[meteorite-list] Crashed Genesis Probe Delivers Solar Wind

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Mar 16 18:08:23 2006
Message-ID: <200603152014.k2FKETN01789_at_zagami.jpl.nasa.gov>

http://www.newscientistspace.com/article/dn8848-crashed-genesis-probe-delivers-solar-wind.html

Crashed Genesis probe delivers solar wind
Maggie McKee
New Scientist
15 March 2006

Solar wind ions salvaged from NASA's crashed Genesis space capsule could
yet help trace the primordial composition of the solar system,
fulfilling the mission's main goal, the mission's first scientific
results suggest.

But the task will not be easy - more than half of the samples appear too
damaged to be useful and the remaining ones are chemically contaminated
from the crash.

The Genesis capsule smashed into the ground in Utah on 8
September 2004 because of a design flaw that prevented its parachutes
from activating. It had spent 27 months in space collecting charged
particles blown from the Sun's outermost layer. That layer is thought to
reflect the composition of the gas-and-dust cloud, known as the solar
nebula, from which the solar system formed, about 4.6 billion years ago.

Scientists had hoped this primordial composition would provide a
baseline to understand how different planets and meteorites later
evolved such a wide range of isotopes of key elements such as oxygen and
nitrogen.

But the capsule's crash landing threw that possibility into question
after dirt from Utah's salt flats entered the ruptured science canister
and most of the delicate wafers on the mission's five collector arrays
shattered.
          
>From the ashes

However, mission members picked up the pieces, literally, and sought
novel ways to study the particles. Now, preliminary studies offer fresh
hope for the mission's science goals. They were reported on Tuesday at
the Lunar and Planetary Science Conference in Houston, Texas, US.

"The most important result is that we have results," says Don Burnett,
the mission's principal investigator at Caltech in Pasadena, US. "These
are our first steps in coming back from the ashes."

The mission's most important target was oxygen, which exists on
different planets and meteorites in bafflingly different ratios of its
three most common isotopes. Because the solar wind is 99% ions of
hydrogen and helium, mission planners designed an instrument to repel
these light elements and trap heavier ions such as oxygen at
concentrations at least 20 times greater than normally found in the
solar wind.
          
Scary finding

This instrument used a curved, electrically charged mirror to focus the
heavy ions onto a target made of several ultra-pure materials. But
because different isotopes of the same element react differently in an
electric field, they segregate in different concentrations at different
places on the target. So to get an accurate measurement of all the
isotopes, this separation effect needed to be calibrated.

Researchers used neon from the solar wind, a noble gas that is rare on
Earth, to try to understand exactly how this separation worked. At
first, the neon observations did not line up at all with predictions
made before the samples were returned. "We were quite scared," says
planetary scientist Rainer Wieler of the Swiss Federal Institute of
Technology in Zurich.

But then other team members developed a new theoretical model that
included data such as the spacecraft's measurement of the speed of the
solar wind. Now, the new model agrees with the observed neon
distribution with an uncertainty of a few percent. "We'd like it to be
better," says team member Ian Franchi of Open University in the UK. "But
it's an important step."

The calibration with neon is encouraging for the mission's main target,
says Wieler: "It suggests it should be possible to detect the oxygen
composition in the solar wind."

Three winds

Researchers were also anxious to know how well the samples collected by
Genesis actually traced the composition of the early solar system. For
this, they needed to understand how accurately the solar wind represents
the composition of the Sun's outermost layer and whether that layer, in
turn, has truly remained unchanged since the solar system formed from a
dusty nebula.

This is a complicated question, since there are actually three different
types of solar wind. Each moves at a different speed and may accelerate
different elements - and possibly different isotopes - by different
amounts, complicating the interpretation of the Sun's true composition.

Genesis used sensors to gauge the speed of the solar wind and then
deployed specific collectors to gather up particles from each of the
three types. The new studies show that regardless of the type of solar
wind measured, the ratio of neon isotopes collected did not vary. This
hints that the samples do indeed trace the composition of its outer
layer and that "what we measure in the Sun can apply to the solar
nebula", says Burnett.

Brown stain

The new research is especially heartening for the team because more than
half of the collectors smashed into pieces too tiny to study, and what
pieces remained were covered by what researchers call a "brown stain".

This stain was caused during the crash when the spacecraft released
molecules of gas, which then fused into long polymers on the collectors'
surfaces when exposed to ultraviolet light from the Sun.

The brown stain contains carbon and oxygen, contaminating the pristine
samples. But researchers have devised a number of ways to remove the
stain - such as using ozone to react with the polymers. Removing the
contamination is complicated and time-consuming, says Franchi: "But I
don't think anybody's saying we can't do this."

"In principle, we might be able to do everything we started out to do,"
agrees Burnett.
Received on Wed 15 Mar 2006 03:14:28 PM PST