Interplanetary dust particles accrete on the Earth at a rate of ~40 ktons yr-1. Some 90% of this material evaporates in the atmosphere, producing a bioavailable iron flux of 3¿10-7molFem-2yr-1. This extraterrestrial Fe flux is 30--300% of the eolian flux of bioavailable iron transported from terrestrial sources in remote marine regions and ~20% of the upwelled Fe flux in the Southern Ocean. Extraterrestrial Fe may play an important role in regulating the marine carbon cycle in these regions. ¿ 2001 American Geophysical Union