Past, present and future of the Venus exploration

(1)

D.V. Titov D.V. Titov

MPI for Solar System Research MPI for Solar System Research

Katlenburg

Katlenburg -Lindau - Lindau, Germany , Germany

Past, present and future of Past, present and future of the Venus exploration

the Venus exploration

(2)

1. History of the Venus exploration

(3)

(4)

Ancient views of Venus Ancient views of Venus

Babilon

Babilon: : Ishtar Ishtar - - the Mother of the the Mother of the God who invokes the power of dawn God who invokes the power of dawn

Maya:

Maya: Kukulcan Kukulcan - - the Sun the Sun ’s brother, ’ s brother, patron planet of warfare

patron planet of warfare Early Christians:

Early Christians: Lucifer Lucifer Greeks / Romans:

Greeks / Romans: Aphrodite / Venus Aphrodite / Venus

– – the goddess of beauty and love the goddess of beauty and love

(5)

Venus before the space era Venus before the space era

1610 – Galileo Galilei observed phases of Venus.

Early indication of that the planets rotate around the Sun not the Earth

Venus transits were used to determine distances in the Solar System

1761 - discovery of the

atmosphere by Lomonosov

(6)

Venus before the space era Venus before the space era

20-th century – the birth of spectroscopy

1920s - cloud top temperature of ~ 240K

1930s - CO

₂

composition, low H

₂

O abundance

1950s – radio

investigations: planet rotation, hot surface

Venus models: from Earth-like to hell-like

Venus surface according to S. Arrhenius

(7)

Who will be the first to Who will be the first to

reach Venus?

1960s – interplanetary spacecraft for Mars and Venus exploration was built by the Soviet Union. The first launch failed. The second one (12.02.1961) succeeded but

communication was lost.

1962 – Mariner -2 – first Venus fly-by and data returned

Venera- 1

Mariner-

2

(8)

Goal

Goal - - to reach the surface ! to reach the surface !

Venera

Venera - - 4, 5, 6 reached ~20 km 4, 5, 6 reached ~20 km Venera

Venera- -7 7 – – soft landing ! soft landing !

Venera- 4

Venera-

7

(9)

Second generation of the

Second generation of the Venera Venera spacecraft (1970 spacecraft (1970 -80) - 80)

(10)

Second generation of the

Second generation of the Venera Venera spacecraft (1970 spacecraft (1970 -80) - 80)

(11)

First panoramas First panoramas

Venera- 13

Venera- 14

Venera-

14

(12)

Pioneer Venus

Pioneer Venus multiprobe multiprobe mission (1978- mission (1978 -92) 92)

Atmospheric studies from orbit

In-situ investigations Plasma monitoring

Surface radar mapping

(13)

Zo na l

Zo na l su pe rr ot at io n su pe rr ot at io n

VEGA Balloons (1984)

(14)

Global network of balloon tracking stations

(15)

Venus unveiled

Venus unveiled … …

Venera-15-16

Pioneer- Venus

Magellan

(16)

Venus Express

Venus Express – – the first ESA the first ESA mission to Venus

mission to Venus

(17)

From Mars Express to Venus Express in 3 years From Mars Express to Venus Express in 3 years

Solar panels: smaller and different Solar panels: smaller and different composition

composition

Modified thermal design Modified thermal design

Accommodation of the new Accommodation of the new payloads

payloads

Smaller dish of the main antenna Smaller dish of the main antenna Second antenna

Second antenna

(18)

V1 launch, 1961

Venus Express launch,

2005

(19)

Souyz

Souyz launch #1703 launch #1703 November 9, 2005, November 9, 2005,

3:33:33 UTC 3:33:33 UTC

Arrival at Venus:

April 11, 2006

(20)

Venus Express payload Venus Express payload

•• VIRTISVIRTIS (P. Drossart, G. Piccioni) - UV-vis-near IR imaging and high resolution spectrometer (IPF/ DLR, MPS)(IPF/ DLR, MPS)

•• SPICAV / SOIRSPICAV / SOIR(J.-L. Bertaux, O. Korablev, P. Simon) -UV & IR spectrometer for solar/stellar occultations and nadir observations

•• PFSPFS (V. Formisano) - high resolution IR Fourier spectrometer (IPF/ DLR)(IPF/ DLR)

•• VMCVMC (W.J. Markiewicz) - Venus Monitoring Camera ( MPS, IPF/ DLR, IDA/ TU( MPS, IPF/ DLR, IDA/ TU-BS)-BS)

•

• VeRaVeRa (B. Häusler, M.Pätzold) - radio science experiment ((UniUni Bundeswehr, Bundeswehr, UniUni Koeln) Koeln)

•• ASPERAASPERA(S. Barabash) - Analyzer of Space Plasmas and Energetic Atoms (MPS)

(MPS)

•• MAG (T. Zhang) – Magnetometer (TUMAG (TU-- BS)BS)

(21)

T e le c o m m u n ic a ti o n s T e le c o m m u n ic a ti o n s

2 h

Apocentre 11 h Apocentre

mosaic mosaic

15 h 23 h

Off-p ericentreobservations

Pericentre

Pericentre observations observations

P P

Orbit and operations Orbit and operations

Polar orbit Polar orbit

Pericentre latitude 78 – 90 N Pericentre altitude 350 -175 km Apocentre altitude ~ 66,000 km Period ~ 24h

Observation modes Observation modes

nadir in pericentre

nadir at ascending arc apocentre mosaic

solar occultation

Earth radio-occultation

(22)

2. Venus in the Solar System

(23)

Venus as a Planet Venus as a Planet Radius = 6070 km (0.95 R Radius = 6070 km (0.95 R E E ) )

Mass = 0.815 M Mass = 0.815 M E E

Equator

Equator -to - to- -orbit inclination = 3 deg orbit inclination = 3 deg Distance to the Sun: 0.72

Distance to the Sun: 0.72 a.u a.u . . Solar flux = 2

Solar flux = 2 Earth Earth

(24)

Venus strange rotation

Sidereal Year 225 days

Sidereal Day 243 days (retrograde) Solar Day (sol) 117 days

365 d

225 d 243 d 1 d

Sun in the Venus sky

East West

(25)

3. Structure of the Atmosphere

(26)

Clouds Clouds

N ig ht D ay

Temperature structure Temperature structure

Thermosphere Thermosphere

Mesosphere Mesosphere

Troposphere Troposphere

VEX VEX

(27)

150 200 250 300 350 400 450 Temperature [K]

10⁵ 10⁴ 10³ 10² 10¹

Pressure [Pa]

DOY 122 2007 lat: - 7.5°

DOY 132 2007 lat: - 46.1°

DOY 142 2007 lat: - 77.3°

DOY 148 2007 lat: - 87.0°

Radio-occultation temperature profiles

76

65

A lt it u d e , k m

50 86

Cloud

Tellmann et al, JGR, 2009.

(28)

Radio-occultation temperature field

Tellmann et al, JGR, 2009

(29)

Static stability (VeRa)

low latitudes middle latitudes high latitudes

Tropopause

Tellmann et al, JGR, 2009

(30)

4. Atmospheric composition

(31)

CO CO

₂₂

- - 96,5% 96,5%

N N

₂₂

- - 3.5% 3.5%

H H

₂₂

O, CO, O, CO, SO SO

₂₂

, COS, , COS, HCl HCl , HF , HF … …

In situ measurements

(32)

Composition of the lower atmosphere by VIRTIS Composition of the lower atmosphere by VIRTIS

CO (36 km) : 24

CO (36 km) : 24 - - 31 ppm 31 ppm H H

₂₂

O (36 km) : 31 +/ O (36 km) : 31 +/ - - 2 2 ppm ppm COS (33 km) : 2.5

COS (33 km) : 2.5 - - 4 ppm 4 ppm

SO SO

₂₂

(33 km) : 130 +/- (33 km) : 130 +/ - 50 ppm 50 ppm

(33)

Mesospheric sounding in solar occultation

(34)

COSPAR, Montréal, July 15, 2008

SPICAV/SOIR solar occultation

To Sun

Venus

VEX

Atmosphere

Orbit 232 – Order 129

Cloud top

Bertaux et al.

(35)

COSPAR, Montréal, July 15, 2008

SPICAV/SOIR solar occultation

To Sun

Venus

VEX

Atmosphere

Orbit 232 – Order 129

Cloud top

150 km

65 km

Detected molecules:

CO CO

₂₂

, H , H

₂₂

O, HDO, CO, O, HDO, CO, HCl HCl , SO , SO

₂₂

Bertaux et al.

(36)

Examples

Examples of SOIR spectra of SOIR spectra

42650 4270 4275 4280 4285 4290 4295 4300 4305

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

tm20061224 - Order 191 - Slit 2

27000 2705 2710 2715 2720 2725 2730

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

tm20061224 - Order 121 - Slit 2

33250 3330 3335 3340 3345 3350 3355 3360

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

tm20061224 - Order 149 - Slit 1

38200 3825 3830 3835 3840 3845 3850 3855

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

tm20061224 - Order 171 - Slit 2

121 171

191 149

HDO

H

₂

O

CO

₂

(37)

Summary of composition results Summary of composition results

SO₂ CO

H 2 SO 4

H₂O

H₂O SO₂

Svedhem et al., Nature, 2007

(38)

70

Mesospheric Photochemical Mesospheric Photochemical

Factory Factory

Decrease of SO

₂

and H

₂

O abundance at the cloud tops Formation of H

₂

SO

₄

aerosols

Models do not explain observed amount of O

₂

Unknown UV absorber

Chlorine and sulfur chemistry in the Earth atmosphere CO

₂

H

₂

O

SO

₂

HCl

H

₂

SO

₄

CO

O 2

h

50

100

(39)

50

20

Chemistry of the lower Atmosphere Chemistry of the lower Atmosphere

Decomposition of H

₂₂

SO SO

₄₄

No photochemistry

High temperatures and pressure High temperatures and pressure

Chemical disequilibrium except very Chemical disequilibrium except very close to the surface

close to the surface

Buffering of the atmospheric compo Buffering of the atmospheric compo- - sition

sition by the surface by the surface Open questions Open questions

surface composition surface composition CO and O

CO and O

₂₂

at the surface at the surface too high SO

too high SO

₂₂

abundance abundance volcanism replenishes SO volcanism replenishes SO

₂₂

H H 2 2 SO SO 4 4

SO

₃

CO

H

₂

O COS

H

₂

SO

₄

→ SO

₃

+ H

₂

O

SO

₂

CO

₂

HCl HF

H

₂

O

CO 2 SO 2

CaCO

₃

SiO

₂

CaSO

₄

CaSiO

₃

(40)

Composition , %

0.035

~ 0

0.00005

~3 0.965 0.965 0.0001 H H

₂₂

SO SO

₄₄

+? +?

0.78 0.78 0.21 0.21

< 0.03

~3· ~3 ·10 10

⁵⁵

0.0003

~0 H H

₂₂

O O N

₂

O

₂

Atmospheric H

₂

O

Total H

₂

O, cm CO

₂

SO

₂

Clouds

+ 460 (!) + 460 (!) +15

Surface T, ° C

90 90 1

Surface P, bar

Venus Earth

So different twins

(41)

5. Greenhouse effect

(42)

Solar Solar

radiation radiation

Therma Therma l l

emissio emissio n n

Basics of the greenhouse effect Basics of the greenhouse effect

Wavelength, microns

10 µm

0.5 µm 1 µm 5 µm

(43)

Absorption bands of the atmospheric gases

(44)

Contribution of the atmospheric components to Contribution of the atmospheric components to

the greenhouse effect on Venus the greenhouse effect on Venus

Temperature, K

CO CO 2 2 – – 460K 460K H H 2 2 O – O – 220K 220K

Clouds

Clouds – – 100K 100K

H 2 SO 4 Clouds

CO 2 H 2 O

T T

_eff_eff

~250 K ~250 K Ts ~ 750 K Ts ~ 750 K

(45)

Greenhouse effect Greenhouse effect on terrestrial planets on terrestrial planets

Venus Venus – – 500K 500K

Mars

Mars – – 5K 5K

Earth

Earth – –

40K 40K

(46)

Greenhouse effect and water loss (1) Greenhouse effect and water loss (1)

Similar volatile inventories at origin Similar volatile inventories at origin

Present water amount: H

₂₂

O O

_VENUS_VENUS

~ 10 ~ 10

^-5^-⁵

H H

₂₂

O O

_EARTH_EARTH

Deuterium enrichment: (D/H)

_VENUS_VENUS

~ 150 (D/H) ~ 150 (D/H)

_EARTH_EARTH

(47)

Earth

Earth- -like planet: greenhouse effect and water loss (2) like planet: greenhouse effect and water loss (2)

Solar flux, W/m Solar flux, W/m

²²

T

_s

< 100 C T

_s

< 100 C T

_s

~ 100 C T

_s

>> 100 C 400 400

300 300 625 625

Venus now Venus now

Runaway

Runaway greenhouse greenhouse

Moist Moist greenhouse greenhouse

Earth now Earth now

Kasting, JGR, 1988

(48)

Greenhouse effect and habitability zone Greenhouse effect and habitability zone

MARS EARTH VENUS MERCURY

Distance, AU Distance, AU

1 0.72 0.39

1.52

Runaway greenhouse Runaway greenhouse Paradise

Paradise Global

Global

fridge

(49)

6. Non

6. Non - - LTE emissions LTE emissions

(50)

Origin of airglow on Venus

R. Hueso, private communication

(51)

7. Clouds and hazes

(52)

Venus Cloud Properties Venus Cloud Properties

Altitude range 75

Altitude range 75 – – 45 km 45 km Total opacity 20

Total opacity 20 - - 40 40 Visibility > 300 m Visibility > 300 m Particles:

Particles:

R = 1

R = 1- -10 10 m m N = 100

N = 100 -1000 cm - 1000 cm

^-3^-³

Composition:

H H

₂₂

SO SO

₄₄

+ ? ( + ? ( S S

_n_n

, AlCl , AlCl

₃₃

, H , H

₃₃

PO PO

₄₄

, , … … ) )

Aerosol extinction, km

^-1^-¹

(53)

Orbit #673

Orbit #679 Orbit #458

Orbit #462

Cloud morphology: Global UV view (VMC)

(54)

Cloud morphology

(55)

Close

Close - - up views up views

#1036

#1110 Orbit #920

#1024

Orbit #1121

#1095

(56)

Orbit #637 Orbit #722

Morning Evening

Cloud morphology: afternoon

Cloud morphology: afternoon vs vs morning morning

N ig h t s id e N ig h t s id e

(57)

Cloud top altitude Cloud top altitude

Ignatiev et al., JGR, 2009

1200 1600 2000 2400

Wavelength, nm 0

20 40 60 80

Radiance, W m-2 sr-1um-1

CO₂

(58)

Venus planetary vortex Venus planetary vortex

VMC UV (0.365 VMC UV (0.365 μ μm) m)

~ 70 km

VIRTIS IR (1.7 VIRTIS IR (1.7 μ μ m) m)

~ 50 km

(59)

Venus polar vortex and hurricane Frances Venus polar vortex and hurricane Frances

S. Limaye et al., GRL, 2009

(60)

8. Atmospheric dynamics

(61)

Global Circulation Regimes Global Circulation Regimes

Troposphere and mesosphere

Zonal superrotation (>100 m/s) Poleward winds v ~ 10 m/s

Thermosphere (> 120 km)

Zonal superrotation (~100 m/s) Solar-antisolar circulation

(~200 m/s)

So la r So la r - - an tis

ola an tis

ola r r

Z on al Z on al

su pe rr ot at io n

(62)

Super

Super - - rotation rotation

VMC VMC 70 km 70 km

50 km 50 km VIRTIS VIRTIS

Zonal wind, m/s

A lt it u d e , k m

(63)

Latitude, deg

0 -30 -60 -90

50 km 50 km 60 km 60 km 70 km

Z o n a l w in d s p e e d , m /s

0 -120

-80

-40 Vertical wind sheer

Vertical wind sheer 2 2 - - 3 3 m/s m/s per km per km

No wind No wind

sheer sheer

Almost solid Almost solid body rotation body rotation Zonal wind field

Zonal wind field

Sanches-Lavega et al., GRL, 2008

(64)

T tan

R u u

2

Piccialli

Piccialli et al., PhD Thesis, 2009et al., PhD Thesis, 2009

Thermal (

Thermal ( cyclostrophic cyclostrophic ) wind from ) wind from Radio

Radio - - occultation occultation

VMC UV VMC UV

VIRTIS IR

(65)

Eye of the polar vortex Eye of the polar vortex

Piccioni, Drossart

(66)

Waves in polar region (65

Waves in polar region (65- -70 N) 70 N)

(67)

Waves in polar region (65

Waves in polar region (65 - - 70 N) (VMC) 70 N) (VMC)

UV

NIR

50 km

(68)

9. 9. Radiative Radiative energy balance energy balance

(69)

Composite spectrum of the outgoing radiation Composite spectrum of the outgoing radiation

Thermal IR from the cloud tops Solar reflected

Lower atmosphere emissions

T = 230-250 K Solar flux at the top of

the Venus atmosphere

E ~ 2600 W/m

²

(70)

Venus gets less energy than Venus gets less energy than the Earth !

the Earth !

Net heating at equator, net Net heating at equator, net cooling on poles

cooling on poles

Latitudinal distribution of Latitudinal distribution of radiative

radiative balance implies balance implies

energy transport by circulation energy transport by circulation

Latitude

R a d ia ti v e fl u x

Venus

Earth Received from the Sun Received from the Sun

Emitted to space Emitted to space

Taylor et al., Adv. Space Res, 1982

Latitudinal distribution of energy sources and sinks

(71)

Vertical distribution of deposited solar energy Vertical distribution of deposited solar energy

Ekonomov et al., Venus-1 book,1983

Venera-13

(72)

Global mean heating Global mean heating

and cooling rates and cooling rates

Solar heating Thermal

cooling

Tomasko et al., Adv. Space Res, 1985 Crisp & Titov, Venus-2 book, 1997

half of solar energy half of solar energy deposited on Venus is deposited on Venus is

absorbed by the unknown absorbed by the unknown UV absorber in the cloud UV absorber in the cloud layer

layer

(73)

Mean deposition of solar energy on Mean deposition of solar energy on

terrestrial planets [ W/m terrestrial planets [ W/m

²²

] ]

125 170

20 Surface

~0 70

130 Atmosphere

Mars Earth

Venus

(74)

Atmospheres as heat engines Atmospheres as heat engines

Energy transport by atmospheric motions Dissipation due to friction

Efficiency

T T 1 1

T T 2 2 1

1 2

T

(75)

10. Entropy balance

(76)

Planetary balance of

Planetary balance of radiative radiative energy and entropy energy and entropy Energy balance:

E

_Solar

– E

_ThIR

= 0 Entropy:

S = E/T 2-d Law of

Thermodynamics:

S ≥ 0

=0 - reversible processes

>0 – irreversible processes

Entropy is a measure of

dissipative processes

(77)

Flux of

Flux of radiative radiative entropy entropy No atmosphere

T T

_S_S

S = E/T

_S

– E/T

_S

= 0

Dense atmosphere

T T

_S_S

T(z T(z ) )

T T

_C_C

< T < T

_S_S

S = E/T E/T

_S_S

– E/T

_C

< 0

Planets receive negative entropy from the Sun

(78)

70

50

0

Solar

625 475

100 / 400

Thermal

Cloud (250 K)

Surface (735K)

150 / 600

Lower atmosphere (400K) 30 / 75

20 / 27

Radiative Radiative

Energy / Entropy Energy / Entropy balance on Venus balance on Venus

Radiative

Radiative energy balance energy balance E ≈ E ≈ 0 0

Radiative

Radiative entropy balance entropy balance

S ≈ S ≈ - - 100 mW/m 100 mW/m

²²

/K /K

(79)

Entropy balance on Earth and Venus Entropy balance on Earth and Venus

-100 - 100 -3 - 3

Net balance Net balance

~1 ~1 +12 +12

Mechanical Mechanical

dissipation dissipation

0 0 +55 +55

Moist Moist

convection convection

-100 - 100 -70 - 70

Net radiative Net radiative sink sink

Venus Earth (Goody,

2000)

Dissipative processes in the Venus atmosphere

Dissipative processes in the Venus atmosphere - - ???? ????

(80)

Equilibrium and non

Equilibrium and non - - equilibrium thermodynamics equilibrium thermodynamics

Time

E n tr o p y

Order Order

Chaos Chaos

T

₁

T

₂

E n tr o p y

Time Chaos

Chaos

Order

(81)

T

1

> T

2

critical temperature gradient critical temperature gradient high level of order

high level of order

high entropy production high entropy production

Benard convection

Non Non - - equilibrium dissipative systems equilibrium dissipative systems

Venus atmosphere Venus atmosphere – –

a non

a non - - equilibrium equilibrium dissipative system?

dissipative system?

(82)

11. Plasma investigations

(83)

Plasma Plasma environment environment (ASPERA & MAG) (ASPERA & MAG)

B e

^-

i

⁺

BS

Magnetosheath

BS

SW SW

IP IP IP IP

Induced Magnetosphere

From Brace & Kliore

(84)

Ion escape (ASPERA)

Energy- mass matrix in the plasma sheet

Spatial distribution of escaping O

⁺

• • Escaping ions: H Escaping ions: H

⁺⁺

, He , He

⁺⁺

, O , O

⁺⁺

• • Energy ratio O Energy ratio O

⁺⁺

: He : He

⁺⁺

: H : H

⁺⁺

~ 4:2:1 ~ 4:2:1 ion pick

ion pick- -up up

• • Flux ratio Flux ratio H H

⁺⁺

:O :O

⁺⁺

~ 2:1 ~ 2:1 H H

₂₂

O O

• • Escape occurs though the Escape occurs though the plasma sheet and induced plasma sheet and induced magnetosphere boundary magnetosphere boundary

Barabash et al., Nature, 2007

(85)

10^-2 ^{2 3 4 567}10^-1 ^{2 3 4 567}10⁰ ^{2 3 4 567}10¹ electron density (10¹¹ el/m³)

75 125 175 225 275 325 375

altitude (km)

DOY 196, X = 50°, lat = -5°

DOY 200, X = 56°, lat = -25°

DOY 202, X = 59°, lat = -34°

DOY 212, X = 80°, lat = -73°

DOY Lat[ ] SZA[ ]

□ 196 -5 50

◊ 200 -25 56

○ 202 -34 59 212 -73 80

Structure of the ionosphere (VeRa)

Pätzold et al., Nature, 2007

(86)

309 km altitude, 0516 LT, 85^olatitude

Detection of lightning (MAG)

Russell et al., Nature, 2007

(87)

12. Surface

(88)

Venus unveiled

Venus unveiled … …

Venera-15-16

Pioneer- Venus

Magellan

(89)

Surface panoramas by

Surface panoramas by Veneras Veneras

Venera- 13

Venera- 14

Venera-

14

(90)

Venus surface with VIRTIS on VEX > J. Helbert > LaThuile 2008 Folie 90

VMC mosaic

(91)

Venus surface with VIRTIS on VEX > J. Helbert > LaThuile 2008 Folie 91

Surface flux anomalies (VIRTIS) Surface flux anomalies (VIRTIS)

Alpha Regio

Dolya Tessera Phoebe Regio

Cocomama Tessera Tyche Tessera

Lhamo Tessera

N. Mueller et al., JGR, 200

N. Mueller et al., JGR, 2008 8

(92)

Future studies Future studies

Mission is extended till the end of 2012 Venus Express: atmospheric drag experiment and aerobraking

Joint observations with the Japanese orbiter mission Akatsuki (2011-12)

Future in-situ missions (landers,

balloons)

(93)

Conclusions Conclusions

About 2 Tbits of data are collected in > 3 years Venus Express delivers global and detailed survey of the atmospheric and plasma properties and processes

We are on the way to understanding how the processes led to so different planet

Revival of the interest to Venus in science community and Space Agencies

Main problem – the lack of science resources

(94)

Coordinated VEX

Coordinated VEX -Planet - Planet -C observations - C observations

Simultaneous observations of cloud Simultaneous observations of cloud morphology

morphology

Complementary dynamics studies Complementary dynamics studies Joint airglow observations

Joint airglow observations Complementary radio

Complementary radio- -science science investigations

investigations

(95)

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