[meteorite-list] Space Dust Carries Water and Organic Carbon

[Ron Baalke]

http://www.astrobio.net/exclusive/5986/space-dust-carries-water-and-organic-carbon

Space Dust Carries Water and Organic Carbon
Astrobiology Magazine
Johnny Bontemps
February 4, 2014

Summary: For the first time, scientists have detected water molecules 
on the surface of interplanetary dust particles. The findings open a new 
possibility about the delivery of life's ingredients to Earth and potentially 
elsewhere.

Could Space Dust have Delivered Life's Ingredients to Earth? 

For the first time, scientists have detected water molecules on the surface 
of interplanetary dust particles. The water forms in tiny bubbles when 
solar wind irradiates and damages the dust grains floating through space. 

Previous research had shown that space dust also contains organic carbon--another 
key ingredient for life. Taken together, these findings raise the intriguing 
possibility that dust trickling down from space could have seeded life's 
building blocks on our own planet--and potentially elsewhere. 

Dust in the (Solar) Wind 

For the past 40 years, researchers have debated whether solar wind could 
actually produce water. When astronauts brought rocks and soil back from 
the Moon, scientists had noticed that solar wind irradiation creates pockets 
of damage on the outer layers of space objects that lack a protective 
atmosphere. 

They quickly realized that water could potentially be created by this 
process. Dust grains come from the breakdown of comets, asteroids, and 
leftover debris from the birth of the solar system. They contain a lot 
of silicate, a mineral made of silicon and oxygen. 

Solar wind mainly blasts clouds of hydrogen ions into space. When the 
wind hits cosmic debris, the ensuing damage loosens the oxygen atoms, 
which are then free to react with the solar wind's hydrogen, potentially 
resulting in the formation of tiny pockets of water. 

But the amount of water was too small to be detected--until now. 

The research team, led by John Bradley of the University of Hawaii in 
Honolulu, used a state-of-the-art transition electron microscope to finally 
detect these water pockets on cosmic dust. The samples had previously 
been collected by high-flying NASA aircrafts, and curated by the Astromaterial 
research group at the NASA Johnson Space Center. 

The team confirmed their finding by simulating the process in the laboratory. 
The work was conducted at the Lawrence Livermore National Laboratory in 
California, and the findings were published this month is the journal 
Proceedings of the National Academy of Sciences. 

Seeds of Life? 

The findings open a new intriguing possibility about the origins of life 
on Earth. Some theories had suggested that life was seeded on Earth by 
comets or asteroids bombarding the early Earth's surface, before the planet 
got its protective atmosphere. 

"Our work shows that it could have been a much more gentle process, with 
this fine dust trickling down gently, carrying both organic carbon and 
water," says Hope Ishii, a co-author of the study now at the University 
of Hawaii in Honolulu. 

"In the process of entering the earth's atmosphere, the dust grains are 
heated. So the dust particles may act like little incubators for chemical 
reactions, like localized vessels carrying organic compounds and water 
together." 

But the findings do not suggest that Earth's oceans were formed by this 
process. 

Today, our Earth accumulates 30,000 to 40,000 tons of space dust every 
year. But that amount is hard to estimate overtime. "The amount of dust 
falling from space was much larger in the early Earth history, "Ishii 
explains. "And our sun was also much brighter in the past." 

"We don't know how much water is produced by this method. There's just 
too many factors we'd have to estimate," she says. 

Universal Delivery

Could space dust have delivered life's ingredients to planets outside 
our solar system as well? 

"Anywhere there's dust, and anywhere a star generates solar wind, we should 
expect this water-forming process to happen," Ishii says. "It's such a 
tantalizing possibility--that this process may have contributed to the 
origins of life not only on Earth, but possibly elsewhere."