Abstract
The composition of the martian atmosphere was determined by the mass spectrometer in the molecular analysis experiment. The presence of argon and nitrogen was confirmed and a value of 1 to 2750 ± 500 for the ratio of argon-36 to argon-40 was established. A preliminary interpretation of these results suggests that Mars had a slightly more massive atmosphere in the past, but that much less total outgassing has occurred on Mars than on Earth.