First measurement of helium on Mars: Implications for the problem of radiogenic gases on the terrestrial planets

Details First measurement of helium on Mars: Implications for the problem of radiogenic gases on the terrestrial planets First measurement of helium on Mars: Implications for the problem of radiogenic gases on the terrestrial planets

Mar 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994lpi....25..749b&link_type=abstract

In Lunar and Planetary Inst., The Twenty-Fifth Lunar and Planetary Science Conference. Part 2: H-O p 749-750 (SEE N94-36136 11-9

Physics

Airglow, Atmospheric Models, Electron Impact, Exosphere, Helium, Ionization, Lower Atmosphere, Mars Atmosphere, Mixing Ratios, Photons, Radiative Transfer, Radiogenic Materials, Argon Isotopes, Atmospheric Chemistry, Charge Exchange, Degassing, Extreme Ultraviolet Explorer Satellite, Mass Ratios, Outgassing, Oxygen Atoms, Solar Wind

Scientific paper

The 108 photons of the Martian He 584 A airglow detected by the Extreme Ultraviolet Explorer satellite during a two-day exposure (22-23 Jan. 1993) correspond to the effective disk average intensity of 43 (+/-) 10 Rayleigh. Radiative transfer calculations, using a model atmosphere appropriate to the conditions of the observation and having an exospheric temperature of 210 (+/-) 20 K, result in an He mixing ratio of 1.1 (+/-) 0.4 ppm in the lower atmosphere. Nonthermal escape of helium is due to the following: electron impact ionization and pickup of He(+) by the solar wind; collisions with hot oxygen atoms; and charge exchange with molecular species with corresponding column loss rates of 1.4 x 105, 3 x 104, and 7 x 103 cm-2s-1, respectively. The lifetime of helium on Mars is 5 x 104 yr. The He outgassing rate, coupled with the Ar-40 atmospheric abundance and with the K:U:Th ratio measured in the surface rocks, is used as input to a simple two-reservoir degassing model which presumes the loss of all argon accumulated in the atmosphere during the first Byr by large-scale impacts. The model results in total planet mass ratios of 10-5 g/g for K, 2.3 x 10-9 g/g for U, 8.5 x 10-9 g/g for Th, 4 x 10-10 g/g for He, and 1.5 x 10-9 g/g for Ar-40. The predicted radiogenic heat flux is 2 erg cm-2s-1. Similar modeling for Venus results in total plant mass ratios of 4.7 x 10-5 g/g for K, 6.7 x 10-9 g/g for U, 2.2 x 10-8 g/g for Th, 1.3 x 10-9 for He, 6.7 x 10-9 g/g for Ar-40, and a radiogenic heat flux of 15 erg cm-2s-1. The implications of these results are discussed. The modeling shows that the radioactive elements were not distributed uniformly in the protoplanetary nebula, and their relative abundances differ very much in the terrestrial planets.

Affiliated with

Also associated with

No associations

Rating

First measurement of helium on Mars: Implications for the problem of radiogenic gases on the terrestrial planets does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with First measurement of helium on Mars: Implications for the problem of radiogenic gases on the terrestrial planets, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and First measurement of helium on Mars: Implications for the problem of radiogenic gases on the terrestrial planets will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1583001