Visible spectroscopy of 2003 UB313: Evidence for N2 ice on the surface of the largest TNO?

Abstract

The recent discovery of two large trans-Neptunian objects (TNOs) 2003 UB313 and 2005 FY9, with surface properties similar to those of Pluto, provides an exciting new laboratory for the study of processes considered for Pluto and Triton: volatile mixing and transport; atmospheric freeze-out and escape, ice chemistry, and nitrogen phase transitions. We studied the surface composition of TNO 2003 UB313, the first known TNO larger than Pluto. We report a visible spectrum covering the 0.35-0.95 microns spectral range, obtained with the 4.2m William Herschel Telescope at "El Roque de los Muchachos" Observatory (La Palma, Spain). The visible spectrum of this TNO presents very prominent absorpt- ions bands formed in solid CH4. At wavelengths shorter than 0.6 micron the spectrum is almost featureless and slightly red (S'=4%). The icy-CH4 bands are significantly stronger than those of Pluto and slightly weaker than those observed in the spectrum of another giant TNO, 2005 FY9, implying that methane is more abundant on its surface than in Pluto's and close to that of the surface of 2005 FY9. A shift of 15 +/-3 A relative to the position of the bands of the spectrum of laboratory CH4 ice is observed in the bands at larger wavelengths (e.g. around 0.89 microns), but not at shorter wavelengths (the band around 0.73 microns is not shifted) this may be evidence for a vertical compositional gradient. Purer methane could have condensed first while 2003 UB313 moved towards aphelion during the last 200 years, and as the atmosphere gradually collapsed, the composition became more nitrogen-rich as the last, most volatile components condensed, and CH4 diluted in N2 is present in the outer surface layers.

Accepted in A&A

References in corpus (2)

• Discovery of a planetary-sized object in the scattered Kuiper belt
• Direct measurement of the size of 2003 UB313 from the Hubble Space Telescope

Cited by in corpus (19)

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• Evidence of N2-Ice On the Surface of the Icy Dwarf Planet 136472 (2005 FY9)
• 1I/'Oumuamua as an N2 ice fragment of an exo-Pluto surface: I. size and compositional constraints
• Ice Mineralogy Across and Into the Surfaces of Pluto, Triton, and Eris
• The spectrum of (136199) Eris between 350 and 2350 nm: Results with X-Shooter
• Moderate D/H Ratios in Methane Ice on Eris and Makemake as Evidence of Hydrothermal or Metamorphic Processes in Their Interiors: Geochemical Analysis
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• Rotationally resolved spectroscopy of dwarf planet (136472) Makemake
• The Diverse Solar Phase Curves of Distant Icy Bodies. II. The Cause of the Opposition Surges and Their Correlations
• Remote Sensing D/H Ratios in Methane Ice: Temperature-Dependent Absorption Coefficients of CH3D in Methane Ice and in Nitrogen Ice
• Digging Into the Surface of the Icy Dwarf Planet Eris
• JWST observations of stellar occultations by solar system bodies and rings
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• Long-term photometric monitoring of the dwarf planet (136472) Makemake
• Rotationally resolved spectroscopy of (20000) Varuna in the near-infrared