Resemblance between Itokawa and Comet Hartley 2

Has anybody else noticed a resemblance between the asteroid Itokawa
and today's EPOXY photos of Comet Hartley 2? Both objects are of
similar size and show very rough, rubble strewn ends and yet very
smooth middle sections. Itokawa may indeed be a blown out comet,
while Hartley 2 seems to be in the prime of comet life.

But what is causing the dichotomy of extremely broken, rubbled vs.
very smooth surfaces for both of these objects? Is this a pattern
for things to come with a certain class of objects?

stargene wrote:
Has anybody else noticed a resemblance between the asteroid Itokawa
and today's EPOXY photos of Comet Hartley 2? Both objects are of
similar size and show very rough, rubble strewn ends and yet very
smooth middle sections. Itokawa may indeed be a blown out comet,
while Hartley 2 seems to be in the prime of comet life.

But what is causing the dichotomy of extremely broken, rubbled vs.
very smooth surfaces for both of these objects? Is this a pattern
for things to come with a certain class of objects?

Yes, lots of people have commented on this. There has been quite a
thread on Yahoogroup's Minor Planet Mailing List. The consensus is that
we're looking at the "Brazil nut effect" -- shake the bottle of mixed
nuts and the big ones rise to the top. Something hits the nucleus from
time to time, and the bigger rocks go to the regions of highest
potential while the smaller grains go to the regions of lowest
potential. Rotation dominates over gravity for something this small, so
the rocks wind up far from the axis of rotation and the grains wind up
close to it.

-- Bill Owen

Bill Owen ) writes:
stargene wrote:
Has anybody else noticed a resemblance between the asteroid Itokawa
and today's EPOXY photos of Comet Hartley 2? Both objects are of
similar size and show very rough, rubble strewn ends and yet very
smooth middle sections. Itokawa may indeed be a blown out comet,
while Hartley 2 seems to be in the prime of comet life.

But what is causing the dichotomy of extremely broken, rubbled vs.
very smooth surfaces for both of these objects? Is this a pattern
for things to come with a certain class of objects?

Yes, lots of people have commented on this. There has been quite a
thread on Yahoogroup's Minor Planet Mailing List. The consensus is that
we're looking at the "Brazil nut effect" -- shake the bottle of mixed
nuts and the big ones rise to the top. Something hits the nucleus from
time to time, and the bigger rocks go to the regions of highest
potential while the smaller grains go to the regions of lowest
potential. Rotation dominates over gravity for something this small, so
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^

What does this mean? Not that the rotational speed exceed the escape speed,
surely?

--John Park

the rocks wind up far from the axis of rotation and the grains wind up
close to it.

-- Bill Owen