Extraterrestrial AtmospheresA Brief Overview

So far -

● Atmospheric composition● Vertical profile of Temperature and Pressure ● Albedo, Weather, and Climate change

○ on Earth

● Venus & Jupiter

Venus fact sheet

● Distance from Sun - 0.7 AU● Mean density ratio - 0.951● Surface gravity ratio - 0.905● Bond albedo* ratio - 2.94 (0.90/0.306)● Solar irradiance ratio - 1.911

● Orbital period - 224 days● Rotational period - 243 days

Reference : Fact sheet, Lunar & Planetary Science, NASA

Venus fact sheet● Surface pressure - 92 bars● Avg. Temperature - 737 K (surface)● Wind speeds

○ - 0.3 to 1.0 m/s on surface○ 90 m/s on the upper layers of the atmosphere

■ 113 m/s in tropical cyclone on earth■ 135 m/s in tornadoes

● Atmospheric composition (by vol)○ 96.5% CO2, 3.5% N2○ 150 SO2, 70 Ar, 20 H2O, 17 CO, 12 He, 7 Ne

Atmospheric transmission of Venus

Transmission spectrum of Venus as a transiting exoplanetEhrenreich et al. 2011, Astronomy & Astrophysics Journal

● Theoretical model with inputs from Venus Express.● Rayleigh scattering from CO2 at 70 km● Mie scattering from H2SO4 droplets at 70-90 km

atmospheric transmission - earth

windsVenus Express mission has helped distinguish between● Acoustic Waves● Inertia-gravity waves● Lamb waves● Surface waves

○ similar to those in the geostrophic regime● Centrifugal waves

○ special case of Rossby waves, arising from cyclostrophic balance

Peralta et al. 2014 (I) and Peralta et al. 2014 (II)

Superrotation

In order to explain superrotation on Venus -

● Yamamoto & Takahashi 2006, maintained by meridional circulation.

● Durand-Manterola 2010, driven by trans-terminator flow

Jupiter fact sheet● Mass of Jupiter - 0.09% M_sun● Solar irradiance ratio - 0.037● Blackbody temperature - 110.0 K● bond albedo ratio - 1.12 ● Atmospheric composition (by vol) -

○ 89.8% H2, 10.2 % He○ 3000 CH4, 260 NH3, 28 HD, 5.8 C2H6, 4 H2O

● Surface pressure >> 1000 bars● wind speeds

○ ~ 150 m/s at < 30 latitude○ ~ 40 m/s at > 30 latitude

Jupiter’s bands

Jupiter’s giant red spot

Jupiter’s giant red spotOn Earth● typical cyclone speeds

○ ~100 m/s● typical size of a cyclone

○ ~100-2000 kmJupiter’s giant red spot● speed near the edge

○ ~120 m/s● size of the cyclone

○ 20,000 km by 12,000 km

the spot is shrinking, albeit very slowly.

Hassanzadeh & Marcus 2013 studied the unexpected longevity of the giant red spot and attributed meridional circulation as the cause.

● can extract shear energy and energize the vortex

Similar to a previous method, to estimate the atmospheric transmission of Venus by observing it during transit, Tsumura, Arimatsu, Egami et al. 2014 observed the Jovian moons eclipsed in the Jovian shadow.

back to earth

● Climate change and how global warming raises the mean sea level

● Methane or carbon trapped in polar or glacial ice● Soot and how it changes the albedo of Earth

○ what happens to all of this soot?

Dark Snow project