1. The Rosetta Asteroid Targets
M.A. Barucci
LESIA
Observatoire de Paris
Padova, 31/01/2006
M.A. Barucci

2. Rosetta mission: double Asteroid flyby (V= 139 m/s)
2867 Steins --- September 5th, 2008
rel. V = 8.6 km/s
21 Lutetia --- July 10th, 2010
rel. V = 15 km/s

3. Asteroid 21 Lutetia SEMIMAJOR AXIS = 2.435 AU
ECCENTRICITY = 0.164, INCLINATION = 3.064
DIAMETER: 96 km km x 104 x 74 km
(IRAS) (radiometry) (radar data)
It is large enough to allow the mass and bulk density
Evaluation by the radio science experiment
ALBEDO: 0.22± ±
(IRAS) (radar data) (radiometry) (polarimetry)
PREVIOUS TAXONOMICAL CLASSIFICATION:
M (Tholen), M0 (Barucci& Tholen) , W (Rivkin) , Xk (Bus)

5. Asteroid 21 Lutetia Rotational period = 8.17  0.01h
Pole solution: RADAR OBS. (Magri et al, 1999)
prograde rotation, axis ratio: 1.26:1.15:1.0
pole: 1= 228o  11,  1= +13o  5 or
2= 48o  11,  2= +5o  5
Pole solution: LIGHTCURVES ANALYSIS (Torppa et al., 2003)
prograde rotation, axis ratio: 1.4:1.2:1.0
pole: 1= 220o  11,  1= +3o  10 or
2= 39o  10,  2= +3o  10
(Torppa et al., 2003)

6. 21 Lutetia
Spectrum: Moderately red slope ( m), generally flat ( m), possible absorption band at 3 m.
Meteorite analogs: carbonaceous chondrites

7. Birlan et al. 2003
IRTF obs, 30 March 2003: IR featureless spectrum Visible spectra from Busarev (2003) and Lazzarin et al show faint abs. features (440 and 670 nm) possibly due to hydrated silicates. Rivkin et al. (2000) observed the 3 micron band diagnostic of water of hydratation

8. Birlain et al. 2005

9. Birlain et al. 2005

10. Vigarano is CV meteorite:
Chondrules (30%-50%), chondrite fragments,
metal, sulfate grains, and
magnetite and metallic iron (2-3%)
- Low porosity (1-10%)

12. Absorption bands

13. 21 Lutetia
Polarization: The inversion angle is the largest ever observed
for asteroids.
Lutetia has the lower radar albedo measured for any M type class

14. 2867 Steins SEMIMAJOR AXIS: 2.364 AU
ECCENTRICITY = 0.146, INCLINATION: 9.944o
DIAMETER: km
ALBEDO: ? ( )
Period=6.06+/-0.05 hrs
(Hicks & Bauer, 2004) Ld
P= / hrs
(Weissmann et al. 2005)

16. 2867 Steins sharp 0.5 m band faint 0.9 m band
(sulfides, troilite or oldhamite)
faint m band
(iron bearing pyroxene, orthopyr. or forsterite)
Type E
EII type, Angelina like
partial melts derived from enstatite chondrite like parent bodies.
ALBEDO determination needed!!!!
--- EL6 enstatite chondrite Atlanta
.…entatite achondrite (aubrite)
(Barucci et al., 2004)

17. E-type asteroid
E type surface composition seems to be dominated by iron-free or iron-poor silicates as enstatite, forsterite or feldspar, and resembles the aubrite meteorites spectra. They are a small population (around 20 asteroids classifies as E type up to now) located mainly in the inner main belt)
-0.5 micron band (Burbine et al, 1999; Fornasier & Lazzarin, 2001):this band is very peculiar and its origin not yet fully understood. It might be due to sulfides such as oldhamite or troilite (sulfides are known constituent of the aubrite meteorites)
-0.9 and 1.8 micron bands: due to iron bearing pyroxene such as orthopyroxene or forsterite (Clark et al., 2004)

18. Waiting for 2008……. New Observations: VLT SPITZER
To determine the albedo +
To determine the rotational axis
and the best shape model

19. Thermal observations of Steins and Lutetia at ESO
Steins - VISIR at UT3
Lutetia - TIMMI2 at La Silla 3.6m
N band
spectrum
mm, R=160

20. Lutetia: 2m Faulkes 2005-12-11 (3.5 h)? 2005-12-14 (2 h)?
Spitzer Space Telescope (IR Spectra + Photometry):
Steins
Lutetia
Light curves
Steins: ESO NTT (4 h)
(2 h)
Lutetia: 2m Faulkes (3.5 h)?
(2 h)?

21. Asteroid fly-by What we need: - Maximum coverage of the surface
- Observations at 0 phase angle
To be in agreement with the Radio science for Lutetia
to determine the mass and the density

22. Fly-by geometry for Lutetia
  The sun vector,  , is in the fly-by plane. The angles , , ,  are as follows:  = 18.9°;  = 3.7°;  = 9.6°;  = 0.5°

23. Nominal fly-by geometry for Steins
The sun vector  is in the fly-by plane. The angles , , ,  are as
follows:  = 23.8°;  = 5.9°;  = 50.2°;  = 0.5°

24. Birlain et al. 2005

25. Physical characterisation of igneous asteroids (E-M-X type)
E type surface composition seems to be dominated by iron-free or iron-poor silicates as enstatite, forsterite or feldspar, and resembles the aubrite meteorites spectra. They are a small population (around 20 asteroids classifies as E type up to now) located mainly in the inner main belt
M type are probably composed of metals such as iron and nickel and presumed to be the progenitors both of differentiated meteorites such as iron meteorites and of undifferentiated meteorites like the enstatite chondrites
From 1995 some absorption bands have been identified on E and M type asteroids:
- 3 micron band (Rivkin et al 1995, 2000): surprising as typically due to the first overtone of H2O and to OH vibrational fundamentals on hydrated silicates
if really due to hydrated silicates, E and M type object
might not be all anhydrous and igneous as previously believed and the thermal scenario in the inner main belt might be revised.

26. Priorities for Double Asteroid Mission
SWT 15th (12/2003)
Rhodia Lutetia 159 m/s
Luichewoo Lutetia 129 m/s
Steins Lutetia 139 m/s
Baetsle Izvekov m/s
Baetsle Fogelin m/s
Luichewoo Izvekov m/s
Rhodia Izvekov 112 m/s
Rodhia Fogelin 113 m/s
Steins Izvekov m/s
Sofala Izvekov 146 m/s
Steins Fogelin m/s
Luichewoo Fogelin m/s

27. Barucci et al. 2004

28. Barucci et al. 2004

29. Mission to 67P/Churyumov-Gerasimenko
Launch: 2004/03/2
Earth /03
Mars /03
Earth2 2007/11
Steins 2008/09
Earth /11
Lutetia 2010/06
Comet /05
RDV /08
(4 UA)

30. Hayabusa mission: -Itokawa
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