[meteorite-list] Los Alamos Scientists Hope Two Asteroids Offer Insight to the Origins of the Solar System (Dawn)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri Apr 21 11:52:41 2006
Message-ID: <200604202304.QAA23509_at_zagami.jpl.nasa.gov>

http://www.abqtrib.com/albq/nw_science/article/0,2668,ALBQ_21236_4633359,00.html

Los Alamos scientists hope two asteroids offer insight to the origins of
the solar system

By Sue Vorenberg
The Albuquerque Tribune
April 19, 2006

Trying to see what our solar system looked like before there were
planets is a bit like trying to find what was first drawn on a
20-year-old Etch A Sketch.

Volcanoes, plate tectonics, strikes from meteors and other geologic
activity has shaken the oldest rocks on planets like the Earth and Mars
so that almost nothing is left of the original asteroids and other
materials that formed them 4.5 billion years ago.

But there are a few places where the solar system's oldest rocks remain
and can give clues to what the solar system looked like before there
were planets.

Los Alamos National Laboratory has designed a gadget that will help the
National Aeronautics and Space Administration see the history of those
rocks after a new spacecraft travels to them.

The gadget, called GRAND, is part of the Dawn Mission, which will visit
Vesta and Ceres, the two biggest asteroids in the asteroid belt located
between Mars and Jupiter.

The mission - projected to cost between $425 million and $450 million -
has had a lot of starts and stops along the way since it was first
proposed in 1998. Last month, NASA decided to give final approval for it
to go forward.

The Dawn spacecraft is set for launch sometime between June and August
2007.

"Vesta is really interesting," said Tom Prettyman, a Los Alamos
scientist working on the mission. "It's thought to be the source of a
special type of meteorites found on Earth."

If scientists can confirm Vesta as the source of those meteorites, they
could study them as if they were samples returned from the asteroid,
Prettyman said.

The composition of those rocks - how much iron, magnesium and other
elements they have inside them - can tell scientists more about the
types of rocks floating around when the solar system first formed out of
debris in what scientists call a molecular cloud.

Los Alamos' GRAND - which stands for Gamma Ray and Neutron Spectrometer
for Dawn - is a shoe-box-sized, 30-pound detector that can see which
elements are present on the asteroids and how those elements are
interacting with radioactive forces in space.

The mission also includes instruments from Germany and Italy that will
collect other types of data and take pictures of the asteroids for
scientific analysis, Prettyman said.

Gathering data about the two asteroids, in turn, can help scientists
understand more about the early solar system, Prettyman said.

"The present thinking is that our solar system was formed from a giant
molecular cloud, very much like clouds you can see out there with the
Hubble Space Telescope," Prettyman said. "The thought is solar systems
form when a cloud is in the area of a giant supernova, and the supernova
essentially triggers the collapse of the cloud."

As the cloud collapses, material in it and elements from the supernova
bunch together into small clumps that, over millions of years, mash
together to form planets.

In the inner parts of the solar system, warmer and closer to the sun,
heavier elements such as iron, aluminum and magnesium form into rocky
planets like Earth, Venus and Mars.

In the outer parts of the solar system, where it's cold enough for
liquid water or solid water to form, gas giants made of clumped ice and
gasses form planets like Jupiter and Saturn.

Somewhere in between is what scientists call the dew line - the line
where rocky planets stop and icy planets start.

Prettyman and others theorize the dew line could be somewhere in the
asteroid belt between Ceres and Vesta, he said.

The study of both asteroids should give scientists a better
understanding of where the dew line is and what it looked like in the
early solar system.

The reason the rocks in the asteroid belt are so old and so ideal for
study is that the planet Jupiter - through its gravitational pull - has
kept debris in that area from merging into a planet. Jupiter formed in
the first 20 million years or so of the solar system's history, so the
thought is that rocks in that area are probably at least that old, said
Bruce Barraclough, another Los Alamos scientist working on the mission.

The study of our early solar system can also tell us a great deal about
how other solar systems are forming, and ultimately about the types and
scope of planets they might have, Prettyman said.

Asteroid survey got a rocky start

The first marker on the road to the oldest rocks in the solar system was
a telling one for Tom Prettyman, a scientist at Los Alamos National
Laboratory.

He was set to head off to Washington, D.C., to present his first report
on the lab's contribution to NASA's Dawn Mission - which will explore
two asteroids that are nearly 4.5 billion years old - when he hit what
looked like a big, depressing stop sign.

"I was supposed to report on our results on Sept. 12, 2001," Prettyman
said. "I had packed my bags, and it was the morning of the 11th. I was
dragging my bags down the hallway and saw on my TV that I wasn't going
to get on an airplane."

The Sept. 11 terrorist attacks stalled his presentation until that
December and marked the first in a series of starts and stops for the
mission, Prettyman said.

After his presentation, NASA went ahead with the mission. On Christmas
Eve 2003, NASA canceled the mission because an agency assessment didn't
think the craft could travel to both asteroids, Prettyman said.

In early 2004, NASA reinstated the mission after scientists found a way
to make the craft reach both asteroids and deal with concerns raised in
the assessment.

"We just marched toward launch from there," he said.

But then in July 2005, citing budget concerns, NASA again canceled the
mission.

"To get canceled when you're that close really breaks your heart," said
Bruce Barraclough, another Los Alamos scientist on the project.

This March, the coin flipped over again. NASA reinstated the mission
after being pressured by Italy and Germany, which both have instruments
on the craft, and by an independent assessment panel that found no
problems with the mission.

It is set to launch in summer 2007 - at the tail end of a launch window
that opens only every 17 years. That's how often the asteroids are close
enough together to make the mission feasible.

Dawn should reach Vesta in September 2011 and Ceres in February 2015,
Prettyman said.

"We're just glad we have a shot at it," Prettyman said.
Received on Thu 20 Apr 2006 07:04:25 PM PDT