Earth’s Atmosphere: all the layers

September 10, 2022

Written by: Caroline Kim

A part of our environment that often goes unnoticed is the function of earth’s atmosphere. Though we quite see everyday the way we see trees, it plays a significant role in sustaining life on earth: providing protection from solar radiation, balancing gasses, and regulating climate (Kazmeyer). The sequence from inner to outer of the layers of our atmosphere are as follows: troposphere, stratosphere, mesosphere, thermosphere, ionosphere, and exosphere.

The troposphere, reaching about 33,000 feet above sea level, holds nearly 80% of the atmosphere’s mass due to its containing the most moisture out of all the layers (Center for Science Education). This innermost layer of the earth’s atmosphere contains most weather such as rain, clouds, snow, etc. The air temperature in this layer tends to be warmer in the lower regions, and colder higher up. This would account for snow laying on the peak of mountains, or why it’s colder when you ski at the top than at the base (Center for Science Education).

The stratosphere, the second layer, spans roughly 6-31 miles above ground. Unlike the troposphere, temperatures rise with altitude and also contain very little water vapor (Center for Science Education). This is the layer that contains the famous ozone layer, which is responsible for absorbing “almost all of the sun's harmful ultraviolet light” (Rutledge). This is important, because without protection, the radiation can “penetrate organisms’ protective layers, like skin, damaging DNA molecules in plants and animals” (Rutledge). The concern here is that chlorofluorocarbon molecules are diminishing this protective ozone layer, which can be detrimental for life on earth (Rutledge). In the U.S., most of this ozone depletion can be blamed on severe storm systems and high levels of atmospheric carbon dioxide/methane (BioExplorer.net).

The mesosphere, spanning 31-53 miles above, is where the coldest temperatures can be found (-130 degrees Fahrenheit at the top of this layer)(Center for Science Education). In this layer exists the unique “noctilucent clouds” or “polar mesospheric clouds”, which can be characterized by their high altitude and dryness (Center for Science Education). Though this layer remains fairly unexplored, it is known for being the layer in which meteors vaporize; in other words, this is where meteors burn up (Mesosphere).

The thermosphere stretches from approximately 56-311/621 miles high (Center for Science Education). Air density is extremely low in this layer, and it can be considered as outer space; “The space shuttle and the International Space Station both orbit Earth within the thermosphere” (Center for Science Education). In this layer, molecules rarely collide, and are broken apart due to UV and X-ray photons from the sun (Center for Science Education).

The ionosphere, unlike the previous layers, is not confined to a specific boundary. Essentially, it is the collective group of “electrically charged atoms and molecules” within the earth's molecules (Center for Science Education). Due to high incoming energy, molecules are constantly broken and formed. The free electron characterization of this layer allows for the ionosphere to “ absorb or dampen radio signals, or they can bend radio waves, as well as reflecting the signals as described above” (Center for Science Education). The ionosphere, susceptible to change, can be influenced by weather and space weather: “hurricanes or large thunderstorm systems, can create pressure waves that ripple up into the ionosphere” and “changing magnetic and electric conditions in space… along with other events like bursts of charged particles — are called space weather and usually connected to solar activity” (10 Things to Know about the Ionosphere – NASA Solar System Exploration). This unique layer even glows (airglow- atoms/molecules emit light to release incoming energy from the sun) (10 Things to Know about the Ionosphere – NASA Solar System Exploration).

The final layer, the exosphere, begins at about 300 miles high and 6200 miles thick (Exosphere). The low molecular densities result in very small collisions, explaining the numerous helium and hydrogen particles (Britannica, The Editors of Encyclopaedia).

All these layer combined allow life on earth to exist, controlling solar energy, particle activity, relates to weather (on earth and space), and impacts systems such as GPS. Though not as tangible, it is still crucial to earth’s function.

Sources:

“Center for Science Education.” The Troposphere | Center for Science Education, https://scied.ucar.edu/learning-zone/atmosphere/troposphere.

“Center for Science Education.” The Stratosphere | Center for Science Education, https://scied.ucar.edu/learning-zone/atmosphere/stratosphere.

Rutledge, Kim, et al. “Ozone Layer.” Edited by Jeannie Evers and Kara West, National Geographic Society, 20 May 2022, https://education.nationalgeographic.org/resource/ozone-layer.

BioExplorer.net. "Top 15 Current Environmental Issues in the US" Bio Explorer, 10 September 2022, https://www.bioexplorer.net/current-environmental-issues-usa.html/.

“Center for Science Education.” The Mesosphere | Center for Science Education, https://scied.ucar.edu/learning-zone/atmosphere/mesosphere.

“Mesosphere.” NASA, NASA, 28 June 2019, https://spaceplace.nasa.gov/mesosphere/en/.

“Center for Science Education.” The Thermosphere | Center for Science Education, https://scied.ucar.edu/learning-zone/atmosphere/thermosphere#:~:text=The%20thermosphere%20is%20a%20layer,621%20miles)%20above%20our%20planet.

“Center for Science Education.” The Ionosphere | Center for Science Education, https://scied.ucar.edu/learning-zone/atmosphere/ionosphere.

“10 Things to Know about the Ionosphere – NASA Solar System Exploration.” NASA, NASA, 10 Dec. 2019, https://solarsystem.nasa.gov/news/1127/10-things-to-know-about-the-ionosphere/.

“Exosphere.” NASA, NASA, 28 June 2019, https://spaceplace.nasa.gov/exosphere/en/#:~:text=The%20exosphere%20has%20gases%20like,breathe%2C%20and%20it's%20very%20cold.

Britannica, The Editors of Encyclopaedia. "exosphere". Encyclopedia Britannica, 9 Aug. 2019, https://www.britannica.com/science/exosphere. Accessed 10 September 2022.

Kazmeyer, Milton. “Importance of the Earth's Atmosphere.” Sciencing, 2 Mar. 2019, https://sciencing.com/importance-earths-atmosphere-5070.html.