Welcome to Venus!Home of the solar system’s most massive atmosphere

Michael Hammer

Welcome to Venus!Home of the solar system’s most massive atmosphere

Michael Hammer

Welcome to Venus:Home of the solar system’s most massive atmosphere

Michael Hammer

Venus Express

Properties of Venus

Missions to Venus

[1] 1962: Mariner 2 (flyby)

(that didn’t mess up completely)

[2] 1967, 1973: Mariner 5, 10 (flybys)[3] 1969 – 83: Venera 5 – 16 (Entered Atmosphere!)[4] 1978: Pioneer (Entered Atmosphere!)

[6] 1989: Magellan (orbiter)[5] 1984: Vega (Entered Atmosphere!)

[7] 2005: Venus Express (orbiter)[8] 2010: Akatsuki (orbiter)2015:[9] 2025: Venera-D (Will Enter Atmosphere!)[9] 2021: Da Vinci (Would Enter Atmosphere!)

Effective Temperature

Venus is probably too cold to support life.

Temperature Profile

Actually, Venus is really hot!

1 bar

90 bars

Temperature Profile(compared to Earth)

Similar to Earth ( below 1 bar )

Temperature Profile: Dry Lapse Rate

Composition

CO2: 96.5% N2: 3.5%

Venus’s atmosphere is 100 times more massive than Earth’s atmosphere.

(Remember the surface pressure of 92 bars!)

SO2:150 ppmAr: 70 ppmCO: 40 ppmH2O: 30 ppm

All measured withPioneer “gas chromatograph” in 1980.

3ν3 line (2.45 μm) at night!

J = 2 à 0 line (2.30 μm) at night!

Ground-based NIR sounding.

Composition: Lots of CO2 (and N2 too)

CO2: 96.5% N2: 3.5%

Note 1: Each percent is one Earth’s atmosphere.

SO2:150 ppmAr: 70 ppmCO: 40 ppmH2O: 30 ppm

All measured withPioneer “gas chromatograph” in 1980.

Over three times as much N2as in Earth’s atmosphere!!!

Note 2: 100 ppm is 1% of the Earth’s atmosphere.

How is there so much CO2?

Earth used to have a CO2 – rich atmosphere, but…

H2OCO2 Rocks+ =e.g. carbonatessuch as CaCO3

(dissolved in oceans)

Venus had no oceans. Thus, its CO2 stayed gaseous.

Why is Venus so hot?

The atmosphere is very massive.This makes the planet very opaque!

Venus’s clouds make things worse.

CO2 absorption lines at IR wavelengthsalso make things worse.

The atmosphere is very massive.This makes the planet very opaque!

Clouds

The entire planet is covered in clouds!

CloudsThree layers of clouds

(47 to 70 km)

Upper layers (made of hydrated sulfuric acid)

give Venus its yellow color.

Lowest layer is the thickest

(made of volcanic ash).It features individual

clouds like Earth.

Clouds: Formation Processes

This is the one of the things we actually understand about Venus!

Dynamics: Super Winds!

Venus has super winds!They travel 60x faster than the rotation of the planet,

(hence the name: “super-rotation”)

Dynamics: Super-rotation!

Rotation Speed of Planet:

Max Wind Speed (at 90 km – top of the cloud layers):

Models cannot explain how Venus has super-rotation!

Dynamics: General Circulation(Hadley Cells)

If we observed stronger Hadley cells on Venus,we could explain its super-rotating winds.

(But we don’t, so we still can’t…)

Venus’ atmosphere is 100 times more massive than the Earth’s atmosphere.

Conclusions

The mass of the atmosphere and the omnipresent clouds make Venus’s surface very hot.

Venus has super-rotating winds that are not understood. They may be caused by (1) north-south circulation,

(2) the slow day-night cycle,or (3) gravity waves generated near mountains.

The entire planet is covered with clouds that are made of sulfuric acid (upper) and volcanic ash (lower).