The atmosphere has changed over millions of years from one lacking oxygen to one that is oxygen-rich, due to the presence of life.

This Web assignment focuses on Titan, the large moon of Saturn. The article to read is called Titan: A Primordial Earth In Our Solar System, and is from the Asia Pacific Space Center, at the site http://www.spacedaily.com/news/early-sol-00e.html. Why might the exploration of Titan give us clues as to the origin of life on Earth? What is the nature of the Titan atmosphere? How does it compare to that of the primordial Earth, and how do we know these things? Along with your answers, please include some nifty pictures of Titan that you find on the Internet.

Ozone is an important constituent of the stratosphere, where it shields us from most harmful amounts of UV radiation.

Please do a visual report - look up and print out comparative pictures that demonstrate ozone depletion. Interpret the data on the graph for the casual reader - that is, what do the colors you see tell you about ozone levels? Make sure your data covers winter and summer for at least the past 10 years. If possible, get graphical data for many more years. Hint: Using the "Images" search function on http://www.google.com is helpful.

Greenhouse gases are those which transmit visible radiation while absorbing UV radiation. This results in heat building up in the atmosphere like in a gardener's greenhouse.

There is considerable debate as to whether the Earth is undergoing a period of Greenhouse Gas-related heating. Your goal is to write a paper that argues both sides of the issue. An excellent starting site is http://www.pbs.org/wgbh/nova/ice/greenhouse.html. Your paper should be predominantly data-driven. This means that you are to look up a good selection of data charts and/or tables to support your arguments.

Smog (historically, the combination of smoke and fog) comes in reducing and photochemical smog. Automobile emissions, in concert with warm temperatures, are responsible for the modern, photochemical, variety.

Let's play "Smog City"!! Please go to the site at http://www.smogcity.com/welcome.htm. Run the simulation. Then write a short paper about what factors most affect the ozone level. Also discuss what factor or factors may have surprised you by their effect (or lack thereof) on the smog level in this city.

Particulate matter is composed of tiny solid or liquid particles that result from a number of natural and industrial processes.

Here's a quickie. Please go the EPA site at http://www.epa.gov/ARD-R5/naaqs/pm_nmap.htm. You will find a map of a group of states with which areas exceeding the federal particulate matter standard are highlighted. Please explain why these particular (as opposed to particulate!) areas exceed the federal standard.

There is general agreement that human technological activities have adversely affected the quality of the atmosphere.

In this section of the textbook, we referred to the conclusions reached by the EPA regarding air quality. Please visit the EPA site at http://www.epa.gov/oar/aqtrnd99/. There is a good deal of data there. Pick and choose the data you think are necessary to make the case that the air quality in the U.S. is getting better or worse. Next, do the same for a site outside the U.S. by visiting the following site http://www.aeat.co.uk/netcen/airqual/networks/aqworldlinks.html.