Mars may have taken as long as 20 million years to form, scientists now claim.

The new timescale rewrites Martian history – as it was previously thought Mars formed in as little as 2 million years.

Scientists are constantly trying to map out our solar system’s past.

One of the big questions is: how did the planets form and how long did it take?

Now experts have modeled the birth of Mars and think it happened surprisingly slowly.

Early in Martian history, the planet was likely struck by small protoplanets around 1,200 miles across.

Scientists have tried to model how the materials associated with these impacts mixed.

Around 200 meteorites than have turned up on Earth are believed to be Martian in origin.

They feature elements like tungsten and platinum, which are likely to have migrated from the mantle to its central iron core during formation.

The evidence of these elements in the Martian mantle – as seen in meteorites – is important because they show that Mars was bombarded by protoplanets after its main core formation ended.

By studying the radioactive decay of these elements, scientists can discover when the planet finished forming.

“We knew Mars received elements such as platinum and gold from early, large collisions,” said lead author Dr. Simone Marchi, of the Southwest Research Institute.

“To investigate this process, we performed smoothed-particle hydrodynamics impact simulations.

“Based on our model, early collisions produce a heterogeneous, marble-cake-like Martian mantle.

“These results suggest that the prevailing view of Mars formation may be biased by the limited number of meteorites available for study.”

Scientists previously thought that Mars grew quickly between two and four million years after the solar system formed.

But the new model suggests the real timescale is as high as 20 million years.