Why Earth became habitable and not Venus?

London, July 22 (IANS) Information about the improbable evolutionary path that enabled Earth and not Venus to sustain life has been found, shows research.

Venus is the most similar planet to Earth in terms of size, mass, density, gravity and composition in our solar system.

While Earth has had a stable and habitable climate over geological time, Venus is in a climate catastrophe with a thick carbon dioxide atmosphere and very high surface temperatures.

According to researchers, Earth’s first crust, which was rich in radioactive heat-producing elements such as uranium and potassium, was torn from the planet and lost to space when asteroids bombarded the planet early in its history.

This phenomenon, known as impact erosion, helps explain a landmark discovery made over a decade ago about the Earth’s composition.

“The early loss of these two elements ultimately determined the evolution of Earth’s plate tectonics, magnetic field and climate,” said the team from University of British Columbia (UBC) and University of California-Santa Barbara.

“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, professor at UBC.

It is these events that potentially differentiate Earth from other planets.

On Earth, shifting tectonic plates cause regular overturning of Earth’s surface, which steadily cools the underlying mantle, maintains the planet’s strong magnetic field and stimulates 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.

“Earth could have easily ended up like present day Venus. A key difference that can tip the balance, however, may be differing extents of impact erosion,” added Matt Jackson, associate professor at University of California.

With less impact erosion, Venus would cool episodically with catastrophic swings in the intensity of volcanic activity driving dramatic and billion-year-long swings in climate, said the study that appeared in the journal Nature Geoscience.

“There are some very special set of circumstances that make Earth,” the authors said.

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