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Ro etta at teins and toward utetia

Ro etta at teins and toward utetia. S. L. Marcello Fulchignoni Venezia, April 1 st , 2009. 1986. 1987. 1989. 1991. 1988. Rosetta. A Comet rendezvous Mission. Scientific Payload. Rosetta. 11 Orbiter Instruments/ (Instrument Packages) 18 Experiments.

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Ro etta at teins and toward utetia

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  1. Ro etta at teins and toward utetia S L Marcello Fulchignoni Venezia, April 1st , 2009

  2. 1986 1987 1989 1991 1988

  3. Rosetta A Comet rendezvous Mission

  4. Scientific Payload Rosetta • 11 Orbiter Instruments/ • (Instrument Packages) • 18 Experiments Payload Mass: ~170 kg + Lander: ~110 kg 10 Lander Instruments/ (Instrument Packages) => 16 Experiments Payload Mass: ~27 kg

  5. Rosetta was also seen from the Earth

  6. B S 1993 1996 2530 Shipka 3840 Mimistrobel S C 2703 Rodari S 1998 4979 Otawara 140 Siwa

  7. 2004 C 21 Lutetia E 2867 Steins

  8. 2867 Steins SEMIMAJOR AXIS: 2.364 AU ECCENTRICITY = 0.146 INCLINATION: 9.944o Period=6.06+/-0.05 hrs Ld (Hicks & Bauer, 2004) P=6.048 +/-0.007 hrs (Weissmann et al. 2005)

  9. SHAPE & POLE OF STEINS Lamy et al., 2008 Shape: Pole coordinates: a=5.73 km b=4.95 km c=4.58 km λ1 = 250° ± 5° β1 = - 89° ± 5°

  10. α = 33° Light Curve and Modelled Shape OSIRIS Observations Distance to Steins 12 Mio. km on 20. Aug. 2008 Shape model of Steins

  11. 2867 Steins sharp 0.5 m band (sulfides, troilite or oldhamite) faint 0.9 m band (iron bearing pyroxene, orthopyr. or forsterite) Type E EII type, Angelina like partial melts derived from enstatite chondrite like parent bodies. --- EL6 enstatite chondrite Atlanta .…entatite achondrite (aubrite) (Barucci et al. 2005)

  12. 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 (25 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)

  13. Polarimetric results on 2867 Steins Tx slope inv Steins 0.037 17.3 E 0.04 17.8 S 0.09 20.1 M 0.09 23.5 C 0.28 20.5 (Fornasier et al., 2006) Polarimetric properties are consistent with high albedo E-type asteroids Albedo = 0.450.1

  14. SPITZER DATA OF 2867 STEINS Lamy et al. (2008) A=0.34 ± 0.06

  15. SPITZER DATA OF2867 STEINS (PI P. Lamy) 6 hours of full coverage on 22 November 2005, with IRS, for a total of 14 spectra [5-38 micron]. Observing conditions: DSpitzer = 1.60A Phase =27.2° DSun= 2.130 AU Emissivity spectra were obtained dividing the Spitzer spectra by the SED (calculated using the thermal model presented Lamy et al., 2008) (Barucci et al., 2008)

  16. SPITZER DATA OF 2867 STEINS Steins emissivity spectrum is very similar to that of the aubrite meteorites (enstatite achondrites, which have the E-type asteroids as parent bodies) and of the enstatite mineral (Barucci et al., 2008)

  17. Enstatite chondrites

  18. Steins Fly-by Overview • 4 August 2008 to 3 October 2008 • Closest approach: • 5 Sept. 2008 18:58 • rH = 2.14 AU, Δ = 2.41 AU • Relative velocity: 8.62 km/s • Targeted minimum flyby distance: 800 km

  19. Final fly-by scenario: a complex matter • S/C flip started 40 min before closest approach • 20 minutes duration • Phase angle coverage: 0-140° • Phase angle at approach: 38.5 deg • Phase angle zero at 1280 km

  20. NAC best res. Image (100m/px) 5Sept UT: 18:28, dist:5200 km, phase=30° WAC res. 100 m/px 5Sept UT: 18:36:45, dist=1029 km,phase=12° WAC best res. Image (80m/px) 5Sept UT: 18:38:15 dist:806km,phase=50 °

  21. Colour images

  22. Steins Albedo: 0.38 ± 0.05

  23. WAC Spectrophotometry 24

  24. Virtis H Steins • Spectrum in radiance units (still relative – absolute calibration waiting for filling factor accurateestimatesfrom final pointing)

  25. VIRTIS-M 288 spectral bands ( 0.25-5 micron) spatial resolution is ~ 300 m/pix

  26. Temperature (left)and emissivity( right) Maps for ε =1 230 200

  27. Signal mm  FroidChaud  Signal continuum détecté par MIRO peu après l'approche maximale à Steins le 5.78 Septembre 2008 Temps après l'approche maxi -> Signal submm  FroidChaud 

  28. Asteroid 21 Lutetia • SEMIMAJOR AXIS = 2.435 AU • ECCENTRICITY = 0.164, INCLINATION = 3.064 • DIAMETER: 96 km109 km 130 x 104 x 74 km • (IRAS) (radiometry) (radar data) • It is large enough to allow the mass and bulk density determination • by the radio science experiment • ALBEDO: 0.22±0.020.17±0.07 0.110.09 • (IRAS) (radar data) (radiometry) (polarimetry) • D= 98.3 ± 5.9 km A=0.208 ± 0.025 (Mueller et al. 2006) • PREVIOUS TAXONOMICAL CLASSIFICATION: • M (Tholen), M0 (Barucci & Tholen) , W (Rivkin) , Xk (Bus)

  29. Asteroid comparative sizes 21 Lutetia 2867 Steins

  30. 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 Shape and pole solution: LIGHTCURVES ANALYSIS (Torppaet 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

  31. 21 Lutetia • Spectrum: Moderately red slope (0.3-0.75 m), generally flat (0.75-2.5 m), possible absorption band at 3 m. • Meteorite analogs: carbonaceous chondrites

  32. Aqueous altered materials ? ferric iron spin-forbidden absorption phyllosilicates (jarosite…) oxidised iron Lazzarin et al. 2004

  33. Birlan et al. 2006 andRivkin et al. (2000) observed the 3 micron band diagnostic of water of hydratation

  34. 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

  35. 21 LUTETIA SPITZER DATA 8 hours of full coverage on 10 December 2005 with IRS, for a total of 14 spectra [5-38 micron].

  36. 21 Lutetia the STM applied to Spitzer data gives albedo = 0.18 beam. factor=1.49 Also Mueller et al. (2006) with ground based thermal observations determined a similar albedo value A=0.208 ± 0.025 D= 98.3 ± 5.9 km

  37. 21 LUTETIA • The Lutetia emissivity spectrum is completely different from that of the iron meteorites, so the possible metallic nature for Lutetia is rejected! • Lutetia is similar to CV3 and CO3 carbonaceous chondrites, meteorites which experienced some aqueous alteration

  38. THE END RdV : 21 Lutetia 10 July 2010

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