Elsevier

Icarus

Volume 94, Issue 1, November 1991, Pages 218-231
Icarus

Asteroid 4 Vesta: Simultaneous visible and ultraviolet IUE observations

https://doi.org/10.1016/0019-1035(91)90152-JGet rights and content

Abstract

On 6–7 October 1990, 16 long-wavelength primary camera (LWP) spectra were recorded with the long-wavelength primary spectrograph of the International Ultraviolet Explorer (IUE) to obtain the resolved UV lightcurve of asteroid 4 Vesta. Simultaneously, the fine error sensor (FES) of the telescope was used to obtain Vesta's near-B lightcurve. Deep LWP and short-wavelength primary camera (SWP) spectra were also collected to establish the reflectivity curve of Vesta in the 1700–3200 Å region. The FES data show that the rotation period is of the order of 5 hr; combined with an old observation obtained in similar geometrical conditions, we derive a new, accurate value of the rotation period, 0.22258840 ± 8 × 10−8 day. Thus, our observations were obtained during three consecutive revolutions of the asteroid about its axis. The UV and optical lightcurves have one single minimum and one single maximum. The shape of the UV reflectivity curves is constant with rotational phase at the 3–5% level between 2600 and 3000 Å. The UV spectrum is redder than that of the Sun. The asteroid albedo increases linearly with wavelength from 2300 to 3000 Å, and this characteristic probably holds over the entire 2000–3500 Å range; its value near 2700 Å is 7.5% and it does not exceed ≈4% at 2000 Å. The intrinsic amplitude of Vesta's lightcurve is of the order of 10% and does not vary with wavelength from UV to near-IR. The present observations are compared with existing data to develop a self-consistent picture of Vesta's surface properties. No true large-scale and large-amplitude absorptions are observed in the 0.2–2.5 μm range. Small-amplitude colored features are observed at all phases: they seem to be part of a progressive and extended color change that renders one hemisphere slightly bluer than the other.

References (41)

  • R.C. Taylor et al.

    The rotation period and pole orientation of asteroid 4 Vesta

    Icarus

    (1985)
  • J.K. Wagner et al.

    Atlas of reflectance spectra of terrestrial, lunar, and meteoritic powders and frosts from 92 to 1800 nm

    Icarus

    (1987)
  • M. Barylak et al.

    FES sensitivity changes

    IUE NASA Newslett.

    (1985)
  • J.F. Bell et al.

    Asteroids: The big picture

  • E. Bowell et al.

    Magnitudes, colors, types and adopted diameters of the asteroids

  • E. Bowell et al.

    Colorimetry and magnitudes of asteroids

  • J.H. Carver et al.

    Comparison of lunar ultraviolet reflectivity with that of terrestrial rocks samples

    Moon

    (1975)
  • A. Cassatella et al.

    Revision of the absolute calibration of the LWP camera in low dispersion

    IUE NASA Newslett.

    (1983)
  • A. Cellino et al.

    Vesta's shape, density and albedo features

    Astron. Astrophys.

    (1989)
  • J. Degewij et al.

    Asteroid surface variegation

  • Cited by (9)

    • Olivine or impact melt: Nature of the "Orange" material on Vesta from Dawn

      2013, Icarus
      Citation Excerpt :

      Vesta is the largest differentiated asteroid with a basaltic surface that is mostly intact today. Since 1929, Vesta’s surface has been extensively studied using ground-based telescopes in the ultraviolet, visible and infrared wavelength ranges (Bobrovnikoff, 1929; McFadden et al., 1977; Blanco and Catalano, 1979; Taylor et al., 1985; Festou et al., 1991; Gaffey, 1997; Hendrix et al., 2003; Zellner et al., 2005; Rivkin et al., 2006; Reddy et al., 2010) and using Hubble Space Telescope (HST) data (Thomas et al., 1997; Li et al., 2010, 2011). All these studies led to a better understanding of the mineralogy, space weathering effects and the global shape of Vesta.

    • Ultraviolet spectroscopy of Asteroid (4) Vesta

      2011, Icarus
      Citation Excerpt :

      In orbit around it, Dawn will perform a detailed survey of its surface characteristics, internal structure, and elemental abundance targeted to understanding its formation and evolution (Russell et al., 2007). Rotationally resolved IUE observations showed single-peaked rotational lightcurves in the UV from 240 nm to 320 nm (Festou et al., 1991; Hendrix et al., 2003). The UV albedo of Vesta is less than 0.10, much lower than its visible albedo of ∼0.37 (Schevchenko and Tedesco, 2006).

    View all citing articles on Scopus

    Partially based on IUE observations obtained at Villafranca del Castillo, Spain.

    Guest observer with the International Ultraviolet Explorer Observatory

    Permanent address; Observatoire Midi-Pyrénées, 14 avenue E. Belin, URA 285 du CNRS, F-31400 Toulouse, France

    View full text