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Gerard Wilkinson
5 years ago
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1 !!!!!!!! "#$%&!'! Lecture material: ()*+,!-.-/01!023*),+4)5!6),!7580,-/+5895:! /;0!;+<9/+<9*9/.!95!/;0!759=0,-0! 3,)?0--0-!+58!/;0!B+.!)6!,0-7*/+5/!89C0,054+4)5!)6!/;0! 3*+50/-!95/)!89C0,05/!B),*8-A!! D9-/),9?+**.E!-)*+,!-.-/01!023*),+4)5!;+-!<005!*08!<.!F(E! G7--9+!+58!%7,)30A!&)B!)/;0,!?)75/,90-!HI+3+5E!J589+E!K;95+'! +,0!+*-)!B),L95:!)5!9/!02/05-9=0*.A!! #!;7:0!571<0,!)6!02/,+-)*+,!3*+50/-!H02)3*+50/-'!;+=0!<005! 89-?)=0,08A!D+<9/+<9*9/.!)6!/;)-0!3*+50/+,.!-.-/01-!9-!+*-)!+! 1+M),!-?9054N?!95/0,0-/A!()*+,!-.-/01!023*),+4)5!+*-)!:9=0-!?*70-!/)!/;0!?)5894)5-!)6!02)3*+50/-A!!

2 ! O)33*0,!10/;)8! O0/0?4)5!10/;)8-!! >,+5-9/!10/;)8!! O9,0?/!91+:95:! Kepler 6b photometry D+<9/+<*0!P)50! Gliese !

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surface! Similar to the stratospheric aerosol layer of the Earth, but much thicker!

As a result, Venus absorbs solar energy much less than the Earth does. This explains the low temperature of the clouds.

4 Clouds of Venus! Highly-reflective, sulfuric acid droplets (H 2 SO 4 -H 2 O) floating around 60 km altitude and covering the whole surface! Similar to the stratospheric aerosol layer of the Earth, but much thicker! They turn 80% of the incoming solar radiation away. (Earth s atmosphere reflects 30% of solar radiation)! As a result, Venus absorbs solar energy much less than the Earth does. This explains the low temperature of the clouds. Solar energy available below the clouds Altitude (km) Clouds! Most of the solar energy absorbed by Venus is absorbed by clouds at high altitudes.! The solar energy which reaches the Venus surface is 10 times less than the solar energy at the Earth s surface. Net flux (W/m 2 )

! The surface of Venus is as hot as 460 C! Why can it be so hot?

obtained by Pioneer Venus lander Image of Venus surface taken by Russia s Venera 13 lander

Solar radiation Infrared radiation Planet Repeated absorption and emission Penetrate the

5 ! The surface of Venus is as hot as 460 C! Why can it be so hot?! Answer : Greenhouse effect Altitude (km) Clouds Height distribution of temperature obtained by Pioneer Venus lander Image of Venus surface taken by Russia s Venera 13 lander 460 C Temperature (K) Greenhouse effect Absorbed solar energy = Outgoing infrared energy Solar radiation Infrared radiation Planet Repeated absorption and emission Penetrate the atmosphere Surface Absorption and emission of infrared radiation by greenhouse gases (CO 2, H 2 O,..) raise the near-surface temperature.

(1 - A) S " a 2 4 " a 2 # T 4 T 4 " a 2 # T S4 4 " a 2 # T 4 T S (1 - A) S " a 2 4 " a 2 # T 4 (1 - A) S " a 2 + 4 " a 2 # T 4 4 " a 2 # T S4 T S 4 $2 x T = 1.

6 (1 - A) S " a 2 4 " a 2 # T 4 T 4 " a 2 # T S4 4 " a 2 # T 4 T S (1 - A) S " a 2 4 " a 2 # T 4 (1 - A) S " a " a 2 # T 4 4 " a 2 # T S4 T S 4 $2 x T = 1.19 T T T S Image provided by ESA Dense CO 2 atmosphere of Venus! The density of Venus atmosphere is 60 kg/m 3 near the surface. (The density of Earth atmosphere is 1 kg/m 3 ) Due to this massive atmosphere the surface pressure is equivalent 900 m deep in the ocean.! The bulk of the Venus atmosphere (96%) is CO 2. (Earth s atmosphere contains only 0.03% of CO 2 )! The dense CO 2 traps thermal radiation very effectively and causes a hostile environment near the surface.

Thin CO 2 atmosphere of Mars! Mars atmosphere is also mostly CO 2 (95%), but its density is 10000 times less than Venus s. The warming due to greenhouse effect is as small as several degrees.

7 Thin CO 2 atmosphere of Mars! Mars atmosphere is also mostly CO 2 (95%), but its density is times less than Venus s. The warming due to greenhouse effect is as small as several degrees.! The long distance to the sun results in a low temperature of -60 C. Moderate greenhouse effect on the Earth! In the absence of greenhouse effect the Earth atmosphere would be as cold as -20 C and the ocean would freeze over.! In reality a small amount of CO 2 and water vapor in the atmosphere provide greenhouse effect and raise the temperature to +15 C. The Earth ocean would freeze if CO 2 is absent.! Moderate greenhouse effect is indispensable to life.

8 Energy budget and temperature Solar flux [W/m 2 ] Albedo (Reflecti vity) Absorbed energy [W/ m 2 ] Greenhouse effect No Yes Venus Earth Mars CO 2 cycle of the Earth Volcanic gas Dissolution Chemical weathering Sedimentation Degassing! CO 2 dissolves in water and buried in the crust. Abe (2009)! The CO 2 buffer may have stabilized the Earth s climate.

9 Long-term trend of solar luminosity! 2530 Phase diagram of H 2 O Pressure (atm) Ice Mars Earth Liquid Vapor Venus Temperature

10 ! Venus may have had an ocean in early stage of its evolution.! The ocean evaporated and water vapor was lost to space through atmospheric escape. This explains the enrichment of deuterium (D) in the Venus atmosphere relative to the Earth s. Once the ocean disappeared, CO 2 and S-containing species will have been released to the atmosphere. Image provided by ESA! Mars may have had a thick CO 2 atmosphere in early stage of the revolution and have sustained a warm, humid environment via its greenhouse effect.! The loss of CO 2 to space may have caused cooling of the climate. NASA

11 DTS! KST! KST! KST! DTS W!! W! XAT!

12 Origin of sulfur-rich environment! The cloud is related to the sulfur-rich atmosphere of Venus. Atmospheric SO 2 will be oxidized via photochemistry to generate H 2 SO 4, although the chemical path is still unclear.! On Earth, most of the volatile sulfur resides in the ocean as sulfate ions. The sulfuric acid cloud of Venus may also be a consequence of the absence of an ocean.

13 YXXY!!!!

14 ! Outward thermal flux > Incoming solar flux!! Internal heat source The Earth's internal heat flux is 1/40000 of the Incoming solar flux. This heat comes from a combination of residual heat from planetary accretion and heat produced through radioactive decay. Internal heat of gas giants!! Internal heat sources include the rainout of helium-rich droplets and, possibly, continued Kelvin- Helmholtz contraction. The Kelvin Helmholtz mechanism is an astronomical process that occurs when the surface of a star or a planet cools. The cooling causes the pressure to drop and the star or planet shrinks as a result.

$V+*9*0)!3,)<0!H05/,.ZY[[\' "0/;)8-!)6!3*+50/+,.!023*),+4)5 %+?;!10/;)8!;+-!9/-!)B5!$ Spatial coverage Temporal coverage Observable parameters Lander/Rover Limited Limited in

15 V+*9*0)!3,)<0!H05/,.ZY[[\' "0/;)8-!)6!3*+50/+,.!023*),+4)5 %+?;!10/;)8!;+-!9/-!)B5!+8=+5/+:0-!+58!89-+8=+5/+:0-! Spatial coverage Temporal coverage Observable parameters Lander/Rover Limited Limited in many cases Any Orbiter Whole surface Long Relatively limited V,)758]<+-08! )<-0,=+4)5 Q;)*0!-7,6+?0 Repeatedly Limited, but large instruments can be used

16 !! Venus orbiter AKATSUKI Science target : Weather of Venus! Mechanism of super-rotation! Structure of meridional circulation! Meso-scale processes! Formation of clouds! Lightning! Active volcanism, inhomogeneity of surface material Science instruments! 1µm Camera (IR1)! 2µm Camera (IR2)! Longwave IR Camera (LIR)! Ultraviolet Imager (UVI)! Lightning and Airglow Camera (LAC)! Ultra-stable oscillator (USO)! Launch: May 2010 Arrival: Dec 2015 Super-rotation : the most mysterious wind in the solar system Near-IR images taken by Akatsuki The Venus atmosphere is rotating 60 times faster than the solid surface.

Turbulence Thermal tides Cloud Troposphere Hadley

17 Diverse planetary meteorology Mechanism of super-rotation Stratosphere Acceleration Waves or Turbulence Thermal tides Cloud Troposphere Hadley circulation Thermal tides Gravity waves NP Eq SP NP Eq SP NP Eq SP

transport of SO 2, H 2 O H 2 SO 4 condensation circulation of SO 2, H 2 O, CO Equator 20

H 2 O from decomposition of H 2 SO 4 Pole Clouds form through material exchange between the

! 4 cameras sounding different altitudes, a high-speed lightning detector, and an ultra-stable

18 .#','( )#$&*+,%- "#$%&'( )#$&*+,%- Alt. (km) Photochemical production of H 2 SO 4 from SO 2, H 2 O, CO 2 Upward transport of SO 2, H 2 O H 2 SO 4 condensation circulation of SO 2, H 2 O, CO Equator 20 unknown meridional circulation Downward transport H 2 SO 4 evaporation production of SO 2 and H 2 O from decomposition of H 2 SO 4 Pole Clouds form through material exchange between the two different atmospheric regions D T (S^! +0,)-)*- Observation from an orbiter!! 4 cameras sounding different altitudes, a high-speed lightning detector, and an ultra-stable oscillator for radio science!! Constructing 3-D model of atmospheric dynamics PI: S. Watanabe PI: Y. Takahashi PI: M. Taguchi µ PI: N. Iwagami PI: T. Imamura µ PI: T. Satoh

Onboard instruments Instrument FOV Detector Filters Width Targets 1-µm Camera 12 Si-CSD/CCD 1.01 µm (night) 0.04 µm Surface, Clouds IR1 1024 x 1024 pix 0.97 µm (night) 0.04 µm H2O vapor 0.

01 µm Clouds 12 PtSi-CSD/CCD 1.735 µm (night) 0.04 µm Clouds, Particle size 1024 x 1024 pix2.26 µm (night) 0.06 µm 2.32 µm (night) 0.04 µm CO below clouds 2.02 µm (day) 0.04 µm Cloud-top height 1.

19 Onboard instruments Instrument FOV Detector Filters Width Targets 1-µm Camera 12 Si-CSD/CCD 1.01 µm (night) 0.04 µm Surface, Clouds IR x 1024 pix 0.97 µm (night) 0.04 µm H2O vapor 0.90 µm (night) 0.03 µm Surface, Clouds 2-µm Camera IR2 UltraViolet Imager UVI Longwave IR Camera LIR Lightning & Airglow Camera LAC Ultra-stable oscillator for Radio Science RS 0.90 µm (day) 0.01 µm Clouds 12 PtSi-CSD/CCD µm (night) 0.04 µm Clouds, Particle size 1024 x 1024 pix2.26 µm (night) 0.06 µm 2.32 µm (night) 0.04 µm CO below clouds 2.02 µm (day) 0.04 µm Cloud-top height 1.65 µm (cruise) 0.3 µm Zodiacal light 12 Si-CCD 283 nm (day) 15 nm SO2 at cloud top 1024 x 1024 pix 365 nm (day) 15 nm Unknown absorber 12.4X Bolometer 10 µm (day/ 4 µm Cloud-top x 328 pix night) temperature 16 8 x 8 APD nm (night) 4.2 nm OI lightning (50kHz sampling nm (night) 4.7 nm O2 HerzbergII ariglow in lightning nm (night) 3.1 nm OI airglow mode) nm (night) 3.5 nm OI airglow X-band Vertical prifiles of T, (8.4GHz) H2SO4 (g), Ne 3D observations Akatsuki Temperature and H 2 SO 4 vapor profiles (RS) Airglow LAC Sulfur dioxide UVI Cloud temperature LIR Lower clouds IR1, IR2 Wind vectors Carbon monooxide IR2 Lightning LAC Water vapor IR1 90 km 65 km 50 km km Active volcanoes / Minerals IR1 Stratosphere Clouds Troposphere Surface

20 Observation sequence Close-up images Stereo viewing Limb images Continuous mediumresolution images (2 hours interval) Ground station Temperature / H 2 SO 4 vapor / Ionosphere by radio occultation High-resolution images (1-2 hours interval) Lightning/Airglow in umbra

21 Complementary missions Instruments Akatsuki (JAXA) cameras Radio science Venus Express (ESA) spectrometers 1 camera Plasma analyzer Magnetometer Radio science Target Atmospheric dynamics Atmospheric chemistry and dynamics, Surface processes, Plasma environment Orbit Equatorial Polar LAC LIR UVI IR1 IR2

22 20105

23 Failure of Venus orbit insertion!! The Venus orbit insertion (VOI) scheduled for Dec 7, 2010 has failed due to a malfunction of the propulsion system. The check valve between the helium tank and the fuel tank was blocked by an unexpected salt formation during the cruising from the Earth to Venus. As a result the orbital maneuvering engine (OME) became oxidizer-rich and fuelpoor condition, which led to an abnormal combustion in the engine with high temperature, and finally the engine was broken. VOI trial on Dec. 7, 2010 propulsion system Failure of VOI Dec 7, 2010) 560,+46*!'%1*,! _0,9)8!Z!TX`!8+.-! /0%,#!'%1*, Sun 2$34+!'%1*,! _0,9)8!Z!TT\!8+.- [AU]

An orbit control maneuver was conducted using RCS in Nov 2011.

24 Toward the next VOI trial!!! Since OME was destroyed, we decided to use the attitude control thrusters (or reaction control system, RCS) for further orbit maneuver. RCS does not require oxidizer, and we disposed the oxidizer of 65 kg in Oct 2011 to reduce the weight. An orbit control maneuver was conducted using RCS in Nov This operation enables a Venus encounter in Nov The main concern was the high temperature conditions during the perihelion passages. Orbit of Akatsuki during the cruise Expected thermal condition during the cruise b>)3c!/;,7-/0,- bd)e)1c!/;,7-/0,- >;0!/)/+*!3)B0,!)6!^!GK(!/;,7-/0,-!9-!+33,)291+/0*.!TXa!)6!/;0!1+95!/;,7-/0,A!

# Contingency 1:15 Attitude control maneuver +Z panel to the sun Venus 23:20 23:58 Umbra Attitude Control Maneuver VOI-R1c

25 (##$### Sun '#$### Earth Spacecraft &#$### With VOI-R1 maneuver 19:52 UDSC CMD AOS %#$### 4:35 & 4:45 Venus observation 4:15 Attitude control maneuver for Venus observation 3:42 UDSC TLM LOS 3:12 DSN (Cambera) CMD operation "#$### w/o VOI-R1 maneuver # Contingency 1:15 Attitude control maneuver +Z panel to the sun Venus 23:20 23:58 Umbra Attitude Control Maneuver VOI-R1c position 23:51:29 00:12:02 VOI-R1 (1233sec)!"#$###!&#$###!%#$###!"#$### # "#$### %#$### &#$### F*/,+=9)*0/F$J!!!Tf`!51!!!! gxl1

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29 !G+89)!)??7*/+4)5! 10 TXY\]YT]Xf! TXY\]YT]X[! TXY\]YT]YX! TXY\]YT]YY!

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32 &#(#l-!"+,-!#/1)-3;0,0!+58!$)*+4*0! %=)*74)&!H"#$%&'!19--9)5 Arrive at Mars : September 21, 2014 Chassefiere et al. (2007)

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$Diffuse auroras may have additional effects on atmospheric processes. Only a fraction of the de- posited energy results in atmospheric excitation and emission.$

37 Diffuse auroras may have additional effects on atmospheric processes. Only a fraction of the de- posited energy results in atmospheric excitation and emission. Incident particles also ionize and dissociate atmospheric species, as well as heat the target atmosphere. These effects can lead to increased atmospheric escape rates: Ionized par- ticles at sufficient altitudes can escape via out- flow processes, and atmospheric heating can lead to increased thermal escape. _,)?087,0!)6!-3+?0!19--9)5- YA! O9-?7--9)5!+1)5:!/;0!,0*+/08!-?9054-/-! TA! S,:+59P+4)5!)6!/;0!B),L95:!:,)73!95?*7895:!<)/;! -?9054-/-!+58!05:9500,-! `A! O0N595:!/;0!-?905?0!:)+*-! ^A! _*+5595:!/;0!)<-0,=+4)5!10/;)8-!+58!80=0*)3105/!)6! )<-0,=+4)5!/0?;59n70-! \A! "9--9)5!3,)3)-+*! ia! O0=0*)3105/!)6!-3+?0?,+t!+58!)5<)+,8!95-/,7105/-! ga! O0=0*)3105/!)6!:,)758!-.-/01! fa! k+75?;!)6!/;0!-3+?0?,+t!+58!9/-!)30,+4)5! [A! O+/+!+5+*.-9-! YXA!O9-?7--9)5-!+1)5:!/;0!-?905?0!?)11759/.!+58! 37<*9-;95:!3+30,-! 5-10 years

38 Universal understanding planetary environment in multi-parameter space Atmospheric composition, Solar flux, etc. Aerosols, Topography, etc. Rotation rate, Gravity acceleration, Magnetic field, etc. Comparative planetology

Toward Venus orbit insertion of Akatsuki

Toward Venus orbit insertion of Akatsuki Takeshi Imamura (JAXA, Japan) Lightning and Airglow Camera Mid-IR Camera UV Imager Ultra-Stable Oscillator 1µm Camera 2µm Camera Development and launch Objective: