You don't want carbon dioxide (CO2) build up in your space suit. Even those who argue to love huge CO2 emissions into our atmosphere should learn from the AP news: Two astronauts cut short their spacewalk and hurried back to the safety of the international space station (ISS) on Wednesday after a suit problem resulted in rising carbon dioxide levels for one of the men.

First, here is an image of a spacewalk. Two astronauts, Robert L. Curbeam (USA) and Christer Fuglesang (Sweden), work to attach a new truss segment to the ISS and begin to upgrade the power grid. This occurred on December 12, 2006.

Spacewalk in 2006
Second, here is a suit, also called Extravehicular Mobility Unit (EMU). You probably know that EMU is worn in an Extravehicular Activity (EVA).

Extravehicular Mobility Unit
Third, NASA claimed Endeavour spacewalker Christopher Cassidy was never in any danger and experienced no symptoms of carbon dioxide buildup. You see pure oxygen is what he should be breathing inside his EMU. "Cassidy's CO2 level stayed well within allowable limits for the shuttle and station atmospheres." The observed upward trend was the reason NASA "did not want to take any chances."

Speaking of loves, here is my favorite astronaut picture of all times. A few meters away from the shuttle Challenger was the astronaut without any EMU tether. He took big chances in the Manned Maneuvering Unit (MMU).

Astronaut Bruce McCandless II, MMU mission specialist on February 11, 1984
Finally, I found one thing extraordinary to say the least. The other EVA astronaut, David Wolf, said "his idea for stringing safety tethers together, with minimal hookups in case of an emergency, worked like a charm. Never thought we'd use it."

Was Wolf's idea included in the EVA procedures? I thought I would never ask.