Section 1 - Composition of the Atmosphere

1. Section 1 - Composition of the Atmosphere • Atmosphere is a mixture of gases that surrounds a planet, such as Earth. • The most abundant elements in air are the gases nitrogen (78%), oxygen (21%), and argon (0.9%). Chapter 22

2. Composition of the Atmosphere • In addition to containing gaseous elements and compounds Carbon Dioxide (CO²) and Water Vapor (H²O). • The atmosphere also carries various kinds of tiny solid particles, such as dust and pollen. Chapter 22

3. History of the Atmosphere #1 • The first atmosphere would have consisted of gases in the solar nebula, primarily hydrogen and helium. • As the solar nebula dissipated, these lighter gases would have escaped, partly driven off by the solar wind Chapter 22

4. History of the Atmosphere #2 • The next atmosphere, consisting largely of nitrogen plus carbon dioxide and inert gases, was produced by outgassing from volcanism. Chapter 22

5. History of the Atmosphere#2 • Gases like water vapor (H²O), nitrogen (N), ammonia (NH³), methane (CH4), argon (Ar), sulfur dioxide (SO²) and carbon dioxide (CO²) would contribute to the atmosphere we have today. Chapter 22

6. History of the Atmosphere #2 • Water-related sediments have been found dating from as early as 3.8 billion years ago. • Debate goes on today as to where our water comes from: Chapter 22

7. History of the Atmosphere #2 • (A) Planet cools, the temperatures drop, allowing water vapor to condense and fall as rain. or • (B) Water was delivered during The Late Heavy Bombardment Period by (Comet, Asteroid) Chapter 22

8. Stromatolites oldest fosil 2.7 b.y.a. History of the Atmosphere #3 • Before photosynthesis evolved, Earth's atmosphere had no free oxygen (O2). • Our oxygen would come from early Cynobacteria (blue-green algae -stromatolites), splitting molecules of CO² through photosynthesis and emitting (O²) as a waste product. Chapter 22

9. History of the Atmosphere #3 • Perhaps as early as 3.5 billion years ago- The oxygen they produced would have almost instantly been removed from the atmosphere by weathering of reduced minerals, most notably iron. • Free oxygen would begin to build up 2.4 billion years ago creating our third atmosphere. Chapter 22

10. History of the Atmosphere • Oxygen concentration have fluctuated between 15% and a maximum of 35% of atmospheric volume and hit a peak 300 million years ago which most likely contributed to the large size of insects and amphibians at that time. Chapter 22

11. Oxygen in the Atmosphere • Today oxygen makes up about 21% of Earth’s atmosphere. • Land and ocean plants produce large quantities of oxygen in a process called photosynthesis to maintain this level. Chapter 22

12. Nitrogen in the Atmosphere • The history of Nitrogen is less complex because its evidence is found in volcanoes. • Sunlight and its ability in the upper atmosphere to break down ammonia (NH3) released by volcanoes, would release nitrogen into the atmosphere over billions of years. Chapter 22

13. Nitrogen in the Atmosphere • Nitrogen makes up about 78% of Earth’s atmosphere and is maintained through the nitrogen cycle. • Nitrogen is removed from the air mainly by the action of nitrogen-fixing bacteria. • Decay releases nitrogen back into the atmosphere. Chapter 22

14. Argon in the Atmosphere • Argon's most common isotope, Ar-40, became a part of the Earth's atmosphere after K-40, a radioactive isotope of potassium, decayed from the Earth's crust. • NASA probes have discovered argon in Mars & Mercury's atmosphere and on Saturn's moon Titan. Chapter 22

15. Atmospheric Pressure • Atmospheric pressure is the force per unit area that is exerted on a surface by the weight of the atmosphere. • Gravity holds the gases of the atmosphere near Earth’s surface and as a result, the air molecules are compressed together and exert force on Earth’s surface. Chapter 22

16. Atmospheric Pressure • Atmospheric pressure is exerted equally in all directions—up, down, and sideways. • Earth’s gravity keeps 99% of the total mass of the atmosphere within 20 miles of Earth’s surface. Chapter 22

17. Atmospheric Pressure • Because the pull of gravity is not as strong at higher altitudes, the air molecules are farther apart and exert less pressure on each other at higher altitudes. Chapter 22

18. Atmospheric Pressure • At sea level, the air pressure is about 14.7 pounds per square inch. • As your altitude increases (for example, if you climb a mountain), the air pressure decreases. • At an altitude of 10,000 feet, the air pressure is 10 pound per square inch (and there is less oxygen to breathe). Chapter 22

19. Lesson 2 - Layers of the AtmosphereBaumgartnerjump • In general, air pressure and density decrease in the atmosphere as height increases. • However, temperature has a more complicated profile with altitude.

20. Layers of the Atmosphere • Earth's atmosphere has a distinctive pattern of temperature changes with increasing altitude and allow scientist to indentify five main layers.

21. Layers of the Atmosphere • The five main layers of the atmosphere from top to bottom are the • 5th Layer - Exosphere. • 4th Layer - Thermosphere • 3rd Layer- Mesosphere • 2nd Layer- Stratosphere • 1st layer - Troposphere

22. 1)The Troposphere • The Troposphere is the layer closest to Earth’s surface. • From the extreme desert temperature’s of over a 120° F, the temperature drops at a constant rate as altitude increases to a low of (-)76° F.

23. 1)The Troposphere • The most important fact to the troposphere is that almost all of the water vapor for weather and carbon dioxide in the atmosphere is found in this layer.

24. The Troposphere • From the ground up to the top of this layer is about 10 miles in height and from there the temperature stops decreasing. • This part of the layer is called the tropopauseand represents the upper boundary of the troposphere. Chapter 22

25. 2) The Stratosphere • The second layer of the atmosphere is the stratosphere. • The temperature at the bottom of the stratosphere starts at about -76°F and increases as attitude increases to a high of 32°F. Chapter 22

26. Stratosphere • The second layer of the atmosphere starts at about 10 miles high and goes up to an altitude of 30 miles, which means it is twice the size of the troposphere.

27. Stratosphere • Commercial airliners typically cruise in the lower reaches of the stratosphere at altitudes of 30,000–39,000 ft. • This optimizes fuel burn, drag on the airframe and allows them to stay above extreme turbulence and weather.

28. Ozone Layer • The stratosphere is the most important layer in our atmosphere because it contains a thick 10 mile layer of ozone, which absorbs harmful ultraviolet radiation from the sun. • It is made up of three oxygen atoms - O³, unlike the air we breathe which is O².

29. Ozone Layer • This process started about a 1.0 billion years ago when ozone gas began to form in the stratosphere through the process known as the ozone-oxygen cycle. • The cycle occurs when short-wavelength UV light from the sun hits a molecule of oxygen gas.

30. Ozone Layer • Light has so much energy that it breaks the oxygen bond holding the atoms together, thus creating two oxygen atoms (O² = O + O). • From there the single atoms of oxygen (O) combined with remaining oxygen (O²) to form ozone (O³) molecules.

31. Ozone Layer Damage • The ozone layer is located at the bottom of the stratosphere and then extends upward for about 10 miles. Chapter 22

32. Ozone Layer Damage • The ozone layer is very effective at absorbing UV rays, in fact it is considered a “greenhouse gas”. • The ozone layer is a mixture of our major atmospheric gases (N² and O²) along with the O³ molecules. Chapter 22

33. Ozone Layer Damage • Invented in the 1920s, CFCs found in hair sprays and aerosol cans proved to be an exceptional problem for ozone, because many of these synthetic chemicals can persist for decades, allowing them to make their way into the upper atmosphere.

34. Ozone Layer Damage • In that rarefied air, ultraviolet light breaks the molecular bonds in CFCs and free chlorine atoms get released. • Chlorine then destroys ozone molecules by "stealing" their oxygen atoms.

35. Ozone Layer Damage • Scientists had theorized since the 1970’s about the chemistry that could lead to ozone depletion. • In May 1985 scientists with the British Antarctic Survey shocked the world when they announced the discovery of a huge hole in the ozone layer over Antarctica. Chapter 22

36. Ozone Layer Damage • In 1987, delegates from around the world signed the Montreal Protocol designed to protect the ozone layer by phasing out the production of a number of substances believed to be responsible for ozone depletion. Chapter 22

37. Ozone Layer Damage • Today the ozone hole, which was first spotted 25 years ago, appears headed for a happy ending, thanks to international action. • Some scientists project that by 2080 global ozone will return to 1950’s levels. Chapter 22

38. Lesson 3 – The Mesosphere #3Nasa Space Station Aurora’s • The Mesosphere is the third layer to our atmosphere or middle layer. • It starts at about 30 miles and goes up to about 50 miles high.

39. The Mesosphere • As you get higher up in the mesosphere, the temperature gets colder. • Temperature ranges from 32°F at the bottom to about a -150°F at the top making this the coldest place on Earth. Chapter 22

40. The Mesosphere • Scientists know less about the mesosphere than about other layers of the atmosphere because it is hard to study. • Weather balloons and jet planes cannot fly high enough to reach the mesosphere and the orbits of satellites are above the mesosphere. Chapter 22

41. The Mesosphere • What we do know is that millions of meteors enter the atmosphere, an average of 40 tons per day. • Within the mesosphere most melt or vaporize as a result of collisions with the air particles contained there. Chapter 22

42. 4) The Thermosphere • The thermosphere is the 4th layer of the atmosphere and in this layer temperatures increases as the altitude increases. • It is the largest layer of the atmosphere as is spans from 50 miles above ground to 400 miles. Chapter 22

43. Ionosphere • The lower region of the thermosphere, at an altitude of 50 miles to 250 miles, is commonly called the ionosphere. • The ionosphere is the region where Earth’s atmosphere blends into the almost complete vacuum of space. Chapter 22

44. Ionosphere • The ionosphere is distinguished because it is ionized by solar radiation and forms the inner edge of the magnetosphere.

45. Thermosphere • It is the ionosphere and the interactions between solar radiation that causes the phenomena known as auroras. • The temperatures leave the -130°F and go up to 400°F.

46. Reason for Aurora’s • The aurora’s are cause when the massive amounts of electrons emitted from the Sun are carried by the solar winds. • They are then attracted in by our magnetism at the poles where they then crash into our atmosphere.

47. Reason for Aurora’s • When the electrons collide with the oxygen and nitrogen atoms, the atoms are ionized, and this ionization causes the atoms to become excited and emit photons of light. • This reaction can be seen elsewhere including Jupiter. Chapter 22

48. 4th Layer - The Thermosphere • Although part of Earth's atmosphere, the air density is so low in this layer that most of the thermosphere is what we normally think of as outer space which is 62 miles above. Chapter 22

49. The Thermosphere • Much of the X-ray and UV radiation from the Sun is absorbed in the thermosphere which is why most satellites and the space station orbit within the thermosphere. Chapter 22

50. Orbit Height ISS • The ISS is maintained at an orbital altitude of between 205 miles and 255 miles and travels in orbit around Earth at a speed of roughly 17,150 miles per hour (~5 miles per second) completing 15.7 orbits per day.  Chapter 22