Due to these mental disorders, the efficiency of astronauts' work is impaired; and sometimes they are brought back to Earth, incurring the expense of their mission being aborted. A Russian expedition to space in 1976 was returned to Earth after the cosmonauts reported a strong odor that resulted in a fear of fluid leakage; but after a thorough investigation, it became clear that there was no leakage or technical malfunction. It was concluded by NASA that the cosmonauts most likely had hallucinated the smell.