Photochemical escape of oxygen from Mars: First results from MAVEN in situ data

摘要: Photochemical escape of atomic oxygen is thought to be one the dominant channels for Martian atmospheric loss today and played a potentially major role in climate evolution. MAVEN first mission capable measuring, situ, relevant quantities necessary calculate photochemical fluxes. We utilize 18 months data from three instruments: LPW, NGIMS STATIC. From these we altitude profiles production rate hot atoms dissociative recombination (DR) O2+ probability that such will Mars atmosphere. this determine fluxes 815 periapsis passes. Derived average dayside O rates range 1.2 5.5 x 1025 s-1 depending on season EUV flux, consistent with several pre-MAVEN predictions broad agreement estimates made other measurements. Hot do not vary significantly solar zenith angle or crustal magnetic field strength, but depend CO2 photoionization frequency power law whose exponent 2.6 ± 0.6, an unexpectedly high value which may partially due seasonal geographic sampling. dependence historical measurements over 70 years, estimate modern-era 4.3 1025 s-1. Extrapolating early system conditions gives total losses 13, 49, 189, 483 mb 1, 2, 3, 3.5 Gyr respectively, uncertainties increasing time past.