Asteroids may have boosted life on Earth 3.9 billion years ago

May 21st, 2009 - 12:51 pm ICT by ANI  

Washington, May 21 (ANI): A new study has indicated that the bombardment of Earth by asteroids 3.9 billion years ago may have enhanced early life rather then wipe it out.

The study, by University of Colorado at Boulder researchers, determined that the bombardment of Earth nearly 4 billion years ago by asteroids as large as the US state of Kansas would not have had the firepower to extinguish potential early life on the planet and may even have given it a boost.

Impact evidence from lunar samples, meteorites and the pockmarked surfaces of the inner planets paints a picture of a violent environment in the solar system during the Hadean Eon 4.5 to 3.8 billion years ago, particularly through a cataclysmic event known as the Late Heavy Bombardment about 3.9 million years ago.

Although many believe the bombardment would have sterilized Earth, the new study shows it would have melted only a fraction of Earth’s crust, and that microbes could well have survived in subsurface habitats, insulated from the destruction.

“These new results push back the possible beginnings of life on Earth to well before the bombardment period 3.9 billion years ago,” said CU-Boulder Research Associate Oleg Abramov.

“It opens up the possibility that life emerged as far back as 4.4 billion years ago, about the time the first oceans are thought to have formed,” he added.

The researchers used data from Apollo moon rocks, impact records from the moon, Mars and Mercury, and previous theoretical studies to build three-dimensional computer models that replicate the bombardment.

Abramov and CU-Boulder geological sciences Professor Stephen Mojzsis plugged in asteroid size, frequency and distribution estimates into their simulations to chart the damage to the Earth during the Late Heavy Bombardment, which is thought to have lasted for 20 million to 200 million years.

The 3-D models allowed Abramov and Mojzsis to monitor temperatures beneath individual craters to assess heating and cooling of the crust following large impacts in order to evaluate habitability.

The study indicated that less than 25 percent of Earth’s crust would have melted during such a bombardment.

“Even under the most extreme conditions we imposed, Earth would not have been completely sterilized by the bombardment,” said Abramov.

Instead, hydrothermal vents may have provided sanctuaries for extreme, heat-loving microbes known as “hyperthermophilic bacteria” following bombardments, said Mojzsis.

Even if life had not emerged by 3.9 billion years ago, such underground havens could still have provided a “crucible” for life’s origin on Earth, Mojzsis added. (ANI)

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