Complex Water-ice Mixtures on NII Nereid: Constraints from NIR Reflectance

Benjamin N.L. Sharkey, Vishnu Reddy, Juan A. Sanchez, Matthew R.M. Izawa, Walter M. Harris

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Nereid, Neptune's third-largest satellite, lies in an irregular orbit and is the only outer satellite in the system (apart from Triton) that can be spectroscopically characterized with the current generation of Earth-based telescopes. We report our results on the spectral characterization of Nereid using its reflectance spectrum from 0.8 to 2.4 μm, providing the first measurements over the range of 0.8-1.4 μm. We detect spectral absorption features of crystalline water ice in close agreement with previous measurements. We show that model fits of simple intimate mixtures including water ice do not provide simultaneous matches to absorption band depths at 1.5 and 2.0 μm when accounting for the spectral continuum. Possible solutions include invoking a more complex continuum, including both crystalline and amorphous water ice, and allowing for submicron-sized grains. We show that mixtures including magnetite and the CM2 chondrite Murchison provide a flexible framework for interpreting spectral variation of bodies with neutral-sloped spectra like that of Nereid. Magnetite in particular provides a good match to the spectral continuum without requiring the presence of tholin-like organics. We note that carbonaceous chondrites and their components may be useful analogs for the non-ice components of outer solar system bodies, consistent with recent findings by Fraser et al. Comparison to spectra of large trans-Neptunian objects and satellites of Uranus show that Nereid's low albedo, deep water bands, and neutral color is distinct from many other icy objects, but such comparisons are limited by an incomplete understanding of spectral variability among ∼100 km-sized icy bodies 2021. The Author(s). Published by the American Astronomical Society.

Original languageEnglish (US)
Article number143
JournalPlanetary Science Journal
Issue number4
StatePublished - Aug 2021


  • Irregular satellites (2027)
  • Natural satellites (solar system) (1089)
  • Near infrared astronomy (1093)
  • Neptunian satellites (1098)
  • Small solar system bodies (1469)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Geophysics


Dive into the research topics of 'Complex Water-ice Mixtures on NII Nereid: Constraints from NIR Reflectance'. Together they form a unique fingerprint.

Cite this