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<p class="MsoNormal"><span style="font-size:11.0pt">Hi all,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">James Bryson
(University of Cambridge) will be giving this EAPS
Department Lecture Series seminar today at 4 pm in MIT
building 54-915. Refreshments at 3:45.<o:p></o:p></span></p>
<span style="font-size:11.0pt"><o:p></o:p></span>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:11.0pt">Constraints
on the timescales and distances of solid migration in the
solar nebula from meteorite palaeomagnetism<o:p></o:p></span></b></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Solid
objects ranging in size from the oldest mm-scale grains to
km-scale asteroids and even the terrestrial planets are
thought to have migrated throughout the early solar system.
Although these migrations have been proposed to have played
key roles in generating the present day architecture of the
solar system and forming planetary bodies, their timescales
and distances are poorly constrained. One reason for this
limited understanding stems from difficulties in recovering
the formation distances of meteorite components and parent
bodies from laboratory measurements. Models of our
protoplanetary disk indicate that the magnetic field it
supported decreased in intensity by orders of magnitude over
distances of tens of AU from the Sun. Hence, the intensity
of ancient magnetic fields recovered from magnetic
measurements of material old enough to have recorded a
magnetic remanence of this field could be used as a novel
method of constraining its formation distance. I will
present paleomagnetic results from two ancient meteorites
that indicate the distal formation (>10 AU) of their
parent bodies. I will use the distances I recover to support
at least one major planetary migration event during the
history of our solar system, the efficient outward transport
of mm-sized solids from the innermost solar system to >10
AU within ~3 Myr, and propose an explanation for a key trend
in the oxygen isotope composition of carbonaceous chondrites
that indicates the inward migration of distal ice to the
carbonaceous chondrite reservoir within the first ~3 - 4 Myr
of the solar system. Finally, I will use all of these
observations to place new constraints on the timescale of
the formation of Saturn's core and the accumulation of its
gaseous envelope.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p><br>
</o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p>Thanks</o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p>Ben
Weiss</o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p>benweiss.mit.edu<br>
</o:p></span></p>
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<p class="MsoNormal"><span
style="font-size:10.5pt;color:black">-- <o:p></o:p></span></p>
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<p class="MsoNormal"><span
style="font-size:10.5pt;color:black"><o:p> </o:p></span></p>
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