Question

How far up (to what altitude) in earth's atmosphere have living organisms been detected?

Crucial prerequisites for life include the presence of water and the availability of space--both present in the earth’s atmosphere. However, the region hosting the microbes must also contain nutrients such as carbon, nitrogen, phosphorous and various trace metals that microorganisms need to synthesize their cellular constituents. The environment also has to offer some form of fuel to provide the energy required for this ongoing activity (see http://www.sciam.com/1096issue/1096onstott.html). So far, microorganisms have been found 1.7 miles underground, but it is not clear how high up in the atmosphere they can live. Nevertheless, there have been bird strikes with aircraft in the 20-30,000 foot altitudes, and one could guess that microorganisms could be carried up to somewhere above 50,000 feet by vertical atmospheric motion. As an interesting sidenote, the SOFIA project may be the closest thing to searching for life while in orbit. SOFIA (the Stratospheric Observatory for Infrared Astronomy), is a Boeing 747SP aircraft modified to accommodate a 2.5 meter reflecting telescope, making it the largest airborne astronomical observatory in the world. The plane will cruise 41,000 feet above the ground, enabling it to observe incoming infrared energy that would otherwise be absorbed by the earth’s atmosphere at lower altitudes. For more information on the SOFIA project, see http://sofia.arc.nasa.gov
May 1, 2002