Argon in the Martian atmosphere: Evidence from the Mars 6 descent module

Mass spectrometry in the exploration of Mars

“…It is clear from these results that the N 2 content is consistent with earlier limits (3) and corroborates the results of the upper atmosphere analysis (5) performed during the descent of the Viking 1 lander. The argon content is much lower than most recently suggested (6) and again supports the value found for the upper atmosphere (5).…”

“…The mixing ratio for the gas at this altitude, relative to CO 2 , is approximately 0.015 by volume, in major disagreement with an indirect measurement of Ar inferred from data obtained by the Soviet probe Mars 6. Istomin and Grechnev (3) reported a mixing ratio of 0.54 ± 0.2 for an inert constituent of the martian atmosphere which they attributed to Ar. The mixing ratio of 40 Ar in the lower martian atmosphere cannot be this high and must lie somewhere in the range 0.01 to 0.02.…”

“…The noble gases provide a particularly useful measure of the degree of planetary outgassing. The report by Istomin and Grechnev (6) that the martian atmosphere might contain as much as 35 percent 40 Ar was widely interpreted to indicate that Mars had outgassed as thoroughly as Earth, and led to the prediction that massive amounts of concurrently produced volatiles had either escaped from the planet or were presently buried in the regolith (8). The discovery that the 40 Ar abundance is only 1 to 2 percent of the present atmosphere indicates that the other volatiles should be proportionately reduced in such models.…”

Model calculation of production rates, ion and electron densities in the evening troposphere of Mars at latitudes 67°N and 62°S: Seasonal variability

“…An upper limit of 0.5 to 5% of N 2 was reported from Mariner 6 and 7 measurements [ Dalgarno and McElroy , 1970]. Mars 6 measurements seemed to indicate that as much as 35% of the atmosphere might be a noble gas [ Istomin and Grechnev , 1976]. Finally, Viking Lander verified the presence of nitrogen and argon [ Nier et al , 1976; Owen and Biemann , 1976].…”

Martian permafrost features

“…Many estimates have been made of the amount of water outgassed from the planet . Some of the pre-Viking estimates are'based on an erroneously high value (35 + 10%) for argon in the Martian atmosphere inferred from anomalous ion pump readings on Mars 6 [lstomin and Grechnev, 1976]. Viking results indicate that the Martian atmosphere contains only 1-2% argon and that the 36Ar/4øAr ratio is a factor of 10 lower than in the earth's atmosphere .…”