How did the Late Heavy Bombardment affect Earth’s crust?

Date:

Share post:

Astrobiologists supported by the NASA Astrobiology Institute have assessed the effects of impacts on the crust of the early Earth. The research could help determine whether or not evidence of such violent events in our planet’s early history could still be found in the geological record.

How did the Late Heavy Bombardment affect Earth's crust?
The process of collision and accretion created the four rocky, or terrestrial, planets of our inner
solar system — Mercury, Venus, Earth, and Mars [Credit: NASA Discovery Program]

During the first billion years after its formation, the inner solar system was crowded with debris. This resulted in frequent collisions, which not only played a role in the formation and evolution of planets like Earth and Mars, but also helped shape their potential to host life. Today, it is difficult to determine the details of how this ‘impact epoch’ affected the young planets.

The new study estimates the thermal effects of a period known as the Late Heavy Bombardment (LHB) on Earth. The LHB is hypothesized to have occurred roughly 3.9 billion years ago during the Hadean eon, and was a time when impacts were especially frequent. Heat generated by the impacts left up to 10 percent of the planet’s surface covered with melt sheets more than a kilometer thick. Ejecta and vaporized rock were sprayed into the air and deposited around the globe. Astrobiologists have long wondered if any evidence of LHB impacts could still remain in rocks left over from the Hadean (such as rocks from the Jack Hills in Australia).

To answer this question, the team of scientists focused on a mineral called zircon. Zircon contains lead, and this element can be removed from the mineral as it is melted and re-shaped by impacts.

The team used sophisticated models to determine whether or not zircons in Hadean rocks could contain signatures left over from the LHB based on the amount of lead they contain. They concluded that if these minerals indeed contain signatures of the LHB, they would have come from the impact ejecta (the materials tossed into the air by the violent collisions). Zircons in rocks at the surface of the planet would not likely have survived in the vast melt sheets.

The paper, “The impact environment of the Hadean Earth,” was published in the journal Chemie der Erde – Geochemistry.

Author: Aaron L. Gronstal | Source: Astrobio.net [February 24, 2014]

ADVERTISEMENT

spot_img

Related articles

Brown dwarfs found sprinkled among newborn stars in Orion Nebula

In an unprecedented deep survey for small, faint objects in the Orion Nebula, astronomers using NASA's Hubble Space...

The laws of star formation challenged

An international team led by researchers at CNRS, Université Grenoble Alpes and the French Alternative Energies and Atomic...

Prediction: More gas-giants will be found orbiting Sun-like stars

New planetary formation models from Carnegie's Alan Boss indicate that there may be an undiscovered population of gas...

Ancient light illuminates matter that fuels galaxy formation

Using light from the Big Bang, an international team led by Cornell University and the U.S. Department of...

WASP-18b has smothering stratosphere without water

A NASA-led team has found evidence that the oversized planet WASP-18b is wrapped in a smothering stratosphere loaded...

Alien megastructure not the cause of dimming of the ‘most mysterious star in the universe’

A team of more than 200 researchers, including Penn State Department of Astronomy and Astrophysics Assistant Professor Jason...

Stellar egg hunt with ALMA

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) took a census of stellar eggs in the constellation Taurus...

Life on Mars?

According to NASA, scientists are in agreement that there is no life on Mars. However, they continue to...