Why is Mars smaller than Earth?

Have you ever wondered why Mars is smaller than Mother Earth? A new study has found that the red planet developed in as little as two to four million years after...

A new study has found that Mars developed in as little as two to four million years after the birth of the solar system, far more quickly than Earth.

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The red planet's rapid formation helps explain why it is so small, said the study's co-authors, Nicolas Dauphas at the University of Chicago and Ali Pourmand at the University of Miami.

Mars probably is not a terrestrial planet like Earth, which grew to its full size over 50 to 100 million years via collisions with other small bodies in the solar system, said Dauphas, a geophysicist.

"Earth was made of embryos like Mars, but Mars is a stranded planetary embryo that never collided with other embryos to form an Earthlike planet," said Dauphas.

Dauphas and Pourmand were able to refine the age of Mars by using the radioactive decay of hafnium to tungsten in meteorites.

The research was published in this week''s issue of the journal Nature.