6 Hebe - Major Meteorite Source

Major Meteorite Source

6 Hebe is the probable parent body of the H chondrite meteorites and the IIE iron meteorites.

Remarkably, this would imply that it is the source of about 40% of all meteorites striking the Earth. Evidence for this connection includes the following (after Michael Gaffey and Sarah L. Gilbert.):

  • The spectrum of Hebe matches a mix of 60% H chondrite and 40% IIE iron meteorite material.
  • The IIE type are unusual among the iron meteorites, and probably formed from impact melt, rather than being fragments of the core of a differentiated asteroid.
  • The IIE irons and H chondrites likely come from the same parent body, due to similar trace mineral and oxygen isotope ratios.
  • Asteroids with spectra similar to the ordinary chondrite meteorites (accounting for 85% of all falls, including the H chondrites) are extremely rare.
  • 6 Hebe is extremely well placed to send impact debris to Earth-crossing orbits. Ejecta with even relatively small velocities (~280 m/s) can enter the chaotic regions of the 3:1 Kirkwood gap at 2.50 AU and the nearby secular resonance which determines the high-inclination edge of the asteroid belt at about 16° inclinations hereabouts.
  • Of the asteroids in this "well-placed" orbit, Hebe is the largest.
  • An analysis of likely contributors to the Earth's meteorite flux places 6 Hebe at the top of the list, due to its position and relatively large size. If Hebe is not the H-chondrite parent body, then where are the meteorites from Hebe?

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