Mars may have formed slower than thought, scientists say
Researchers believe their findings support ‘a Mars formation timescale of up to 20 million years’.
Mars formed gradually, accumulating mass over a period of 20 million years by pulling particles into its gravitational field, scientists believe.
Researchers said their findings, based on computer simulations, contradict previous theories that the Red Planet grew more rapidly in just two to four million years after the Solar System started to form.
In the past, scientists have used Martian meteorites found on Earth to construct a timeline of the planet’s formation.
But due to a limited number of meteorites available for research, the authors of the new study, published in Science Advances, said that the “prevailing view of Mars’ formation may be biased”.
There are around 200 Martian meteorites on Earth, thought to have been ejected from the Red Planet during collisions with large asteroids.
Dr Simone Marchi, of the Southwest Research Institute, in Texas, US, and lead author of the study, said: “To fully understand Mars, we need to understand the role the earliest and most energetic collisions played in its evolution and composition.”
Samples from the Martian meteorites show large variations in elements such as tungsten, platinum and gold.
Scientists said the evidence of these variants, or isotopes, of the elements are important because they indicate Mars was bombarded by asteroids “sometime after its primary core formation ended”.
They believe these elements entered the planet’s mantle, the layer surrounding the core, and sank into its central core after the collisions.
Dr Marchi said: “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.
“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.”
It has previously been argued that Mars grew rapidly within about two to four million years, based on analysis of tungsten isotopes in the Martian meteorites.
But recent computer simulations suggest large, early asteroid collisions could have changed the tungsten isotopic balance, which, according to the study authors, could support “a Mars formation timescale of up to 20 million years”.
The scientists said that knowing more about how and when Mars was formed can help unlock other mysteries, such as the planet’s temperature and atmosphere during its evolution.
