How did Earth manage to hold onto its organics after being slammed by a Mars-sized object 4.4 billion years ago?

THE GIST

- Formaldehyde may be the delivery mechanism for organics on Earth -- and throughout the solar system.

- The finding is ironic since formaldehyde is poison to life as we know it.

- The discovery stems from analysis of samples from NASA's Stardust comet probe.

How baby Earth managed to keep hold of its organic matter after the clubbing it took by a Mars-sized object roughly 4.4 billion years ago has long puzzled scientists.

The throttling was so severe scientists believe Earth melted. Splatters that ended up in space eventually came together to form the moon. Lightweight materials, like water and carbon, would have vaporized. How then did the building blocks for life manage to survive?

Scientists think they have found the answer: The organics were locked in stable chains formed from formaldehyde, an ironic finding considering that formaldehyde ended up being poisonous to the very life it may have made possible.

"Formaldehyde is very interesting, very reactive. It can even react with itself and form complex polymers," George Cody, a senior scientist at the Carnegie Institution of Washington, told Discovery News.

Formaldehyde also is plentiful in molecular clouds in space, meaning ample quantities would have been around for incorporation into the solar system's population.

Two chains of evidence support this theory. First, organic solids have been found in meteorites and in comets. A sample from NASA's Stardust comet mission gave Cody and colleagues a sign they were on the right path.

"It was about the most chemically complex material I had ever seen in my life," Cody said.

Scientists then turned to lab work to reproduce the type of organic matter found in carbonaceous chondrites, a type of organic-rich meteorite, from formaldehyde. They found their formaldehyde-synthesized material was similar to what has been found in carbonaceous chondrites and from Comet Wild 2, which was sampled by NASA's Stardust probe.

The experiments also showed the organics would survive temperatures of up to 1,400 Centigrade (2,552 degrees Fahrenheit).

"The formaldehyde forms these little tiny organic balls," Cody said.

Other molecules found in space, such as hydrogen cyanide, also could polymerize with itself, but they fall apart in hot water, Cody added.

"Formaldehyde is almost unique in its tendency to hang out -- and hang on -- as the solar system got hotter and dryer," said Cody.

Also buttressing the team's findings is a related study showing that comets may be much more watery than previously thought.

"If liquid water environments were common, than there are a lot more places to produce pre-biotic material," Dante Lauretta, associate professor at the University of Arizona's Lunar and Planetary Laboratory, told Discovery News.

"Now that we know what we're working with, we want to understand the chemistry better," added Cody.

Cody's research was reported in the Proceedings of the National Academy of Sciences earlier this month. Lauretta's team, which also studied Stardust samples, is publishing in the online edition of the journal Geochimica et Cosmochimica Acta.