June 10, 2011

Some Asteroids Contain Life Building Ingredients

According to a new discovery, some asteroids may have been like "molecular factories" cranking out life's ingredients and shipping them to Earth through meteorite impacts. 

The research team analyzed samples of a meteorite that landed on Tagish Lake in northern British Columbia in 2000. 

Variations in the geology of the meteorite samples were visible to the naked eye and indicated the asteroid had gone through substantial changes.

The team looked for variations in the organic chemistry that corresponded with variations in the meteorite's geology. 

Chris Herd, a University of Alberta geologist who led the research, said they found a surprising correlation, which gave researchers a snapshot of the process that altered the composition of organic material carried by the asteroid.

Herd said the findings show the importance of asteroids to Earth's history.

"The mix of prebiotic molecules, so essential to jump-starting life, depended on what was happening out there in the asteroid belt," Herd said in a statement. "The geology of an asteroid has an influence on what molecules actually make to the surface of Earth."

He said when the asteroid was created by the accumulation of dust around the infant sun it contained ice.  The ice then warmed and turned into water, which began perculating and altering the organic compounds buried in the rock.

The meteorite is rich in carbon and contained an assortment of organic matter including amino acids, which are the building blocks of proteins. 

Proteins are used by life to build structures like hair and nails.

"We see that some pieces have 10 to 100 times the amount of specific amino acids than other pieces," Dr. Daniel Glavin of NASA Goddard, a co-author on the Science paper, said in a statement. "We've never seen this kind of variability from a single parent asteroid before. Only one other meteorite fall, called Almahata Sitta, matches Tagish Lake in terms of diversity, but it came from an asteroid that appears to be a mash-up of many different asteroids."

The meteorite is considered to be one-of-a-kind because of its landing and handling.  It was January when the meteorite landed on the frozen, snow-covered lake. 

The individual who recovered the Tagish Lake meteorite consulted with experts beforehand and avoided any contamination issues.

"The first Tagish Lake samples -- the ones we used in our study that were collected within days of the fall -- are the closest we have to an asteroid sample return mission in terms of cleanliness," Dr. Michael Callahan of NASA's Goddard Space Flight Center in Greenbelt, Md., a co-author on the paper, said in a statement.

Herd said the meteorite's pristine state enabled the breakthrough research.

"The variations in the organic makeup are true to what was happing inside the asteroid," Herd said in a statement. "This is exactly what has been orbiting in the asteroid belt for the last 4.5 billion years."

The study is published June 10 in the journal Science.


Image Caption: This is one of the Tagish Lake meteorite fragments. Credit: Michael Holly, Creative Services, University of Alberta.


On the Net: