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 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.
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 from 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. This suggests that Mars was hit by what scientists call planetesimals — small objects not big enough to be planets.
Researchers can look at the isotopes of those particular elements and understand at what time planet formation happened.
“Based on our model, early collisions produce a heterogeneous, marble-cake-like Martian mantle. These results suggest the prevailing view of Mars formation may be biased by the limited number of meteorites available for study,” said Simone Marchi, lead author of the new paper.
The pieces of Mars that came down to Earth may have come from a limited number of places on the 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.