Atmosphere vs Space
Atmosphere is a layer of gas around the bodies in space, especially around the planets and stars. The empty region in the universe is referred to as the space. Atmosphere and Space have very contrasting properties due to the fact that one contains matter and the other doesn’t.
Atmosphere
If a massive body has enough gravity, it is often seen that gasses are accumulated around the surface of the body. This layer of gas is often referred to as the atmosphere. It is observed that many of the astronomical bodies orbiting around the stars, such as planets, dwarf planets, natural satellites, and asteroids have layers of gas on top of the surface. Even the stars have atmospheres. The density of this accumulated gas layer depends on the gravitational intensity of the body and the solar activity within the system. Stars have large atmospheres while satellites may have relatively thin atmospheres. Some planets may have dense atmospheres.
The atmosphere of the Sun extends beyond the visible surface of the sun and is known as the corona. Due to high radiation and temperature, almost all the material there is in the plasma state. Terrestrial planets like Venus and Mars have considerably dense atmospheres. The Jovian planets have highly dense and large atmospheres. Some of the satellites in the solar system, such as Io, Callisto, Europa, Ganymede, and Titan have atmospheres. Dwarf planets Pluto and Ceres have very thin atmospheres.
Earth has its own unique and dynamic atmosphere. It acts as a protective layer for the life on the planet. It protects the planet surface from ultraviolet radiation from the sun. Also, the temperature of the planet is kept at a higher level by retaining some of the heat energy received by the planet. The extreme differences in temperature due to the altitude and position relative to the sun are moderated through the convective nature of the atmosphere. Pressure at the mean sea level due to the atmosphere is 1.0132×105Nm-2.
Earth’s atmosphere has following composition;
|
Gas |
Volume |
|---|---|
|
Nitrogen (N2) |
780,840 ppmv (78.084%) |
|
Oxygen (O2) |
209,460 ppmv (20.946%) |
|
Argon (Ar) |
9,340 ppmv (0.9340%) |
|
Carbon dioxide (CO2) |
394.45 ppmv (0.039445%) |
|
Neon (Ne) |
18.18 ppmv (0.001818%) |
|
Helium (He) |
5.24 ppmv (0.000524%) |
|
Methane (CH4) |
1.79 ppmv (0.000179%) |
|
Krypton (Kr) |
1.14 ppmv (0.000114%) |
|
Hydrogen (H2) |
0.55 ppmv (0.000055%) |
|
Nitrous oxide (N2O) |
0.325 ppmv (0.0000325%) |
|
Carbon monoxide (CO) |
0.1 ppmv (0.00001%) |
|
Xenon (Xe) |
0.09 ppmv (9×10−6%) (0.000009%) |
|
Ozone (O3) |
0.0 to 0.07 ppmv (0 to 7×10−6%) |
|
Nitrogen dioxide (NO2) |
0.02 ppmv (2×10−6%) (0.000002%) |
|
Iodine (I2) |
0.01 ppmv (1×10−6%) (0.000001%) |
Earth`s Atmosphere
Structurally, the earth`s atmosphere is divided into several layers based on the physical properties of each region. The principal layers of the atmosphere are the troposphere, stratosphere, mesosphere, thermosphere, and exosphere.
The troposphere is the innermost layer of the atmosphere and extends approximately 9000m above the sea level at the poles and 17000m around the equator. Troposphere is the most dens region of the atmosphere and contains about 80% of the total mass of the atmosphere.
The stratosphere is the layer above the troposphere, and they are separated by a region called the tropopause. It extends from the tropopause up to 51000m from the sea level. It contains the infamous Ozone layer and absorption of the UV radiation by this layer protects the life on the planet surface. The boundary of the stratosphere is known as the stratopause.
Mesosphere lies above the stratosphere and extends up to 80000-85000 m above the sea level from the stratopause. Within the mesosphere, the temperature decreases with the height. The top layer of the mesosphere is considered as the coldest place on earth, and the temperature may be as low as 170K. The upper boundary of the mesosphere is the mesopause.
Thermosphere, which is the layer above mesosphere, extends beyond the mesopause. The actual height of the thermosphere is dependent on the solar activity. The temperature of this region increases with altitude as a result of the low density of gas. The molecules are far apart, and the solar radiation gives kinetic energy to these molecules. The increased motion of the molecules is registered as an increment of the temperature. Upper boundary of the thermosphere is the thermopause. The International Space station is orbiting the earth within the thermosphere.
Region of atmosphere beyond thermopause is known as the exosphere. It is the uppermost layer of the earth’s atmosphere and very thin compared to the lower atmospheric regions. It is mainly composed of Hydrogen and Helium and atomic oxygen. The region beyond the exosphere is the outer space.
Space
The void beyond the earth`s atmosphere can be called as the outer space. More precisely the empty vast regions between stars are known as the space. From earths point of view, there is no boundary where the outer space begins. (Sometimes exosphere itself is considered as a part of outer space)
The space is nearly a perfect vacuum, and the temperature is nearly absolute zero. The average temperature of the space is 2.7K. Therefore, space environment is hostile for the life forms (but some life forms can survive these conditions; ex. tardigrades). Also, the space has no boundary. It extends to the boundary of the visible universe. Therefore, space extends beyond our visible horizon.
Space is also divided into different regions for convenience of study and reference. The region of space around the planet is known as the Geospace. The space between the planets of the solar system is called interplanetary space. Interstellar space is the space between the stars. Space between galaxies is referred to as intergalactic space.
What is the difference between Atmosphere and Space?
• Atmosphere is the layer of gas accreted around a mass with sufficient gravity. Space is the void between stars, or the region beyond the atmosphere.
• Atmosphere consists of gas molecules and the temperature varies depending on the height from the sea level. The density of the atmosphere also decreases with the height. Atmospheres can support life.
• Space is empty and almost a perfect vacuum. Atmosphere is made of a gasses and pressure decrease with the altitude from maximum at the lowest surface level.
• Temperature of the space is near absolute zero, which is 2.7 Kelvin. The temperature of the atmosphere is higher than the outer space and depends on the type of the star, distance from the star, gravity, the size of the body (planet), and the stellar activity.