Impact erosion helped Earth achieve a habitable climate; Venus wasn’t so lucky

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Venus, often considered Earth’s sister, is very similar to our planet in terms of its density, mass and gravity; however, it isn’t habitable and scientists may have found the reason behind the huge difference in the two planets.

Impact erosion – an event that causes crust of a planet to wear off and lost to space because of an asteroid bombardment – is believed to the reason why Earth was able to shed away its first crust rich in radioactive heat-producing elements such as uranium and potassium and Venus wasn’t.

Researchers, in a paper published in Nature Geoscience, have put forward their theory that not only helps explain the evolutionary path of Venus and Earth, but also sheds light on a landmark discovery made over a decade ago about the Earth’s composition.

Researchers with the University of British Columbia and University of California, Santa Barbara believe that because of asteroid impacts, Earth lost uranium and potassium to space and this early loss played a rather crucial role in determining the evolution of Earth’s plate tectonics, magnetic field and climate, which eventually made conditions right on the planet for life to spawn.

“The events that define the early formation and bulk composition of Earth govern, in part, the subsequent tectonic, magnetic and climatic histories of our planet, all of which have to work together to create the Earth in which we live,” said Mark Jellinek, a professor in the Department of Earth, Ocean & Atmospheric Sciences at UBC. “It’s these events that potentially differentiate Earth from other planets.”

If we look at Earth, tectonic plates shift and this causes regular overturning of Earth’s surface. This causes steady cooling of the underlying mantle, while also maintaining the planet’s strong magnetic field and stimulating volcanic activity. Erupting volcanoes release greenhouse gases from deep inside the planet and regular eruptions help to maintain the habitable climate that distinguishes Earth from all other rocky planets.

Venus on the other hand has is a climate catastrophe with a thick carbon dioxide atmosphere and surface temperatures reaching about 470 C. Venus didn’t have as much impact erosion as Earth because of which there were episodes of cooling with catastrophic swings in the intensity of volcanic activity driving dramatic and billion-year-long swings in climate.

This never actually led to cooling of the crust or the mantle as is required for life to spawn, researchers say.

Simulating their theory, researchers say that the initial conditions that governed the initial composition of a planet can have profound consequences for its evolution. It’s a very special set of circumstances that make Earth.