The Elemental Composition of Asteroid 433 Eros: Results of the NEAR-Shoemaker X-ray Spectrometer

Abstract

We report major element composition ratios for regions of the asteroid 433 Eros imaged during two solar flares and quiet sun conditions during the period of May to July 2000. Low aluminum abundances for all regions argue against global differentiation of Eros. Magnesium/silicon, aluminum/silicon, calcium/silicon, and iron/silicon ratios are best interpreted as a relatively primitive, chondritic composition. Marked depletions in sulfur and possible aluminum and calcium depletions, relative to ordinary chondrites, may represent signatures of limited partial melting or impact volatilization.

Global Mg/Si and Al/Si Distributions on the Lunar Surface Derived from Chang'E-2 X-ray Spectrometer

“…Thomas et al (1985) and Garcia (1994) have published methods for calculating solar plasma temperature from GOES data. This model was used by Trombka et al (2000) and Nittler et al (2001) in the NEAR-Shoemaker XRS papers to interpret the elemental composition of asteroid 433 Eros and also adopted in CE-1 XRS data analysis by Peng (2009) . The relationship between solar plasma temperature and the solar flux ratio (SFR) was obtained by fitting method (Peng 2009).…”

“…X-ray spectroscopy is considered as one of the most effective method among all remote sensing techniques to study the major elements abundance on the airless planetary surface, such as the Moon, Mercury, and asteroids (Adler et al 1973;Clark & Trombka 1997;Trombka et al 2000;Grande et al 2003;Sun et al 2008;Nittler et al 2011). In this technique, the solar X-rays interact with the planetary's surface materials producing characteristic X-ray fluorescences at the uppmost surface layer.…”

Laboratory experiments of particle size effect in X-ray fluorescence and implications to remote X-ray spectrometry of lunar regolith surface

“…Major elemental mapping in planets can be carried out with concurrent observation of X-rays from the Sun and the planet, as was proven in the Apollo 15 and 16 missions (e.g., Adler and Trombka, 1977). This method has also been used in planetary missions such as the Near-Earth Asteroid Rendezvous-Shoemaker (Trombka et al, 2000;Nittler et al, 2001), Hayabusa , and SMART-1 (Kellett et al, 2006;Grande et al, 2007).…”

The NEAR‐Shoemaker x‐ray/gamma‐ray spectrometer experiment: Overview and lessons learned

“…Compositional data were collected over a range of orbits, and the first x-ray signal from the surface of Eros was detected while NEAR was still in a 100 km orbit (Trombka et al, 2000b). The best quality compositional data were acquired during low altitude orbits.…”

“…These are the NaI(T1) raw spectrum (without either coincidence or anticoincidence); the BGO raw spectrum; the NaI(TI) spectrum in anticoincidence with BGO; the NaI(TI) spectrum in coincidence with the BGO 0.5 11 MeV line; and the NaI(T1) spectrum in coincidence with the BGO 1.022 MeV line. The nominal integration time for the GRS system was 1200 s, although it could be vaned from 1 s to -1 8 h. Details of the design of the detector systems can be found in Trombka et al (1997) and Goldsten et 01. (1 997).…”