Prsentation PowerPoint

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Titan à la lumière de la mission Cassini-Huygens
Athéna Coustenis Athena.coustenis_at_obspm.fr
Laboratoire dEtudes Spatiales et
dInstrumentation en Astrophysique
Observatoire de Paris-Meudon, France
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Titan, un satellite exceptionnel

• Satellite découvert le 25 mars 1655 par Huygens
• Paramètres physiques
• - R 2 575 km
• - m 1,831 MLune
• Paramètres orbitaux
• - a 1 221 830 km 20 RSaturne
• - P 15,95 j
• - e 0,0292

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Ce quon apprit par Voyager 1 - N2 est le
constituent majoritaire - CH4 autres
hydrocarbures - H2 - nitriles - Peu doxygène
H2O, CO, CO2
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Titan et la Terre
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Titan vs la Terre
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Titan la basse atmosphère et la surface restent
largement inconnues
Le problème du méthane où est le réservoir?
Le mystère de la surface quelle est sa
composition?
Océan global dhydrocarbures impossible car
démenti par -échos radar -effets de
marrées -spectres et images
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Images de Titan par le HST
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Quest-ce quon voit sur Titan ???
1.28 µm par VLT/NACO
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La mission Cassini-Huygens
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La mission Cassini-Huygens
Fonctions  Humaines  de Cassini-Huygens
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Huygens et Cassini Hommes et machines
Christiaan Huygens (1629-1695) astronome amateur
Hollandais, découvrit les anneaux de Saturne et,
en 1655, sa plus grosse lune, Titan.
Giovanni Domenico Cassini (1625-1712), astronome
franco-italien, découvrit plusieurs satellites
kroniens Japet, Rhéa, Téthys et Dione. En 1675,
il découvre la Division Cassini le vide entre
deux anneaux majeurs de Saturne.  
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Cassini observe Saturne 21 mars 1684,
Observatoire de Paris
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Trajectoire
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Le parcours
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Le passage à travers les anneaux et linsertion
en orbite autour de Saturne
30 Juin / 1 Juillet 2004
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Les anneaux en ultra-violet
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Japet
Porco et al. 2005
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Encelade et les jets deau
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Encelade et son atmosphère deau
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Encelade

• Quelle est lorigine des panaches?

• Des éjections de vapeur deau très loin du Soleil
  (implications pour les zones dhabitabilité)
• Signes de présence de chimie organique

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Espace vs sol en 2004-2005
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SOURCES OF ORGANIC REACTANTS IN TITAN S
ATMOSPHERE

• Gases that are already present in the atmosphere
  N2, CH4, H2
• Pristine material deposited in the atmosphere by
  comets and interplanetary dust H2O, CH4, CO2,
  (NH3 ?),
• Products of chemical processing of the
  atmosphere
• Photolysis of CH4 N2 ? C2H6, other
  hydrocarbons, polymers, HCN Irradiation by
  energetic particles ? HCN, C2H2, hydrocarbons,
  nitriles
• Plasma initiated chemistry (associated with
  lightning, cometary impacts) ? HCN, C2H2,
  hydrocarbons, nitriles, , aerosols

Cassini/INMS on Titan Waite et al
Thus, a wide variety of simple and necessary
organic species is available along with aerosols
for continued chemistry in Titans atmosphere.
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Chimie organique sur Titan
Wilson and Atreya, JGR 2004
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Des questions encore

• Doù provient latmosphère de Titan?
• - Azote ?
• - méthane ?

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N2 origin
NH3 primordial
N2 by
N2 primordial
thermal dissoc.
shock
photolysis
trapped in planetesimals
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nitrogen formation

• delivered as N2 trapped in ice - no
• very small 36Ar, and no Xe, Kr detected
• by impact dissociation of NH3 (McKay et al, 1988)
  - unlikely
• unrealistic hydrocarbons (15 km haze) and H2 (4
  bar)
• H2O short-circuits path to N2, but not included
• photochemically, from NH3 (Atreya et al, 1978)
• nitrogen arrived primarily as NH3 trapped in ice

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isotopes

• 12C/13CTitan 12C/13CEarth

• 14N/15NTitanltlt 14N/15NEarth

methane replenishment
nitrogen escape
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V1/IRIS
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C2H2
HCN
C3H8
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C2H6
C2H4
Coustenis et al., 2007c
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Titan
The enhancement at the North pole is currently a
factor of 1.5-2 smaller than at the time of the
Voyager encounter for all molecules
Cassini CIRS (2004-5) Coustenis et al.
(2007) (N. winter)
Volume mixing ratio
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Titan et les belles images de Cassini
ISS
Cassini/ISS 26 Octobre 2004 Image de Titan en
fausses couleurs Lat15S long156W
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VIMS
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VIMS
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Titan images Cassini avec VIMS
VIMS
Lescargot Un cryovolcan?
Coustenis Athéna Titan et
la mission Cassini-Huygens
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Titan images Cassini avec VIMS
VIMS
Coustenis Athéna Titan et
la mission Cassini-Huygens
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Titan et les belles images de Cassini (suite)
RADAR
Cassini/Radar Image montrant une géographie
coulée et très Contrastée 1ère indication dune
possible ligne côtière au bord dun lac
Coustenis Athéna Titan et
la mission Cassini-Huygens
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Cassini/RADAR/Titan
Les cratères par le RADAR de Cassini
Terre
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Cassini/RADAR/Titan
Les dunes par le RADAR de Cassini
Terre/Namibie
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Cassini/RADAR/Titan
Des rivières et des lacs au pôle Nord le
réservoir liquide manquant?
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Les lacs sur Titan
Cassini radar
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La sonde Huygens
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3eme orbite autour de Saturne mission Huygens
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319 kg
2.7 m
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Cassini-Huygens la sonde
HASI DWE DISR GCMS ACP SSP
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• Huygens la descente et latterrissage

110-0 km 3ème Parachute (2h13min)
156 km 1er Parachute (2 sec)
155-110 km 2ème Parachute (15 min)
Données transmises via Cassini 2h28min de
descente et 1h12min à la surface Signal via des
radio-téléscopes 5h42min, y compris 3h14min sur
la surface
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Radio detection of Huygens
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Mesures des vents
Essentiellement vers lEst (prograde) Première
confirmation in situ de la superrotation de Titan
- turbulence considérable au-dessus des 120 km -
Vents très faibles entre 60 et 100 km
inexpliqué - Près de la surface des vents très
faibles (1 mètre par second)
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Composition chimique
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La structure thermique

• Dans la haute atmosphere densité temperature
  plus grandes que celles attendues.. Le profil
  thermique présente des ondulations gt
  latmosphere est stratifiée et varie dans le
  temps.Stratopause -86 C à 250 km
• Basse stratosphère tropopause très bon accord
  avec les mesures de Voyager 1.Tropopause -203
  C at 44 km
• A la surface Température -180C
• Pression 1.5 atm

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Mosaïque panoramique en haute altitude (48 à 20
km) Construite à partir dimages DISR MRI et HRI
projetées depuis 34 km. Le Nord est en haut.
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Vue panoramique depuis des altitudes moyennes (17
à 8 km).
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A basse altitude (7 à 0.5 km) La crête
inférieure est entrecoupée dune douzaine de
canaux plus sombres.
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Les hautes terres brillantes deux types de
systèmes fluviaux
Mosaïque panoramique projetée depuis 6.5 km
daltitude montrant les hauts terrains et
linterface brillant-sombre
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Linstrument DISR la caméra-spectromètre de
Huygens
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Température - 180 C Pression 1467 mbar
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Après latterrissage de Huygens sur la surface de
Titan combinaison des images
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Des  cailloux  sur Titan
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Spectre DLIS à 20 m

• - Méthane environ 5 à la surface
• - Surface
• matériau sombre sable imprégnée de CH4
• absorption probable par la glace deau les
  cailloux

CH4
CH4
CH4
CH4
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Surface Observations with the GCMS (Niemann et
al., Nature, 438, 779-784, 2005)

• Detection of various organic compounds on the
  surface
• Ethane, acetylene, cyanogen, benzene and in
  addition carbon dioxide.

Methane evaporated from the surface after warming
from the heated sample inlet as observed by an
increase of the methane signal after impact. A
moist area with liquid methane in the near
sub-surface is indicated.
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Cassini radar
Lat. 80N, 35W. 140 km across. Resolution 500m.
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Why is methane important?

• Role of methane in Titans atmosphere
• provides warming, due to
• hydrocarbon haze in stratosphere (100 K), and
• H2-N2 and CH4-N2 opacity in troposphere (20 K)
  
• (warming) critical to sustain the very
  atmosphere
• of nitrogen,
• no CH4 ? little N2 (condensation)
• Fate of methane
• destroyed irreversibly by photochemistry in
• 10-30 million years
• How to replenish methane?
• meteorology ? no
• biology ? no

Cryovolcanism/outgassing
Grasset et al.
Outgassing from the interior - trapped in CH4
clathrates - hydrogeochemically
(serpentinization) ? ?!
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Methane Origin

• 1. methanogens - no 13C deficiency not seen
• Earth
• biogenic 12C/13C 92- 96 (organic)
• inorganic 12C/13C 89.4 (V-PDB inorganic std.)
  (similar to Saturn, Jupiter, Sun)
• Titan 12C/13C 82.3?1
• 2. arrived as clathrate - possible
• but no Xe, Kr, and very low 36Ar detected
• 3. produced on Titan ? hydrothermal source -
  possible
• but temperature/pressure problem

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serpentinization cartoon
serpentinization
hydration of ultramafic silicates
(olivine/pyroxene) produces serpentine
(Mg,Fe)3Si2O5(OH)4, and methane
Si
H2O
Fe
Mg
serpentine
CH4
H2
C, CO, CO2
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Hydrothermal vents Black Smoker
Juan De Fuca Ridge depth 2222 m exit temp
342 C chimney ht. 10 m
Mid-Atlantic Ridge
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Image prise par la caméra HRI à 3 km daltitude
indiquant, dans la plaine sombre sur laquelle
Huygens va atterrir, un écoulement de fluide
autour dîles plus claires.
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Titan comme si vous y étiez
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Titan des images de la surface avec VIMS et
différentes observations
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La mission Cassini continue
jusquen 2010
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Comment notre vision de Titan a changé lors des
25 dernières années
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Janvier 2025 (?)une mission Post-Cassini
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Athéna Coustenis Laboratoire dEtudes Spatiales
et dInstrumentation en Astrophysique (LESIA)
Observatoire de Paris-Meudon, France Et le
TANDEM Consortium
(155 membres de 11 pays Européens, Et les US,
Canada, Japon, Chine, Taiwan)
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Pourquoi Titan et Encelade après Cassini-Huygens?
Les révélations de Cassini-Huygens (2004-2010)

• Even when the extended mission is taken into
  account, Cassini-Huygens will have provided us
  with
• a few Enceladus flybys
• about 60 hours of Titan flybys closer than
  10,000 km
• 35 of high-resolution RADAR/SAR coverage (1-2
  km) of Titan and only a few of near-IR surface
  mapping at 2-km resolution
• 14 Titan radio-occultations and a few hundred
  hours of far/mid IR observations
• 70 Titan magnetic field observations 50
  ionospheric profiles

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Why a new mission?

• Cassini-Huygens did a great job in revealing the
  basic natures of Titan and Enceladus as
  geologically active planetary objects with
  atmospheres and of high astrobiological interest.
• But it raised many fundamental questions and
  opened the path for a mandatory exploration that
  will give us the answers.

• How? With TANDEM !
• with a Titan-dedicated orbiter for complete
  mapping of the surface and exploration of as yet
  unknown parts of the atmosphere
• with a full multi-site in situ exploration of
  Titan with balloon and probes
• with extensive in situ exploration of
  Enceladus
• with a host of new instruments adapted to this
  kind of exploration
• at a later season so as to study Titan in the
  2026-2031 timeframe, at a season complementary to
  that observed by Cassini
• A long-lived multi-element architecture enables
  powerful synergistic science via simultaneous
  measurements at different places or scales. We
  will thus be able to address questions that have
  not been in Cassini-Huygens' objectives surface,
  interior, astrobiology, organic content, etc

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TANDEM A combined Post-Cassini-Huygens
exploration of Titan Enceladus. In situ study
of Titan as a system Enceladus as a
system Origins, evolution and interiors
Astrobiological potentials
ESA Cosmic Vision 2015-2025 Call Themes
addressed 1.3 Life and habitability in the
Solar System and 2.2 The giant planets and
their environments, but also 2.1 From the Sun
to the edge of the Solar System
http//www.lesia.obspm.fr/cosmicvision/tandem/
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Science objectives

• Titan as a system
• Upper atmosphere/magnetosphere
• Neutral atmosphere
• Surface
• Enceladus as a system
• source of plumes and jets
  
• Titan Enceladus
• Surface/interior/origin and evolution
• Astrobiology
  

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Titan Upper Atmosphere/Induced Magnetosphere

• Agnostosphere (400-950 km) not reached by most
  measurements
• Important region for complex organic
  ion-molecule aerosol synthesis with relevance
  for the entire atmosphere and astrobiology
  Cassini-Huygens not equipped to study much of
  Agnostosphere/ Thermosphere/Ionosphere chemistry
• Lower boundary of induced magnetosphere
  Internal magnetic field present on Titan?
• Combination of in-situ/remote observations with
  dedicated orbiter!

• Large gaps in SLT, LAT ALT coverage and
  temporal coverage of upper atmosphere/induced
  magnetosphere
  
• Magnetotail/plasma wake region at intermediate
  distances (gt 4 RT) important for mass budget -
  Influence on dynamics of Saturnian magnetosphere
• Temporal variations due to external solar and
  magnetospheric conditions
• Improved and new instrumental payload
  configuration necessary to answer new questions
  raised during Cassini-Huygens mission
• Advanced INMS to measure the very heavy neutrals
  and positive/ negative ions
• DC electric field (plasma speed) for studying
  electrodynamic coupling
• Millimetre Sub-mm spectrometer for neutral wind
  
• A spinning orbiter (part-time at least) essential
  for E-field and particle pitch angle distribution
  measurements at necessary time resolution

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Titans neutral atmosphere Motto Understand the
workings of Titans atmosphere!

• ? Atmospheric structure
• Determine the near-surface temperature and
  temperature profile in the polar troposphere
• ?Atmospheric dynamics
• Search for evidence of atmospheric tides and
  waves
• Map out the meridional circulation and its change
  with seasons
• Seek evidence of orographic and convective winds
  and clouds
• ? Atmospheric composition and chemistry
• Hydrocarbons, nitriles, polymerisation

• ? Climate and alkanological cycle
• Characterise the structure and evolution of the
  polar vortex
• Map the seasonal and latitudinal variation in the
  tropospheric methane abundance
• Determine the physical and chemical properties of
  clouds
• Search for evidence of methane outgassing and
  evaporation from lakes
• ? Quantify the coupling of the surface and
  atmosphere in terms of mass and energy balance

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Titans surface
Understand Titans Geological System What are
the processes of liquid cycles and recharging
mechanisms and their relation to cryo-volcanism,
tectonics and erosion? -gt need to obtain infrared
stereo and radar mapping with resolutions lt100 m
-gt need highest-resolutions for specific sites
(lt 1 m) -gt need global compositional mapping
with resolutions lt 1 km -gt need sounding radar
to determine the depth and vertical structure of
surface and subsurface deposits and methanofers
Understand Titans liquids Are the lakes and
seas filled with methane and ethane, and do they
extend to a subcrustal hydrocarbon methanofer
system over a larger area of Titan? Where is
all the ethane? Are these processes affected by a
deep-water ocean, e.g. through fissures by tidal
flexing? -gt need to obtain infrared stereo and
radar mapping with resolutions lt100 m -gt need
highest-resolutions for specific sites (lt 1 m)
-gt need global compositional mapping with
resolutions lt 1 km -gt need sounding radar to
determine the depth and vertical structure of
surface and subsurface deposits and
methanofers -gt need measures of the gravity field
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• Understand Titans surface composition
• What is the composition of surface and subsurface
  material?
• What are the nature of chemical alteration
  processes
• -gt need in-situ mineralogical/chemical
  analyses
• -gt need compositional context and infrared
  imaging from a near-surface platform
• (also required for selecting sampling sites
  for surface chemistry)
• -gt need global compositional mapping with
  resolutions lt 1 km

Titans surface contd

• Understand Titans atmosphere/surface interaction
• What are the seasonal- and longer-scale
  dependencies of the distribution of materials
  across the surface?
• What is the long term history of dunes?
• -gt need multiple coverage of infrared stereo and
  radar mapping and highest-resolutions mapping of
  specific sites (lt 1 m)

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Enceladus as a system

• Origin, nature and properties of the jets and
  plume
• (including dynamic properties, temporal
  variability, spatial distribution of gas/dust)

• Existence, depth and extent of sub-surface liquid
  water (implications for heat sources, e.g. tidal
  heating, and composition, including possibly
  clathrates)
• Signs of past/present life (including organic
  inventory)

• Other Objectives include
• Characterize the surface and its heterogeneity
  (including resurfacing and tectonic processes,
  vent structure, impact craters)
• Characterize the interior (including structure
  and mass distribution, gravity field, global
  topography, endogenic and exogenic dynamics)
• The impact of Enceladus on the magnetosphere
  (including magnetospheric processes, plasma
  loading effects)
• Influence of Enceladus on other satellites
  (including surface contamination)
• Influence of Enceladus on ring structure
• Determination of dust flux into system

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Titan and Enceladus interior early evolution
Science Goals

• Present interior structure
• Structure, heterogeneities in radial mass
  distribution.
• Tidal Heating.
• Geochemical constraints on bulk composition and
  internal differentiation.
• Presence and extent of liquid water.
• Tidally induced deformation, magnetic field and
  seismicity
• Depth to liquid water reservoirs, radial extent
  and electrical conductivity.
• Lateral variations in thickness and rigidity of
  the overlying icy crust.
• Heat sources, cryovolcanism and eruptive
  processes
• Intrinsic heatflow, near-surface thermal
  gradient.
• Delivery of nitrogen and methane to the surface.
• Geochemical and geophysical constraints on bulk
  composition and internal differentiation
• Interior-surface interactions
• Size and state of the rocky core, structure of
  the crust and depth of the methanifer, sources
  of atmospheric methane
• What is the crustal history?
• Early Evolution
• Noble gas isotopic ratios (Ar, Kr, Xe, Ne) of
  surface materials and aerosol depositions,
  14N/15N isotopic ratios, presence of H2, N2 or CO
  at mass 28, presence of NH3, gas/dust ratio of
  plumes.
• We need
• to derermine topography, gravity and
  magnetosphere

Titans internal structure
Possible internal structure for Enceladus
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Astrobiology Titan
Similarities of Titan with the Earth

• Atmosphere, structure, composition, greenhouse
  properties, climate similarities (haze ? ozone)
• Many geological similarities (liquid bodies,
  fluvial networks, dunes, (cryo)-volcanism,
  mountains, tectonics, erosion, impact craters )
• Ice on Titan ? rock on Earth
• Methane cycle ? water cycle
• BUT Still to be fully understood!!

In addition an organic chemistry with many
similarities with the early Earths prebiotic
chemistry
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Scénario de mission

• Vaisseau 1 Orbiteur pour Encelade/Titan, et des
  pénétrateurs sur Encelade
• Lancement autour de 2018, arrivée à Saturne,
  puis survols de Titan et Encelade
• Largage des pénétrateurs sur Encelade
• Le vaisseau se positionne autour de Titan
  uniquement

• Vaisseau 2 Titan
• Ballon, sondes
• Arrivée à Titan après lorbiteur.
• Déploiement du Ballon et des sondes

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Possible architecture de mission
Une option possible consiste en ? Un orbiteur
(TitanEncelade) ? Un Ballon/Montgolfière dans
Titan et des mini-sondes ? Pénétrateurs/
atterrisseurs pour Encelade
Lorbiteur servira aussi de relais
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Une Montgolfière sur Titan
Extract from Scientific American , Oct. 2007
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Strawman Payload possibilities

• The strawman instrument payload proposed for
  TANDEM provides a strong set of cross-cutting
  complementary observational capabilities, as
  determined by our traceability matrix
• On the orbiter Multispectral spectrometers,
  Cameras, gradiometer, magnetometers, sub-surface
  radar, radio science, etc
• On the balloon GCMS, cameras, GPR, HASI, etc
• On the mini-probes with surface packages GCMS,
  radio, seismometers, organic matter and surface
  composition analyzers, GPR, microscope
• and generally a host of new conceptual
  instruments will scan all spectral ranges and
  return data of high level of detail and quality.
• The combination of orbiter and in-situ elements
  provides opportunities for both large and small
  payloads, engaging a potentially wider community
  of instrument providers from a variety of member
  states.
• The heritage of previously successful missions
  such as Cassini-Huygens and new ones currently
  under study (such as ExoMars, etc) will be
  extremely beneficial to the definition of the
  technological feasibility and maturity of the
  proposed concept.

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Key technology study areas

• Improve upon Huygens EDL technology
• Extend to controlled dips for aerocapture
• Technology development for balloons, mini-probes
  penetrators
• DtE communications
• RTG heat exchanger, material development (2-layer
  concept) and drop deployment test for
  Montgolfière balloon. Small RTGs enable many new
  options (small balloons, long-lived seismic
  stations etc)
• Microelectronics development which can be done
  under low radiation specification for mission.
• Develop tether system and surface sampling
  capabilities.
• Trade studies on solar electric propulsion
• Trajectory designs for probe/landers/ penetrators
  releases on Titan and Enceladus
• On-board science autonomy data selection,
  compression and storage
• CDH and Telecom systems

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Le futur Post-Cassini