Editor's note: Some readers may be disturbed by the content of this article, which refers to Air France Flight 447 and contains descriptions of human remains.
On Tuesday, Brazilian authorities recovered 16 bodies from the Air France crash in the Atlantic Ocean, bringing the total to 24.
The Airbus 330 jet took off from Rio de Janeiro on its way to Paris on May 31 when it disappeared during intense thunderstorms. Investigators are currently considering the possibility that the plane's airspeed sensors were iced over. Meanwhile the Brazilian navy is conducting an all-out search for the bodies.
Finding survivors lost at sea is a race against time because of the possibility of starvation or hypothermia. But none of the 228 people on board Flight 447 were expected to have survived the plane's impact.
So how long can a body remain intact at sea, to be recovered?
The Australian Museum has an informative Web site, deathonline.net, on how human remains change after death. On land, bacteria and other microbes in the body will rapidly multiply and break down the soft tissue. Shortly after death, flies and other insects consume the soft tissue. Vultures, dogs or other large mammals may also take pieces of the decomposing flesh, sometimes reducing the corpse into a skeleton in under two weeks.
On the open ocean, however, flies and other insects are largely absent. And if the body is floating in water less than 70 degrees Fahrenheit (21 degrees Celsius) for about three weeks, the tissues turn into a soapy fatty acid known as "grave wax" that halts bacterial growth. The skin, however, will still blister and turn greenish black. Finally, crabs and small fish may feed on the soft parts of the face like the eyes and lips, according to the book Forensic Taphonomy: The Postmortem Fate of Human Remains, by William D. Haglund and Marcella H. Sorg.
A 2002 study in the journal Legal Medicine examined nine bodies that had drifted hundreds of kilometers in cold waters off the coast of Portugal and Spain. Bodies recovered in the first week were in good condition, but the beginning signs of decomposition were present on a body recovered after eight days. The two bodies recovered after 20 days were highly decomposed and could only be identified through DNA analysis or dental records. As for warmer water, A 2008 study on two human bodies recovered following aircraft accidents found one body off of Sicily to be partially skeletonized after 34 days and a second body off of Namibia to be completely skeletonized after three months.*
Of course, sharks are an important scavenger in warm waters, like those off of Brazil, and can quickly reduce a body to shreds. "Sharks, like any predator, are opportunistic feeders, and they'll take advantage of a resource that's given to them," says George Burgess, director of the Florida Program for Shark Research at the Florida Museum of Natural History in Gainesville and the curator of the International Shark Attack File.
Low-frequency noises caused by a ship sinking or a plane crashing travel great distances underwater and can attract the animals. However, he says, "The idea that the…[seas]…are carpeted with sharks…is a misconception."
*UPDATE (6/11/09): In response to the comment by AndrewJayPollack, we have added this paragraph on the time frame of decomposition.
Image of waves breaking on a beach courtesy Mr.Thomas via Flickr