Venus : the lost world Pierre Drossart LESIA, Observatoire de Paris

10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System Venus (1956 version) 2

10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System Venus, 2011 version

10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System A brief history of Venus space exploration 50 years of exploration by Russian and American spacecraft and more recently Europe Mariner, Venera, Pioneer, Vega, Magellan and flybys by Galileo, Cassini Venus Express Firsts: Mariner2, Venera7, Pioneer, Vega, Venera 15 4

Pioneer Venus (NASA) septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System 5 Orbiter and multiprobe mission – Characterizati on of the atmosphere

10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System Landscapes on Venus ( Venera 13 et 14) 6

10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System Galileo (1990) : ultraviolet and infrared images 7

10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System The surface of Venus as seen from Magellan (1992) 8

10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System Venus Express : a small ESA mission A small scale mission with well defined objectives, fast (three years of development!) Launch : 9 November 2005 Orbit insertion: 11 April 2006 Today ! 2344 orbits 9

10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System Venus Express 11

10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System Some Venus Express outstanding questions Is there an active volcanism on Venus today ? What is the pace of atmospheric escape Where Venus « earth-like » at the beginning and how long ? When took place the runaway greenhouse event ? Is there plate tectonics on Venus (past, present ?) Did Venus had a magnetic field ? 12

10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System Venus Express measurements : Atmosphere and surface of Venus Ionosphere Magnetic field Atmospheric measurements Atmospheric drag measurements Futur e (=> 2014 ?) aerobraking Measurements in solar maximum period 13

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10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System 15 VIRTIS for Venus Express P. Drossart, G. Piccioni – in mem. A. Coradini

10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System Atmospheric composition Spectroscopic measurements give accurate measurements of the planetary atmospheres 16

The infrared spectrum of Martian atmosphere Solar reflectedThermal CO 2 H 2 O CO 2 COCO 2 ISO-SWS Lellouch et al., 2000 Hydrated silicates Reflected sunlight -> mineralogy Thermal emission -> T(z), winds 10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System 17

10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System Venus nightside windows 2.3  m CFHT/FTS observations (Res = 0.15 cm -1 ) [Taylor et al. 1997] Altitude range: km Absorbers: CO 2, H 2 O, HDO, CO, OCS, SO 2, HF 18

Venus night side spectra Venus Express / VIRTIS Obs. 10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System 19

10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System The surface of Venus Venus Express detects thermal emission from the surface of Venus through narrow atmospheric windows (0.9, 1.01, 1.10, 1.18µm) 20

10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System Surface temperature map of Venus (South polar view) VIRTIS/Venus Express Magellan (radar) 21

10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System VIRTIS derived altimetry Magellan altimetry Variation of the rotation period of Venus between Magellan and Venus Express A revised period of rotation of Venus of ± days is significantly different from the value of ± recommended by IAU Mueller et al. 22

10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System Idunn Mons Lat -46° Long 214.5° Thermal radiation Radar image VIRTIS image Recent lava flows(< 250 MA) Smrekar et al., Science Emissivity anomalies

10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System Clouds of Venus Venus Express gives access to short and medium term evolution of Venus meteorology 24

10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System Clouds of Venus UV variability 25

10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System Cloud altitude Measurement of upper cloud altitude from CO 2 infrared absorption (VIRTIS) 26

Detailed example of some results: Wind Maps orbit 475 (upper cloud 5.10µm) 80°S 70°S 60°S 6 image pairs separated by one hour

Variable Morphology of the South Polar Vortex Images taken by VIRTIS-M InfraRed channel showing the upper cloud (~65km). These are some examples of the highly variable morphology, from Orbit Insertion to orbit 921. The traditional “dipole” structure of the vortex (Piccioni et al., 2007) was characteristic for the first days of the Venus Express mission, but later begun to show many different structures. Even if the vortex is observed to vary slowly over the long imaging sequences obtained in an orbit (typically 2 to 6 hours), the morphology may change completely in timescales ~ 24hours.

10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System Meteorology of Venus Short and mid term Venus meteorology has been studied from Venus Express 29

10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System Zonal and meridional wind profiles : 380 nm (blue), 1.74 µm (red) Sánchez-Lavega et al. (GRL, 2008): 980 nm data (violet) 30

10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System Aeronomy of Venus Upper atmosphere of planets exhibit very rich physical proccesses, essential to understand the interaction of the planet with its environment 31

OH and O 2 emission on Venus 10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System 32 A.V. Shakun, PhD Thesis 2012

10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System Oxygen distribution Piccioni et al., JGR 2009 Soret et al., Icarus 2010 The Oxygen distribution is pretty correlated with the nightglow intensity (dynamics driven) R. Hueso et al. 33

Lopez-Valverde, Gilli,… PSS, 2011 Results from CO  m analysis Altitude variations Similar behaviour in the three planets Variation of the shape of the emission Maximum of the emission at 50 km, 110 km, 100 km on Earth, Venus and Mars. - SH bands - pressure level 1000 times denser on the Earth Pierre Drossart The Golden Age of the Solar System 10 septembre 2012 Rome 34 Gabriella Gilli, IAA, PhD Thesis 2012

VIRTIS observations for CO 2 non-LTE 10 septembre 2012 Rome Pierre Drossart The Golden Age of the Solar System 35 Gilli et al, JGR 2009

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Venus as seen by Akatsuki on 6 December 2010 from km (UV- 380 nm) Venus : quid nunc ?