Is there a magnetic field on asteroid (4) Vesta? t Carry 1 , 2 by - - PowerPoint PPT Presentation

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Is there a magnetic field on asteroid (4) Vesta? t Carry 1 , 2 by - - PowerPoint PPT Presentation

Mar 29, 2023 264 likes •590 views

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion Is there a magnetic field on asteroid (4) Vesta? t Carry 1 , 2 by Beno in collaboration with: P. Vernazza (ESA/ESTEC), C. Dumas (ESO) & M. Fulchignoni

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SLIDE 1

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Is there a magnetic field on asteroid (4) Vesta? by Benoˆ ıt Carry1,2

in collaboration with:

  • P. Vernazza (ESA/ESTEC), C. Dumas (ESO) & M. Fulchignoni

(Obs. Paris)

1European Southern Observatory 2LESIA,Observatoire de Paris

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SLIDE 2

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Outline

  • 1. Why is (4) Vesta a highly interesting body ?
  • 2. Observations with SINFONI
  • 3. Mineralogy analysis
  • 4. Distribution of spectral slope
  • 5. Magnetic field?
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SLIDE 3

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Asteroid (4) Vesta

McFadden et al. (2008)

  • Second largest asteroid

⊲ Large crater at south pole ⊲ Parent body of Vestoids

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SLIDE 4

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Asteroid (4) Vesta

Vernazza et al. (2006)

  • Second largest asteroid

⊲ Large crater at south pole ⊲ Parent body of Vestoids

  • Composition

⊲ Mostly similar to HED meteorites ⊲ Unweathered???

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SLIDE 5

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Asteroid (4) Vesta

Binzel et al. (1997)

  • Second largest asteroid

⊲ Large crater at south pole ⊲ Parent body of Vestoids

  • Composition

⊲ Mostly similar to HED meteorites ⊲ Unweathered???

  • Albedo

⊲ Strong variations ⊲ Lava flow? ⊲ Composition? ⊲ Space weathering?

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SLIDE 6

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

0.2 0.4 0.6 0.8 Reflectance at 0.55 µm

  • 0.3
  • 0.2
  • 0.1
  • 0.0

0.1 0.2 0.3 0.4 Slope (0.4-2.4 µm) Strong SW signature on Vesta Slope: 0.145

SW

Howardite Eucrite Diogenite

V 4038

B0 B1

Grain size

  • V: Vesta
  • 4038: Vestoid (4038) Kristina
  • B0: Bereba before irradiation
  • B0: Bereba after irradiation
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SLIDE 7

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Observations

  • Aug. & Oct. 2004

⊲ Science Verification ⊲ Reduction’s a pain ⊲ J & H+K: 1.1-2.4 µm

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SLIDE 8

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Observations

  • Aug. & Oct. 2004

⊲ Science Verification ⊲ Reduction’s a pain ⊲ J & H+K: 1.1-2.4 µm

  • Observing conditions

⊲ φ ∼ 0.55′′ ⊲ Southern hemisphere ⊲ 14% surface

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SLIDE 9

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Observations

  • Aug. & Oct. 2004

⊲ Science Verification ⊲ Reduction’s a pain ⊲ J & H+K: 1.1-2.4 µm

  • Observing conditions

⊲ φ ∼ 0.55′′ ⊲ Southern hemisphere ⊲ 14% surface

  • Spatial resolution

⊲ Smallest spaxel (0.025′′) ⊲ FoV: 0.8×0.8 arcsec ⊲ Θ 92, 144, 371 km !!

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SLIDE 10

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Observations

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SLIDE 11

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Mineralogy

  • Compare to laboratory

⊲ HED meteorites ⊲ Fit band wings

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SLIDE 12

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Mineralogy

  • Compare to laboratory

⊲ HED meteorites ⊲ Fit band wings

  • Composition

⊲ Howardite-like ⊲ Steady over longitude ⊲ N-S trend ⊲ Diogenite spot at (180◦, -25◦)

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SLIDE 13

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Spectral slope distribution

  • Slope distribution

⊲ E-W trend ⊲ Consistent with HST

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SLIDE 14

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Spectral slope distribution

  • Slope distribution

⊲ E-W trend ⊲ Consistent with HST

  • Relationship
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SLIDE 15

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Spectral slope distribution

  • Slope distribution

⊲ E-W trend ⊲ Consistent with HST

  • Relationship

⊲ Mineral - Slope: No

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SLIDE 16

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Spectral slope distribution

  • Slope distribution

⊲ E-W trend ⊲ Consistent with HST

  • Relationship

⊲ Mineral - Slope: No ⊲ Mineral - Albedo: No

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SLIDE 17

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Spectral slope distribution

  • Slope distribution

⊲ E-W trend ⊲ Consistent with HST

  • Relationship

⊲ Mineral - Slope: No ⊲ Mineral - Albedo: No ⊲ Mineral - Topo: No

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SLIDE 18

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Spectral slope distribution

  • Slope distribution

⊲ E-W trend ⊲ Consistent with HST

  • Relationship

⊲ Mineral - Slope: No ⊲ Mineral - Albedo: No ⊲ Mineral - Topo: No ⊲ Albedo - Topo: No

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SLIDE 19

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Spectral slope distribution

  • Slope distribution

⊲ E-W trend ⊲ Consistent with HST

  • Relationship

⊲ Mineral - Slope: No ⊲ Mineral - Albedo: No ⊲ Mineral - Topo: No ⊲ Albedo - Topo: No ⊲ Albedo - Slope: so so

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SLIDE 20

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Spectral slope distribution

  • Slope distribution

⊲ E-W trend ⊲ Consistent with HST

  • Relationship

⊲ Mineral - Slope: No ⊲ Mineral - Albedo: No ⊲ Mineral - Topo: No ⊲ Albedo - Topo: No ⊲ Albedo - Slope: so so ⊲ Slope - Topo: so so

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SLIDE 21

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Spectral slope distribution

  • Slope distribution

⊲ E-W trend ⊲ Consistent with HST

  • Relationship

⊲ Mineral - Slope: No ⊲ Mineral - Albedo: No ⊲ Mineral - Topo: No ⊲ Albedo - Topo: No ⊲ Albedo - Slope: so so ⊲ Slope - Topo: so so

  • Resume
  • a. Unweathered
  • b. Strong albedo variations
  • c. Correlation Slope-Albedo
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SLIDE 22

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Several scenarios

  • 1. Composition or grain size inhomogeneity

⊕ Albedo variations ⊖ Unweathered aspect

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SLIDE 23

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Several scenarios

  • 1. Composition or grain size inhomogeneity

⊕ Albedo variations ⊖ Unweathered aspect

  • 2. Continuous bombardment by small meteorites

⊲ Ejected during big impact & stayed inside Hill sphere ⊕ Unweathered aspect ⊖ Albedo variations

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SLIDE 24

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Several scenarios

  • 1. Composition or grain size inhomogeneity

⊕ Albedo variations ⊖ Unweathered aspect

  • 2. Continuous bombardment by small meteorites

⊲ Ejected during big impact & stayed inside Hill sphere ⊕ Unweathered aspect ⊖ Albedo variations

  • 3. Vestaquake from large crater relaxation

⊕ Unweathered aspect ⊖ Lack of correlation between topography & spectral slope ⊖ Albedo variations

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SLIDE 25

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Magnetic field scenario

Blewett et al. (2007)

  • Surface magnetism

⊲ Crustal / Localized ⊲ Remnant ⊲ 0.2 nT ⊲ 10−3 Moon’s & 10−5 Earth’s

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SLIDE 26

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Magnetic field scenario

Blewett et al. (2007)

  • Surface magnetism

⊲ Crustal / Localized ⊲ Remnant ⊲ 0.2 nT ⊲ 10−3 Moon’s & 10−5 Earth’s

  • Like on the Moon

⊲ CUPS / Swirls ⊲ Albedo variation ⊲ Unweathered

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SLIDE 27

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Magnetic field scenario

Blewett et al. (2007)

  • Surface magnetism

⊲ Crustal / Localized ⊲ Remnant ⊲ 0.2 nT ⊲ 10−3 Moon’s & 10−5 Earth’s

  • Like on the Moon

⊲ CUPS / Swirls ⊲ Albedo variation ⊲ Unweathered

  • Detection

⊲ Slope-Albedo ⊲ w/o Topography ⊲ w/o Mineralogy

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SLIDE 28

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Observing limitations

  • 1. Spectral range

⊲ Slope: J= 1.17-1.32 µm ⊲ Mineral: H+K= 1.5-2.4 µm ⊲ Limited to pyroxexes ⊲ Other compounds?

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SLIDE 29

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Observing limitations

  • 1. Spectral range

⊲ Slope: J= 1.17-1.32 µm ⊲ Mineral: H+K= 1.5-2.4 µm ⊲ Limited to pyroxexes ⊲ Other compounds?

  • 2. Spatial resolution

⊲ Θ ≥ 90 km ⊲ Largest swirl on Moon: RGF = 100 km ⊲ Fine structure unobservable

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SLIDE 30

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Observing limitations

  • 1. Spectral range

⊲ Slope: J= 1.17-1.32 µm ⊲ Mineral: H+K= 1.5-2.4 µm ⊲ Limited to pyroxexes ⊲ Other compounds?

  • 2. Spatial resolution

⊲ Θ ≥ 90 km ⊲ Largest swirl on Moon: RGF = 100 km ⊲ Fine structure unobservable

  • 3. Spatial coverage

⊲ 14% of total surface ⊲ Dark hemisphere

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SLIDE 31

Asteroid (4) Vesta SINFONI Mineralogy Spectral slope Magnetic field Conclusion

Conclusions

  • Fist disk-resolved spectroscopy of an asteroid ever!

⊲ Spatial resolution is the key ⊲ Deconvolution algorithm ?

  • Magnetic field scenario

⊲ Explain both albedo and spectral slope ⊲ Suggested by current data ⊲ Require more observations

  • NASA Dawn mission

⊲ Arrival 2011 ⊲ No magnetometer ⊲ Spatial resolution ∼100 m ⊲ Spectral range 1-5 µm