Geography 441/541 S/16 Dr. Christine M. Rodrigue Mars' Atmosphere Geography 441/541 S/16 Dr. Christine M. Rodrigue C.M. Rodrigue, 2016 Geography, CSULB

Mars' Atmosphere Mars' atmosphere, weather, and climate Chemical composition and dustiness Vertical temperature and pressure structure Horizontal pressure structure Winds and the global circulation Martian weather: Seasonality Storms Mars climate: Geochemical cycles and weather Climate zones Climate change C.M. Rodrigue, 2016 Geography, CSULB

Mars' Atmosphere Atmospheric gas composition: Earth dominated by Molecular nitrogen (78%) Molecular oxygen (21%) Variable amounts of water Trace amounts of carbon dioxide (0.04%), argon (0.93%), various others Mars dominated by Carbon dioxide (95%) Molecular nitrogen (2.7%) Argon (1.6%) Trace amounts of oxygen, carbon monoxide, water vapor, hydrogen C.M. Rodrigue, 2016 Geography, CSULB

Mars' Atmosphere Atmospheric density (p) and altitude (A): Declines with altitude, as on Earth Less atmosphere above compressing air Mars lapse is less steep than Earth's p = 0.699 * e -0.00009 * A (Mars) vs. p = 101.325 * e -0.00012 * A (Earth) p (kPa); A (m) C.M. Rodrigue, 2016 Geography, CSULB

Mars' Atmosphere Vertical temperature structure Temperature behavior with altitude defines bands, as on Earth Less atmosphere above compressing air C.M. Rodrigue, 2016 Geography, CSULB

Mars' Atmosphere Hadley cell: O2 & NO glow 1.27 μm emission (NIR) ESA MEX OMEGA C.M. Rodrigue, 2016 Geography, CSULB

Mars' Atmosphere Spatial variations in air pressure: Hadley circulation: temperature + Coriolis force (Wikipedia image) C.M. Rodrigue, 2016 Geography, CSULB

Mars' Atmosphere Spatial variations in air pressure: Hadley circulation: temperature + Coriolis force Uplift at equator → low pressure Air subsides ~45° → higher pressure Like Earth around equinoces: 2 cells Unlike Earth around solstices: 1 big cell C.M. Rodrigue, 2016 Geography, CSULB

Mars' Atmosphere Spatial variations in air pressure: Hadley circulation: temperature + Coriolis force Uplift at equator → low pressure Air subsides ~45° → higher pressure Like Earth around equinoces: 2 cells Unlike Earth around solstices: 1 big cell C.M. Rodrigue, 2016 Geography, CSULB

Mars' Atmosphere Spatial variations in air pressure: Hadley circulation: temperature + Coriolis force Equinox and solstice C.M. Rodrigue, 2016 Geography, CSULB

Martian Weather Temporal variations: Polar cyclones: Resemble Earth polar hurricanes Earth to right, Mars below C.M. Rodrigue, 2016 Geography, CSULB

Martian Weather Temporal variations: Air pressure changes Diurnal patterns (Pathfinder) Midday spike, sundown pit Note odd peak around midnight and "wee hours" drop Complex secondary pattern, with as many as 4 pits and peaks C.M. Rodrigue, 2016 Geography, CSULB

Martian Weather Temporal variations: Air pressure changes Diurnal patterns MRO Climate Sounder confirmed Pathfinder data Found it is global More pronounced away from equator Thermal tide creates lows under late afternoon sun C.M. Rodrigue, 2016 Geography, CSULB

Martian Weather Temporal variations: Air pressure changes Diurnal patterns Thermal tide inverse relationship to pressure tide These create local winds C.M. Rodrigue, 2016 Geography, CSULB

Martian Weather Temporal variations: Air pressure changes Seasonal patterns Annual cycles of pressure changes Huge increase as South Polar ice cap sublimes and starts moving to North Pole Reverse blip from smaller North Pole effect C.M. Rodrigue, 2016 Geography, CSULB

Mars' Climates Temporal variations: Length of seasons Unequal (Earth's close to equal in length) Mars' greater eccentricity C.M. Rodrigue, 2016 Geography, CSULB

Mars' Climates Temporal variations: Thermal inertia Some materials heat up/cool down quickly (like land surfaces on Earth) Low specific heat/thermal inertia This affects diurnal and seasonal temperature contrasts, pressure differences, and winds/breezes: land-and-sea breezes, monsoons On Mars, high albedo regions (dusty) have low thermal inertia and function like "continents" or inland areas on Earth Others heat up/cool slowly (like ocean/lake surfaces on Earth) High specific heat/thermal inertia On Mars, low albedo surfaces tend to have high thermal inertia and function like "water bodies" on Earth climatologically C.M. Rodrigue, 2016 Geography, CSULB

Mars' Climates Temporal variations in pressure and wind and spatial variations in albedo C.M. Rodrigue, 2016 Geography, CSULB

Mars' Climates Temporal variations in global circulation: S. summer C.M. Rodrigue, 2016 Geography, CSULB

Mars' Climates Temporal variations in global circulation: morning at 0° C.M. Rodrigue, 2016 Geography, CSULB

Mars' Climates Temporal variations in global circulation: afternoon at 0° C.M. Rodrigue, 2016 Geography, CSULB

Mars' Climates Temporal variations in global circulation: evening at 0° C.M. Rodrigue, 2016 Geography, CSULB

Mars' Climates Cloudiness: Carbon dioxide and water vapor Pathfinder below Phoenix to right C.M. Rodrigue, 2016 Geography, CSULB

Mars' Climates Storms: Dust storms (Hubble) and dust devils (Spirit in Gusev Crater) C.M. Rodrigue, 2016 Geography, CSULB

Mars' Climate Change Polar ice cap accelerated sublimation C.M. Rodrigue, 2016 Geography, CSULB

Mars' Climates Water and nitrogen cycle: Triple point 15N vs. 14N ratio high Mars lost 90% of its N Imagining it all back in the atmosphere, we get air pressure ~78 hPa That would have allowed liquid water Similarly, deuterium to hydrogen ratio high, ~7-8 x as high as Earth's Mars must have lost 6.5 times as much water as there is in the modern ice caps! C.M. Rodrigue, 2016 Geography, CSULB