have to survive the hurricane force winds that blow around on the planet at speeds of over 800 km/hr. Once you got out of your spaceship, you would have to breathe fiery hot, acidic, poisonous air