[meteorite-list] All heck breaks loose in early solar system

From: Darren Garrison <cynapse_at_meteoritecentral.com>
Date: Wed, 08 Oct 2008 10:56:28 -0400
Message-ID: <5dipe415a9uifvrrpujf9co5b2jt5gj6fo_at_4ax.com>

(for those of you who are language sensitive)

Timing on this seems about right for the Late Heavy Bombardment...


http://www.thaindian.com/newsportal/health/all-hell-broke-loose-less-than-a-billion-years-after-solar-system-formation-re-issue_100103612.html

?All hell broke loose? less than a billion years after solar system formation
(Re-Issue)
October 5th, 2008 - 11:30 am ICT by ANI -

Washington, Oct 5 (ANI): A two-year search to find the Kuiper Belt??s smallest
objects, located in the outer solar system, has returned empty handed,
bolstering theories that ?all hell broke loose? in the solar system just a few
hundred million years after it formed. According to a report in New Scientist,
the search in question, the Taiwanese-American Occultation Survey (TAOS), spent
two years periodically photographing portions of the sky to look for small
chunks of rock and ice orbiting beyond Neptune, in a region of the solar system
called the Kuiper Belt. The survey targeted Kuiper Belt objects (KBOs) with
sizes between 2 miles (3 km) and 17 miles (28 km). Since such objects are too
small to see directly, the survey watched for stars to dim as KBOs passed in
front of and occulted them. After accumulating more than 200 hours of data
watching for stellar flickers lasting a second or less, TAOS did not spot any
occultations. The smallest KBOs seen so far measure about 30 km across and were
found five years ago using the Hubble Space Telescope. But only a few were seen
- 25 times more of the small objects had been predicted based on the size
distribution of larger KBOs. The non-discovery of the outer solar system??s
tiniest residents has turned up nothing, suggesting that ?all hell broke loose?
in the solar system just a few hundred million years after it formed. The solar
system began as a disc of slowly rotating dust grains and gas. When the dust
grains collided, they stuck together, snowballing into ever-larger structures.
The collisions at these earliest times were gentle enough that ?they mostly led
to sticking rather than breaking up?, said Charles Alcock, director of the
Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts.
This sticky process is thought to explain the distribution of medium- and
large-sized KBOs. But less than a billion years after the solar system began to
form, ?something happened that moved a lot of these bodies around?, said Alcock.
The giant outer planets moved out of their initial orbits, scattering KBOs in
their wake like bowling pins. ?Basically, everything sits around for 700 million
years and then boom - all hell breaks loose,? Hal Levison of the Southwest
Research Institute in Boulder, Colorado, has previously said of the period.
?After that phase of planet migration, when two objects encountered each other,
they broke each other up,? Alcock said. ?Smaller KBOs are thought to have formed
during that more destructive phase of collisions,? he added. (ANI)



http://www.spaceflightnow.com/news/n0810/07kbo/

Outer solar system not as crowded as astronomers thought
HARVARD-SMITHSONIAN CENTER FOR ASTROPHYSICS RELEASE
Posted: October 7, 2008

CAMBRIDGE, Mass. - When a treasure hunt comes up empty-handed, the hunters are
understandably disappointed. But when astronomers don't find what they are
looking for, the defeat can provide as much information as a successful search.

The search in question, the Taiwanese-American Occultation Survey (TAOS), spent
two years periodically photographing portions of the sky to look for small
chunks of rock and ice orbiting beyond Neptune, in a region of the solar system
called the Kuiper Belt. The survey targeted Kuiper Belt objects (KBOs) with
sizes between 2 miles (3 km) and 17 miles (28 km).

Since such objects are too small to see directly, the survey watched for stars
to dim as KBOs passed in front of and occulted them. After accumulating more
than 200 hours of data watching for stellar flickers lasting a second or less,
TAOS did not spot any occultations.

The Kuiper Belt contains objects in a range of sizes: a few very large ones
(like the dwarf planets Pluto, Eris, Makemake and Haumea) and many more smaller
ones. The commonness of a given size tells us information about the history of
planet formation and dynamics. In particular, the size distribution of KBOs
reflects a history of agglomeration, in which colliding objects tended to stick
together, followed by destructive collisions, where collisional velocities were
high enough to shatter the rocks involved.

Astronomers questioned whether they would find more and more objects as sizes
decreased further, or whether the distribution leveled out. The fact that no
occultations were seen sets a stringent upper limit on the number density of
KBOs between 2 and 17 miles in diameter. The outer solar system hence appears
not as crowded as some theories suggest, perhaps because small KBOs have already
stuck together to form larger bodies or frequent collisions have ground down
small KBOs into even smaller bits below the threshold of the survey.

The paper announcing this result, co-authored by CfA director Charles Alcock,
was published in the October 1 issue of the Astrophysical Journal Letters. The
full list of co-authors is available from ApJL.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for
Astrophysics (CfA) is a joint collaboration between the Smithsonian
Astrophysical Observatory and the Harvard College Observatory. CfA scientists,
organized into six research divisions, study the origin, evolution and ultimate
fate of the universe.
Received on Wed 08 Oct 2008 10:56:28 AM PDT