Minimum estimates of the amount and timing of gases released into the martian atmosphere from volcanic eruptions

Abstract

Volcanism has been a major process during most of the geologic history of Mars. Based on data collected from terrestrial basaltic eruptions, we assume that the volatile content of martian lavas was typically ∼0.5 wt.% water, ∼0.7 wt.% carbon dioxide, ∼0.14 wt.% sulfur dioxide, and contained several other important volatile constituents. From the geologic record of volcanism on Mars we find that during the late Noachian and through the Amazonian volcanic degassing contributed ∼0.8 bar to the martian atmosphere. Because most of the outgassing consisted of greenhouse gases (i.e., CO 2 and SO 2) warmer surface temperatures resulting from volcanic eruptions may have been possible. Our estimates suggest that ∼1.1 × 10 21 g (∼8 ± 1 m m −2) of juvenile water were released by volcanism; slightly more than half the amount contained in the north polar cap and atmosphere. Estimates for released CO 2 (1.6 × 10 21 g) suggests that a large reservoir of carbon dioxide is adsorbed in the martian regolith or alternatively ∼300 cm cm −2 of carbonates may have formed, although these materials would not occur readily in the presence of excess SO 2. Up to ∼120 cm cm −2 (2.2 × 10 20 g) of acid rain (H 2SO 4) may have precipitated onto the martian surface as the result of SO 2 degassing. The hydrogen flux resulting from volcanic outgassing may help explain the martian atmospheric D/ H ratio. The amount of outgassed nitrogen (∼1.3 mbar) may also be capable of explaining the martian atmospheric 15N/ 14N ratio. Minor gas constituents (HF, HCl, and H 2S) could have formed hydroxyl salts on the surface resulting in the physical weathering of geologic materials. The amount of hydrogen fluoride emitted (1.82 × 10 18 g) could be capable of dissolving a global layer of quartz sand ∼5 mm thick, possibly explaining why this mineral has not been positively identified in spectral observations. The estimates of volcanic outgassing presented here will be useful in understanding how the martian atmosphere evolved over time.