In its 4.6 billion year history, Mars has taken its fair share of blows from falling asteroids and collapsing comets.

Today, there are at least 43,000 impact craters larger than 5 km across the surface of the Red Planet; Some old areas were hit more than others.

And astronomers discovered in the ancient Martian highlands of Noachis Terra - a region that was severely affected nearly 4 billion years ago - a triple blow crater made of three overlapping basins.

The Venn diagram of the depressions is not as large as some of the other craters at Noachis Terra, some of which can extend nearly 140 km, but the smallest crater in the area is still 28 km wide.

It is difficult to know if the triple-impact crater was caused by one or more collisions. The researchers say the collider may have broken into 3 pieces before hitting the ground in a close formation, but other examples of this shattering approach do not show such clear definitions of the edges, nor are they precisely overlapping.

It is not uncommon to see double and triple impact craters, and we sometimes find them on the surface of Mars and even on Earth, although they do not all form the same way.

And in 2015, for example, astronomers observed a similar triple crater at Elysium Planitia near Mars' equator. At the time, the team thought it could be due to an asteroid crashing into the atmosphere, or it could be due to a smaller asteroid orbiting a larger binary pair.

And in 2017, the Mars Reconnaissance Orbiter observed an extended decline from three compact collision craters, which astronomers said may have come from three pieces flying in a nearby formation.

Some also assumed that the double craters were caused by double asteroids, consisting of two or more rocky bodies in close contact or orbiting around each other. Only about 2% of all asteroids are thought to be composed of two or more such objects, but this does not mean that they sometimes cannot collide with a planet and leave a scar.

"The other explanation may be a coincidence," said a press release about the latest triple crater from the European Space Agency. "At different points in time, there could be three separate collisions that collided with the surface of Mars at this location, resulting in a neat explosion."

Given how heavily bombed this region of Mars once was, experts say this is the most likely possibility, although not the most interesting.

On the other hand, if this wasn't due to three encounters by chance, and the probe actually broke down before hitting Mars, then this tells us something important about this planet: 4 billion years ago, the Martian atmosphere was probably more difficult to penetrate than it is now, and that means Warmth and humidity.

Similar to other craters in the area, this triple impact crater shows flat edges and shallow floors from the wear of time. Some of its signs even indicate a glacier-like flow, which may have helped soften the soil underneath, gradually filling the void as the ice melted.

Source: ScienceAlert

By:Nadeemy Haded