Dusty nursery bears baby comets
Ice spied in particles circling young stars.
31 May 2004
MARK PEPLOW

The dusty disks that swirl around new stars contain some of the building
blocks for life, NASA scientists confirmed last week. The disks create the
first seeds for planets and also comprise the starting materials for comets.

Images from the Spitzer Space Telescope provide the first unambiguous proof
that these clouds contain water ice, methanol and carbon dioxide. Some of
the bodies that form from this soupy mixture will be large dirty snowballs,
effectively the cores of comets, says Iwan Williams, an astronomer from
Queen Mary, University of London.

This is the first time that astronomers have actually seen inside a comet's
birthplace, says Alan Boss, an astrophysicist at the Carnegie Institution of
Washington.

Although planets forming at the outskirts of the disk will remain cold
enough to retain these molecules, the inner rocky planets will be much
hotter, and will lose their water and lighter carbon compounds as they form.
Still, subsequent collisions with the snowballs could supply such Earth-like
planets with some of the bare chemical necessities of life.

"Finding these molecules is not surprising," says Boss, "but
it is very
gratifying to find that our ideas were correct." Williams agrees:
"It's nice
to find ice out there. Water is actually surprisingly difficult to detect
from Earth."

Dan Watson and William Forrest from the University of Rochester, New York,
used Spitzer to gather infrared radiation coming from the dust that churns
around five very young stars in the constellation of Taurus, about 420 light
years from Earth. Most infrared light cannot be observed from the ground as
it is blocked by the Earth's atmosphere.

They analysed the spectrum of radiation coming from the dust, and identified
absorption patterns of water, methanol and carbon dioxide. They will publish
their research in a forthcoming issue of the Astrophysical Journal
Supplement Series.

Read the rest at Nature
http://www.nature.com/nsu/040524/040524-11.html

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