This Topic in Depth begins with a Web site maintained by Dr. Richard B. Gomez of George Mason University called Space Debris (1). The site is offered as a slide presentation, which explains what space debris is, where it comes from, if it's dangerous, what is known about it, and what can be done about it. The very interesting site is perfect for non-experts because of its simple descriptions and abundance of graphics. The second site from Space.com is an article written by Robert Roy Britt entitled Space Junk: The Stuff Left Behind (2). Visitors can read about the number of objects being tracked (at the time the article was written), what the total weight of these objects is, view a table of the number of various pieces of space junk by country, and even find out it if there is a risk of getting hit in the head by these objects. The next site, Nature's Tiniest Space Junk (3), is offered by NASA's news portal Science@NASA Web site. The page describes how scientists are monitoring tiny dust sized meteoroids that are constantly flying around our planet that have the potential to be quite dangerous. For those really interested, the site lets people listen to audio files of the meteor radar in action. The fourth site on space junk, maintained by the Texas Advanced Computing Center, is a Simulation of Orbital Debris Shielding Performance at High Impact Velocities (4). The page highlights the work of Dr. Eric Fahrenthold, who is simulating orbital debris shielding performance at high impact velocities. A basic description of the work is offered along with the simulation itself, which shows a piece of space debris striking a surface. Next, from NASA's Hazards Assessment Web site, comes the Hypervelocity Impact Test Facility: Orbital Debris and Micrometeoroids (5) page. Readers can find out more on the problem of space junk, why NASA feels its so important to study simulating particle impacts on spacecraft, the lightweight shields that are in place on the International Space Station, and more. The sixth site is an article that appeared in the Bulletin of the Atomic Scientists by Joel Primack called Pelted by Paint, Downed by Debris (6). Although there's not a large amount of content on the site, it does give some interesting information on a different aspect of the subject. The author describes how any missile defense program could be detrimentally affected by space debris and suggests the need for space agencies to take active steps to prevent its buildup. The National Academies Press offers the next site, which is actually an online book on Protecting the Space Station from Meteoroids and Orbital Debris (7). Contents include risk management strategies for the space station, debris modeling, shielding the station, collision warning and avoidance, and more. The last site is from the Aerospace Corporation and its Center for Orbital and Reentry Debris Studies (8). Visitors will find an introduction to the Center, the basics of space debris, what happens during satellite reentry, re-entry data and predictions, additional links, and more.