To Be or Not to Be Iron

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Science  09 Jul 2004:
Vol. 305, Issue 5681, pp. 151
DOI: 10.1126/science.305.5681.151a

Analyses of comets, asteroids, meteorites, and interplanetary dust particles have suggested that magnesium-rich olivine (forsterite) comes from pristine, primordial objects like comets, whereas iron-rich olivine (fayalite) comes from the alteration (possibly by liquid water) of minerals on a planetesimal or asteroidal body. Observations of dusty disks around stars have found magnesium-rich olivine, but not an iron-rich signature of anything that might be considered a precursor to terrestrial-like exoplanets or asteroids.

Honda et al. report the detection of iron-rich olivine dust around the Vega-like star, HD145263, from high-resolution spectra obtained at the Subaru 8.2-m telescope. If their identification is correct, then HD145263 may have an asteroid belt like that of the current solar system or a number of planetesimals, such as those modeled for the early solar system. Collisions between the asteroids or planetesimals would create the dusty disk of debris around the star, yielding the observed signal of iron-rich olivine. — LR

Astrophys. J. 610, L49 (2004).

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