Giant asteroids' 'smashing impact' helped evolution on Earth

A new study has found that giant asteroids' smashing the Earth's surface around 4 to 4.5 billion years ago, actually helped in its growth.

Researchers from academic and government institutions, including NASA's Solar System Exploration Research Virtual Institute (SSERVI) at NASA's Ames Research Center in Moffett Field, California, have brought forth a new terrestrial bombardment model, calibrated using existing lunar and terrestrial data, which sheds light on the role asteroid collisions played in the evolution of the uppermost layers of the early Earth during the geologic eon called the "Hadean".

Terrestrial planet formation models indicate Earth went through a sequence of major growth phases: initially accretion of planetesimals, planetary embryos, over many tens of millions of years, then a giant impact by a large proto-planet that led to the formation of our Moon, followed by the late bombardment when giant asteroids several tens to hundreds of miles in size periodically hit ancient Earth, dwarfing the one that killed the dinosaurs only 65 million years ago.

According to the researchers, prior to four billion years ago, Earth was resurfaced over and over by voluminous impact-generated melt. Furthermore, large collisions as late as about four billion years ago may have repeatedly boiled away existing oceans into steamy atmospheres. Despite the heavy bombardment, the findings are compatible with the claim of liquid water on Earth's surface as early as about 4.3 billion years ago based on geochemical data.

The new research reveals that asteroidal collisions not only severely altered the geology of the Hadean eon Earth, but likely also played a major role in the subsequent evolution of life on Earth as well.

Paper's lead author Simone Marchi said that the new picture of the Hadean Earth emerging from this work has important implications for its habitability.

The findings are published in the journal Nature.