An ammonia tank discarded from the International Space Station is expected to reenter the Earth’s atmosphere sometime today. The refrigerator-sized tank was jettisoned during a spacewalk on July 21, 2007 by Astronaut Clayton Anderson, from the end of the station’s robot arm.
NASA usually tries to avoid adding to the debris orbiting the planet, but officials felt they had no choice in this case. The equipment had to be removed, and there is not sufficient room on the remaining Space Shuttle missions to return the tank to Earth. NASA’s Space Shuttle program is slated to end in 2010 after completing construction of the ISS.
Up to 15 pieces of the tank may survive reentry, with sizes ranging from ounces to nearly 40 pounds. The largest of these objects would be traveling at approximately 100 mph. At the time of this posting, the exact reentry time and place is uncertain. Paranoid persons or the extremely unlucky are advised to stay indoors or to wear a helmet.