Revealed - Formation of five giant impact scars on Mars

Image credit: NASA/Twitter

New Delhi: Scientists have revealed that the ancient surfaces of Mars, like those on the moon and Mercury, are covered with the scars of asteroid impacts.

Now, a new study funded by NASA suggests that Mars experienced ten times fewer giant impacts than some previous estimates.

Scientists Bill Bottke from the Southwest Research Institute, or SwRI, and Jeff Andrews-Hanna from the University of Arizona have been investigating the early bombardment history of Mars and the timing of giant impacts.

Mars bears the scars of five giant impacts, including the ancient giant Borealis basin (top of globe), Hellas (bottom right), and Argyre (bottom left). A NASA-funded team at SwRI discovered that Mars experienced a 400-million-year lull in impacts between the formation of Borealis and the younger basins. Credits: University of Arizona/LPL/Southwest Research Institute

The new findings indicate that the Borealis basin carved out the northern lowlands 4.5 billion years ago, followed by a lull of 400 million years during which no giant impacts occurred, culminating in a shower of impacts between 4.1 and 3.8 billion years ago during which four giant basins and countless smaller craters formed, says a release by NASA.

Borealis is the largest and most ancient giant impact basin on Mars and is nearly 6,000 miles wide, encompassing most of the northern hemisphere of the Red Planet. A smaller giant basin called Hellas is 1,200 miles wide and five miles deep.

Bottke and Andrews-Hanna collected data and ran models to support their findings that the rim of Borealis was excavated by only one later giant basin, called Isidis.

“This sets strong statistical limits on the number of giant basins that could have formed on Mars after Borealis”, said Bottke, principal investigator of the Institute for the Science of Exploring Targets, or ISET, team with NASA’s Solar System Exploration Research Virtual Institute or SSERVI.

“The number and timing of such giant impacts on early Mars has been debated, with estimates ranging from four to 30 giant basins formed in the time since Borealis. Our work shows that the lower values are more likely.”

To fully understand the implications of this bombardment, they analysed the timing of the impacts responsible for other giant basins, and compare their preservation state.

They found that the preservation state of the four youngest giant basins on Mars - Hellas, Isidis, Argyre, and the now-buried Utopia basins - are strikingly similar to the larger and older Borealis basin.

The similar preservation of both Borealis and these younger basins indicates that any basins formed during this time interval should be similarly preserved.

The research has been published in Nature Geoscience.