Boom! Bam! Boom! How to make a triple crater on Mars | Space

The European Space Agency (ESA) released the above image late last month (October 29, 2020), which shows a triple crater in a particularly ancient part of Mars’ southern hemisphere. This region on Mars – known as Noachis Terra – was heavily bombed early in our solar system’s history, some 4 billion years ago, when debris left over from the birth of the planets flew free. Do you see the rounded edges of these craters? It is a sign that they are old and worn by time. How would such a crater triplet be formed? There are several possibilities.

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One possible explanation, ESA said – and thought to be the most likely explanation – is that incoming debris (what we might now call an asteroid or comet) broke into three pieces before hitting the ground, forming the trio of craters on impact. But ESA added:

Not all “ multiple simulation devices ” leave such clear-cut features in their wake, but many show elongated depressions, non-circular cavities lying side by side or only partially overlapping basins.

Another explanation could be a coincidence: at different times, three separate impactors could have hit the surface of Mars in this position, creating a net overlap of craters completely by accident.

Interestingly, if the impactor has indeed fragmented and broken, this could imply that the atmosphere of [Mars in its Noachian era, 3.7 to 4.1 billion years ago] it was much denser – and harder to penetrate – than it is now.

This indicates a primeval Mars that was much hotter and wetter than the cold and arid world we see today. Observations from numerous missions support this view and return evidence that water once flowed through the red planet in large quantities, revealing features such as old river valley networks and large lake basins thought to have formed in the Noachian period.

Like many of the ancient and eroded craters in the southern highlands of Mars, these three craters have flattened edges, shallow floors, and have been filled with sediment in the 4 billion years since their formation. There is also evidence of ice here: the smaller crater has markings that are typically created when ice and debris creep onto a surface, similar to how mixed rock and ice glaciers or debris-covered glaciers move in alpine regions. of the Earth.

ESA also said that – in the image above – signs of other craters can be seen, as indicated by the round patches of sunken surface in the upper right and lower left. In fact, ESA said:

… Despite the cratered nature of Noachis Terra, the environment around this triplet is surprisingly smooth for such an ancient terrain. Only a handful of small surrounding craters appear to have clear, sharply defined edges and bowls, indicating that they are relatively young and have not yet begun to seriously erode. Overall, the older craters in this area appear to have “melted” on the surface, a phenomenon which is, again, due to ice.

As the ice just below the surface of Mars flows and melts over many millions of years, the soil becomes softer. This soft, ice-rich soil subsides more quickly and fills indentations and depressions more readily, contributing to the smooth appearance of this part of Noachis Terra. This suggests that there must have been a large amount of water on Mars, at least during the Noachian period, capable of producing a glacier-like flow of ice in abundance.

Understanding the history of Mars and mapping in detail the features covering the planet’s surface is a key objective of Mars Express.

Bottom line: Late last month, the European Space Agency released an interesting image from Mars Express, showing a triple aged crater. Scientists are studying this image to learn more about the history of Mars.

Via ESA