[meteorite-list] 'Bumpy Space Dust' Explains Origin of Most Common Molecule in Universe

[Ron Baalke]

http://researchnews.osu.edu/archive/molhydro.htm

[Embargoed for release until 4:00 PM ET on Thursday, June 23, 2005, to
coincide with presentation at the 60th Annual International Symposium on
Molecular Spectroscopy
<http://molspect.chemistry.ohio-state.edu/symposium/>.]


'BUMPY SPACE DUST' EXPLAINS ORIGIN OF MOST COMMON MOLECULE IN UNIVERSE
Ohio State University
June 23, 2005

COLUMBUS , Ohio -- Science fiction writer Harlan Ellison once said that
the most common elements in the universe are hydrogen and stupidity.

While the verdict is still out on the volume of stupidity, scientists
have long known that hydrogen is indeed by far the most abundant element
in the universe. When they peer through their telescopes, they see
hydrogen in the vast clouds of dust and gas between stars -- especially
in the denser regions that are collapsing to form new stars and planets.

But one mystery has remained: why is much of that hydrogen in molecular
form -- with two hydrogen atoms bonded together -- rather than its
single atomic form? Where did all that molecular hydrogen come from?
Ohio State University researchers recently decided to try to figure it out.

They discovered that one seemingly tiny detail -- whether the surfaces
of interstellar dust grains are smooth or bumpy -- could explain why
there is so much molecular hydrogen in the universe. They reported their
results at the 60th International Symposium on Molecular Spectroscopy,
held at Ohio State University .

Hydrogen is the simplest atomic element known; it consists of just one
proton and one electron. Scientists have always taken for granted the
existence of molecular hydrogen when forming theories about where all
the larger and more elaborate molecules in the universe came from. But
nobody could explain how so many hydrogen atoms were able to form
molecules -- until now.

For two hydrogen atoms to have enough energy to bond in the cold reaches
of space, they first have to meet on a surface, explained Eric Herbst,
Distinguished University Professor of physics at Ohio State.

Though scientists suspected that space dust provided the necessary
surface for such chemical reactions, laboratory simulations of the
process never worked. At least, they didn't work well enough to explain
the full abundance of molecular hydrogen that scientists see in space.

Herbst, professor of physics, chemistry, and astronomy, joined with
Herma Cuppen, a postdoctoral researcher, and Qiang Chang,
a doctoral student, both in physics, to simulate different dust surfaces
on a computer. They then modeled the motion of two hydrogen atoms
tumbling along the different surfaces until they found one another to
form a molecule.

Given the amount of dust that scientists think is floating in space, the
Ohio State researchers were able to simulate the creation of the right
amount of hydrogen, but only on bumpy surfaces.

When it comes to making molecular hydrogen, the ideal microscopic host
surface is "less like the flatness of Ohio and more like a Manhattan
skyline," Herbst said.

The problem with past simulations, it seems, is that they always assumed
a flat surface.

Cuppen understands why. "When you want to test something, starting with
a flat surface is just faster and easier," she said

She should know. She's an expert in surface science, yet it still took
her months to assemble the bumpy dust model, and she's still working to
refine it. Eventually, other scientists will be able to use the model to
simulate other chemical reactions in space.

In the meantime, the Ohio State scientists are collaborating with
colleagues at other institutions who are producing and using actual
bumpy surfaces that mimic the texture of space dust. Though real space
dust particles are as small as grains of sand, these larger, dime-sized
surfaces will enable scientists to test whether different textures help
molecular hydrogen to form in the lab.

#

Contact: Eric Herbst, (614) 292-6951; Herbst.6 at osu.edu

Herma Cuppen, (614) 292 4492; Cuppen.1 at osu.edu 

Written by Pam Frost Gorder, (614) 292-9475; Gorder.1 at osu.edu