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VERSION:2.0
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METHOD:PUBLISH
BEGIN:VEVENT
DTSTART;TZID=Atlantic/Canary:20090618T000000
DTEND;TZID=Atlantic/Canary:20090618T010000
UID:iactalks-69
X-WR-CALNAME: IAC Talks: Open Astronomy Seminars
X-ORIGINAL-URL: /iactalks/Talks/view/69
CREATED:2009-06-18T00:00:00+01:00
X-WR-CALDESC: IAC Talks upcomming talks
SUMMARY:Asteroids as the parent bodies of meteorites: compositional
DESCRIPTION:Asteroids as the parent bodies of meteorites: compositional\nDr
 . Julia de León\n\nDue to their orbits, near-Earth asteroids (NEAs) have 
 been considered the most evident parent bodies of meteorites. Dynamical mo
 dels show that NEAs come primarily from the inner and central parts of the
  Main Belt (MB), and they reach their orbits by means of gravitational res
 onances (mainly ?6 and 3:1). This part of the MB is dominated by spectral 
 types S and Q, also the most common spectral types among the NEA populatio
 n (~60%), and correspond to objects composed of silicates. Their reflectan
 ce spectra show very characteristic absorption bands that can be used to i
 nfer their mineralogical composition applying different methods of analysi
 s. Those absorption bands are also present in the spectra of the most abun
 dant class of meteorites (~80%), the ordinary chondrites (OC).\n\nIn order
  to better understand the connection between MB asteroids, NEAs and OCs, w
 e undertook a spectroscopic survey of asteroids between 2002 and 2007, usi
 ng the telescopes and instrument facilities of "El Roque de los Muchachos"
  Observatory, in the Canary Islands. The survey contains visible and near-
 infrared spectra (0.5 - 2.5 µm) of a total of 105 asteroids. We have appl
 ied a method of mineralogical analysis based on spectral parameters to our
  sample of NEAs, and also to a sample of 91 MBs and 103 OCs obtained from 
 different databases. We have found some significant compositional differen
 ces between NEAs, MBs and OCs. The most remarkable one is that NEAs compos
 itionally differ from the whole set of OCs, and show a more olivine-rich c
 omposition, similar to what it is found for LL chondrites (only 8% of the 
 falls). This result suggests that S type NEAs are not the immediate precur
 sors of ordinary chondrites, as it was believed. We consider the size of t
 he objects as the key factor to explain this difference. NEAs are km-sized
  objects, while meteorites are meter tocm sized objects. Combining the inf
 ormation obtained from the dynamical models and the drift in semimajor axi
 s of the smaller objects due to their thermal intertia (Yarkovsky effect),
  we set out a possible scenario for the formation and the transport routes
  of NEAs and meteorites that could explain this compositional difference i
 n a plausible way.
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