Earth may have been the target of more asteroids and comets than once believed, based on a new computer simulation. These violent impacts may have boiled away oceans, sending vast quantities of water vapor into the atmosphere.

Astronomers have long known that collisions between minor bodies and planets occurred frequently in the early history of the solar system. This period is known as the Late Heavy Bombardment.

Southwest Research Institute researchers developed a computer simulation that models our planet during it first 500 million years. The virtual solar system was created using data taken of lunar and interplanetary craters. Erosion and other planetary processes have erased nearly all evidence on Earth of interplanetary impacts during the first half-billion years of our planet's history. This required researchers to study cratering patterns left on other worlds, including Mars and Mercury, in addition to our planetary companion.

The battered surface of the Moon provides a glimpse into the violent history of the Earth during its formation, the Hadean Eon. This was the first era of the Earth's formation, when the planet was still rapidly cooling, with a shallow crust. Researchers also examined the presence of minerals, believed to be brought from space, and their reactions with gold and other elements present in the crust of the Earth.

Recreation of the Hadean Eon suggested that in addition to a myriad of collisions with smaller objects, our planet was also likely struck by several large bodies. These may have provided enough energy to melt the surface of the young Earth, a process which could have been repeated many times, continually reforming the crust of the young planet. These tremendous energies would have boiled the oceans, releasing water into the air, where it would have resided for long periods before falling back to the surface as precipitation.

Such a process could explain why geologists are unable to find any rocks from this era.

"This paper shows the way for what will probably become a new thread in research on the environment and geology of the early Earth," Henry Melosh, a geophysicist at Purdue University, said.

This investigation was not the first to suggest that the Earth may have been subject to intense bombardment during its first half-billion years, but it is one of the most detailed simulations of its type ever developed. Comparisons between the terrestrial rocks and interplanetary cratering patterns provided detail unavailable in earlier studies.

Development of the simulation of the earliest history of the Earth was profiled in the journal Nature.

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