Mars might have formed over longer time than previously thought

A study in Science Advances suggests that early large-scale collisions on Mars may have led to an underestimation of the planet's age. The Southwest Research Institute found that the tungsten content in Martian meteorites is highly varied, indicating that Mars formed rapidly in 2 to 4 million years. However, new models propose that Mars's formation involved significant collisions, creating a marbled mantle structure. This could mean Mars took 20 million years to fully form.

What does the heterogeneous marbled structure of Mars imply about its formation?

According to the researchers, how long did it take for Mars to become fully formed?