We might be wrong about how Mars formed, scientists have said.

The Red Planet may have taken much longer to form, and done so in an unexpectedly violent way, according to new research.

It is hard to know how Mars formed, and how much that was dictated by collisions in the early solar system, because the surface has been wiped of evidence over the billions of year that have come between.

But by studying rock on Earth that made its way here from Mars, researchers think they have pulled together some of the story of the distant planet's early history..

It suggests that the planet might have formed over a longer time than previously thought, and been bombarded with small protoplanets as its early history was taking shape.

Nasa's groundbreaking decade of space exploration: In pictures Show all 10 1 /10 Nasa's groundbreaking decade of space exploration: In pictures Nasa's groundbreaking decade of space exploration: In pictures Mystic Mountain, a pillar of gas and dust standing at three-light-years tall, bursting with jets of gas from fledgling stars buried within, was captured by Nasa's Hubble Space Telescope in February 2010 Nasa/ESA/STScI Nasa's groundbreaking decade of space exploration: In pictures The first ever selfie taken on an alien planet, captured by Nasa's Curiosity Rover in the early days of its mission to explore Mars in 2012 Nasa/JPL-Caltech/MSSS Nasa's groundbreaking decade of space exploration: In pictures Death of a star: This image from Nasa's Chandra X-ray telescope shows the supernova of Tycho, a star in our Milky Way galaxy Nasa Nasa's groundbreaking decade of space exploration: In pictures Arrokoth, the most distant object ever explored, pictured here on 1 January 2019 by a camera on Nasa's New Horizons spaceraft at a distance of 4.1 billion miles from Earth Getty Nasa's groundbreaking decade of space exploration: In pictures An image of the Large Magellanic Cloud galaxy seen in infrared light by the Herschel Space Observatory in January 2012. Regions of space such as this are where new stars are born from a mixture of elements and cosmic dust Nasa Nasa's groundbreaking decade of space exploration: In pictures The first ever image of a black hole, captured by the Event Horizon telescope, as part of a global collaboration involving Nasa, and released on 10 April 2019. The image reveals the black hole at the centre of Messier 87, a massive galaxy in the nearby Virgo galaxy cluster. This black hole resides about 54 million light-years from Earth Getty Nasa's groundbreaking decade of space exploration: In pictures Pluto, as pictured by Nasa's New Horizons spacecraft as it flew over the dwarf planet for the first time ever in July 2015 Nasa/APL/SwRI Nasa's groundbreaking decade of space exploration: In pictures A coronal mass ejection as seen by the Chandra Observatory in 2019. This is the first time that Chandra has detected this phenomenon from a star other than the Sun Nasa Nasa's groundbreaking decade of space exploration: In pictures Dark, narrow, 100 meter-long streaks running downhill on the surface Mars were believed to be evidence of contemporary flowing water. It has since been suggested that they may instead be formed by flowing sand Nasa/JPL/University of Arizona Nasa's groundbreaking decade of space exploration: In pictures Morning Aurora: Nasa astronaut Scott Kelly captured this photograph of the green lights of the aurora from the International Space Station in October 2015 Nasa/Scott Kelly

Researchers have previously looked at elements found in meteorites that came down from Mars and concluded that Mars would have grown rapidly after the first 2-4 million years of the Solar System's existence. But the new study suggests that it would have been smashed with collisions during that earlier history, and the formation might have taken as long as 20 million years.

Some 61,000 meteorites have been found on Earth, and about 200 of them are thought to have come here Mars. Those that have been discovered were probably thrown off Mars during collisions in its more recent history.

Looking through those rocks, scientists found elements such as tungsten and platinum, which tend to cling to iron. Such elements tend to find their way from the mantle towards the edges of the planet and into the core at its centre as the planet forms.

The discovery of those elements in the rock suggests that Mars was hit by what scientists call planetesimals – small objects not big enough to be planets – after its core had been created.

Researchers can look at the isotopes of those particular elements and understand at what time planet formation happened.

"We knew Mars received elements such as platinum and gold from early, large collisions. To investigate this process, we performed smoothed-particle hydrodynamics impact simulations," said Dr. Simone Marchi, lead author of the new paper, from the Southwest Research Institute.

"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."

The pieces of Mars that came down to Earth probably came from a relatively limited number of places on the Red Planet. Researchers now hope that future Mars missions can pick up pieces of the planet and bring them back down to Earth, giving a better understanding of the makeup of elements in Martian rocks and more detail on how the planet formed.