Earth’s Atmosphere
Atmosphere
by Jerry Coffey
An atmosphere is a layer of gases that may
surround a celestial body that is held in place by
the gravity of that body. An atmosphere may be
retained for billions of years if gravity is high
and the atmosphere‘s temperature is low. Some
planets(gas giants) consist mainly of various
gases, but only their outer layer is their
atmosphere.
A stellar atmosphere is the outer region of a star.
This includes the portion from the photosphere
outwards. Low-temperature stars may form
compound molecules in their outer atmosphere.
Earth‘s atmosphere provides the molecules
needed for life and protects organisms from
damage by ultraviolet radiation. Its current
composition is the product of billions of years of
biochemical modification by those living
organisms.
Atmospheric makeup is generally related to the
chemistry and temperature of the closest solar
nebula during planetary formation and the
subsequent escape of interior gases. Original
atmospheres underwent a great deal of evolution
over time and the varying properties of each
planet resulted in very different atmospheres
and conditions. The atmospheres of Venus and
Mars are composed of carbon dioxide, nitrogen,
argon, oxygen, and trace gases, while the
atmosphere on Earth is largely governed by the
by-products of the very life that it sustains. It
contains 78% nitrogen, 21% oxygen, and trace
amounts of water vapor, argon, carbon dioxide,
hydrogen, helium, and other gases. The low
temperatures and higher gravity of the gas
giants(Jupiter, Saturn, Uranus, and Neptune)
allows them to readily retain gases with low
molecular masses, so these planets have mainly
hydrogen-helium atmospheres.
Two satellites in the outer planets possess
atmospheres. Titan(one of Saturn’s moos) and
Triton(one of Neptune’s moons) have
atmospheres mostly comprised of nitrogen.
Pluto‘s atmosphere is made of nitrogen and
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methane. It is in gas form when at perihelion
and frozen at aphelion.
The Hubble Space Telescope was used to
determine the composition of an extra-solar
planet. The planet, HD 209458b, is a gas giant
in the Pegasus constellation. Hydrogen,
oxygen, sulfur, and carbon are steadily
escaping the atmosphere that is thought to be
at 1,000K.
The atmosphere has different meanings for
different fields of study. A geologist looks to
it for the morphology of a planet. A
meteorologist looks for climate changes and
storm prediction, while a biologist looks to it
for early signs of life and clues to evolutionary
steps.
Composition of the Earth’s
Atmosphere
by Fraser Cain
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Earth’s Atmosphere
Breathe in and you can appreciate that the
Earth‘s atmosphere has everything needed to
support life on Earth. But what’s in it? Let’s
take a look at the composition of the Earth’s
atmosphere. Of course, things haven’t always
been balanced they way they are today. But
more of that in a second.
The Earth’s atmosphere is composed of the
following molecules: nitrogen (78%), oxygen
(21%), argon (1%), and then trace amounts of
carbon dioxide, neon, helium, methane, krypton,
hydrogen, nitrous oxide, xenon, ozone, iodine,
carbon monoxide, and ammonia. Lower
altitudes also have quantities of water vapor.
The atmosphere we have today is very different
from the Earth’s early atmosphere. When the
planet first cooled down 4.4 billion years ago,
volcanos spewed out steam, carbon dioxide and
ammonia, and it was 100 times as dense as
today’s atmosphere.
The earliest bacteria, known as cyanobacteria,
were probably the first oxygen-producing
organisms on Earth. Approximately 2.7 to 2.2
billion years ago, they released large amounts of
oxygen and sequestered the carbon dioxide. As
oxygen was released, it reacted with ammonia to
release nitrogen. The carbon dioxide in the
atmosphere is exhaled by plants (and produced
by human industry burning fossil fuels).
Gases In The Atmosphere
they’ve exceeded their ideal levels. Anything
that comes in excess is not good, right?
At ideal levels, greenhouse gases play an
important role in keeping our planet warm
enough for us and other organisms to live
comfortably. Unfortunately, the rapid rate of
industrialization has caused greenhouse gases
to accumulate, forming a layer too thick for
infrared radiation (which originally came in
from the Sun as solar radiation) to escape.
The different gases in the atmosphere actually
make up five principal layers. Starting from
the lowest layer, there’s the Troposphere,
followed by Stratosphere, then the
Mesosphere, then Thermosphere, and finally
the Exosphere.
The peak of Mount Everest, high as it is, is
still part of the Troposphere. The Stratosphere
is the layer at which most weather balloons
fly. The Mesosphere is where meteors mostly
ignite. The Thermosphere is where the
International Space Station orbits.
Since the Karman line (which serves as the
boundary between the Earth‘s immediate
atmosphere and outer space) is found in the
lower region of the Thermosphere, much of
this layer of gases in the atmosphere is
considered outer space. Finally, the exosphere,
being the outermost layer, is where you can
find the lightest gases: hydrogen and helium.
by John Carl Villanueva
There are different gases in the atmosphere.
There’s nitrogen (the most abundant of them
all), oxygen, and argon. There are of
course a lot more but they’re no more
than 1% of the entire atmosphere.
Many properties of the gases in the
atmosphere are dependent on the altitude at
which they are found. For instance, average
Among the minority are the
greenhouse gases, carbon dioxide
being the most prominent of them all.
These gases are presently cast as
harmful to the planet, being the
primary cause of global warming. Of
course, they’re only harmful because
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Earth’s Atmosphere
density of these gases generally decrease as one
rises to higher altitudes. As a result, the pressure
(being due to the collisions of the particles that
make up the gas) also decreases in the same
manner.
Since the force of gravity pulls down on the
masses of these gases, the heavier gases are
typically found near the surface of the Earth
while the lightest ones (e.g. hydrogen and
helium) are found in higher altitudes. All these
properties are just generalizations though.
Temperature and fluid dynamics also influence
these properties.
What Color is the Sky
This process is called diffused sky radiation.
So to review, we color because objects due to
texture of dyes and surfaces absorb all light
wavelengths and reflect back one or more.
The reason we see the sky as blue is because
the molecules in the air scatter the light
absorbing most wavelengths of light except
for blue.
In addition to this the sky is gray and overcast
because of the water droplets in the
atmosphere in the forms of clouds and
humidity. water refracts light equally unlike
air molecules in the atmosphere. This means
we get the entirety of white light only it is
dimmer just like when you shine a light
through a white sheet.
by Tega Jessa
If you are a parent or are old enough to babysit
younger relatives there is one question children
ask that stumps most adults. It’s what color is
the sky or why is the sky blue. This article will
tell you why and do it in as simple a way as
possible so that the next time a kids ask the
question you have a good answer.
To understand why the sky is blue you need to
remember how color works. Color is largely
caused by how well an object absorbs the light
spectrum. When you see a blue sky you only see
blue because all the other colors were absorbed
in the air. Any object with color works that way.
For example a red ball is read because all the
colors of light are absorbed by the ball except
for red. This reflected light is what gives the
object color.
This is what happens with the sky. The
atmosphere is denser than we imagine and the
different gases give the atmosphere unique
properties in how it absorbs, diffuses, and
reflects light. When sunlight passes through our
atmosphere a portion of it is scattered and
absorbed. The remainder either reaches the
surface or is reflected back. The portion that
makes it to us observers is 75 percent.
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The fact we see a blue sky is good thing
because its shows that are atmosphere is at
work shielding us from the full energy of the
sun‘s rays. While the sun is the largest source
of energy to our planet, a lot of its high energy
radiation that is deadly for living things. Our
atmosphere plays it part by shielding us from
that. So when you see a blue sky with your kid
you can tell them it means the sky is acting
like a huge shade blocking out the bad parts of
the sun.
Earth’s Atmosphere is Leaking into
Space
by Nancy Atkinson
Oxygen is constantly leaking out of Earth’s
atmosphere and into space. Measurements
taken by satellites during the 1980s and 1990s
showed the escaping ions were traveling faster
the higher they were observed. This implied
that some sort of acceleration mechanism was
involved. Now, new work on data collected by
a group of formation-flying satellites called
Cluster shows that Earth’s own magnetic field
is accelerating the oxygen away. But don’t
worry, compared to the Earth’s stock of the
life-supporting gas, the amount escaping is
negligible. However, in the far future when
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Earth’s Atmosphere
the Sun begins to heat up in old age, the balance
might change and the oxygen escape may
become significant.
From data collected from 2001 to 2003, Cluster
amassed information about beams of electrically
charged oxygen atoms, known as ions, flowing
outwards from the polar regions into space.
Cluster also measured the strength and direction
of the Earth’s magnetic field whenever the
beams were
present.
“We are beginning to realize just how many
interactions can take place between the solar
wind and the atmosphere,” says Nilsson.
Energetic particles from the solar wind can be
channeled along the magnetic field lines and,
when these impact the atmosphere of the
Earth, they can produce aurorae. This occurs
over the poles of Earth. The same interactions
provide the oxygen ions with enough energy
to accelerate out of the atmosphere and reach
the Earth,s
magnetic
environment.
Hans Nilsson,
Swedish
The Cluster data
Institute of
were captured over
Space Physics,
the poles with the
headed a team
satellites flying at
of space
an altitude of
scientists who
anywhere between
analyzed the
30,000 and 64,000
data. They
kilometers. The
discovered that
data is helping
the oxygen ions
scientists to
were being
understand what
accelerated by
might happen in the
changes in the
future. “We can
direction of the magnetic Artist impression of ions leaking into space. Credit:
only predict these future
NASA/ESA
field. “It is a bit like a
changes if we
sling-shot effect,” says Nilsson.
understand the mechanisms involved” says
Nilsson.
“Having all four Cluster spacecraft was essential
to the analysis because it gave astronomers a
Source: European Space Agency
way to measure the strength and direction of the
magnetic field over a wide area. Cluster allowed
us to measure the gradient of the magnetic field
The Early Earth’s Atmosphere was
and see how it was changing direction with
Similar to Titan
time,” says Nilsson.
by Fraser Cain
Before the space age, scientists believed that
Earth’s magnetic field was filled only with
particles from the solar wind, the constant sleet
of particles that escapes from the Sun. They
thought this formed a large cushion that
protected the Earth’s atmosphere from direct
interaction with the solar wind.
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The thick organic haze that shrouds Titan is
similar to what we had here on Earth billions
of years ago; an environment that might have
helped early life get a foothold. NASA
researchers set up several experiments that
reproduced the atmosphere in the early Earth
and Titan today. The Earth experiments
produced tremendous amounts of organic
4
Earth’s Atmosphere
material, which could have been one of the
ways life first appeared.
Organic haze in the atmosphere of Saturn‘s
moon, Titan, is similar to haze in early Earth’s
air — haze that may have helped nourish life on
our planet– according to a NASA Astrobiology
Institute study released Nov. 6, 2006.
Study scientists simulated both the atmospheric
conditions of early Earth and those of presentday Titan. Their study, “Organic Haze on Titan
and the Early Earth,” describing the scientists’
work, appears in Proceedings of the National
Academy of Sciences. The principal author is
Melissa Trainer, a NASA Astrobiology Institute
postdoctoral fellow at the University of
Colorado, Boulder.
“It’s exciting to see that the early Earth
experiments produced so much organic matter,”
said Carl Pilcher, director of the NASA
Astrobiology Institute, at NASA Ames Research
Center, Moffett Field, Calif. “An organic haze
produced this way on early Earth could have
contributed to the formation and sustenance of
life.”
According to the study’s researchers, their
experiments help scientists interpret
observations of Titan’s atmosphere from
NASA’s Cassini mission, while also showing
how a major source of organics could have been
produced on Earth billions of years ago.
The researchers reported that the aerosols
produced in the laboratory could serve as
analogs for the observed haze in Titan’s
atmosphere. The scientists also estimated that
aerosol production on early Earth could have
served as a primary source of organic material
to the surface.
“This paper shows one of the ways in which the
study of other worlds can help us understand
Earth,” said Chris McKay, a scientist at NASA
Ames and one of the study’s co-authors. “Titan
has a thick organic haze layer, and this work
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started out to understand the chemistry of that
alien organic haze. Then we realized that we
could apply the same approach to the organic
haze on early Earth.”
“We hope to determine how the organics were
made and their chemical nature,” McKay
observed. The scientists reported that when
sunlight hits an atmosphere of methane and
nitrogen, like the atmosphere of Titan today,
aerosol particles form. When an atmosphere
also contains carbon dioxide, as in the
atmosphere of ancient Earth, different kinds of
aerosols form.
The scientists used a special ultraviolet-light
lamp to produce particles in the simulated
atmospheres, and measured the chemical
composition, size and shape of the resulting
particles.
“It’s somewhat similar to the smog in Los
Angeles,” Trainer explained. “Today’s haze
on Earth is also created photochemically,
which means sunlight powers chemical
reactions in the atmosphere. However, the
early atmosphere of Earth had different gases
present, so chemical composition of the early
haze is very different than the haze we have
today. There also would have been a lot more
of it.”
Original Source: NASA News Release
Where is the Ozone Layer Located
by Tega Jessa
The Ozone Layer is the portion of the
atmosphere that contains high levels of the
oxygen molecule ozone. This molecule plays
an important role acting as a natural UV shield
for the Earth. You may wonder where is the
ozone layer located to play such a vital role so
effectively. The Ozone layer is actually
located in the stratosphere in a region that is
10 to 50 km above the Earth.
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Earth’s Atmosphere
So why is the Ozone layer so important? As
mention before the secret lies in oxygen
molecules. Normal oxygen in its natural
molecular state is made up of only two atoms.
However this changes when oxygen in the
thermosphere is exposed the Sun‘s ultraviolet
rays. The rays separate oxygen molecules the
free oxygen joins with the remaining two atom
oxygen molecules to create ozone. This process
might seem simple but it helps to screen out
99.5 percent of the ultraviolet radiation that the
Sun sends towards earth. The times that the
ozone layer didn’t screen out this type of
radiation at such levels life was almost wiped
out according to the geologic record.
You might think that this is an exaggeration
until you observe the biological damage UV
rays can do. We have already seen the harm
caused when people don’t take the proper
precautions when going to the beach. The least
harm comes in the form of sun burn. People
overexposed to the UV rays that do make it to
earth have their skin damaged by the UV energy
that penetrates their skin. However it gets more
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serious the longer a person is exposed to UV
rays. The reason is because the damage gets to
the cellular level causing cancers and genetic
damage. Essentially it’s like being exposed to
a nuclear reactor in melt down. The high
energy radiation over time would accumulate
harm in living tissue until it killed the
organism exposed to it.
Despite its importance industry produced and
released chemicals into the air that interfered
with the ozone cycle. The main problem
chemical CFC’s prevented oxygen molecules
from complete the bonding process that is
important for the completion of the ozone
cycle this caused a major depletion of ozone
in key areas of the Earth’s atmosphere. This is
huge when the natural concentration of ozone
was already quite low. This just goes to show
the delicate balance that was upset.
Fortunately nations upon hearing the harm
caused started bans on CFC’s while industry
tried to find alternatives to use in products.
The result started to show with ozone
depletion actually slowing down and
reversing with scientist predicting
recovery within the next century.
6