Mars is full of craters, signs of space rocks having slammed into the planet over its long life. The European Space Agency’s Mars Express spacecraft spotted a rare overlapping crater triplet, and it’s giving scientists insights into ancient times on the red planet.
ESA described the overlapping formation as “particularly unusual.” It’s located in Noachis Terra, a region blasted with asteroid and comet impact craters that date back to around 4 billion years ago. The largest crater of the trio stretches 28 miles (45 kilometers) across.
While the crater arrangement could be serendipitous, ESA suggests it may have started off as one impactor that broke up into three parts before reaching the surface.
“Interestingly, if the impactor did indeed fragment and break apart, this may imply that the atmosphere of Noachian Mars was far denser – and harder to penetrate – than it is now,” said ESA in statement on Thursday. “This points towards an early Mars that was far warmer and wetter than the cold, arid world we see today.”
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The craters are showing signs of age, including infill from sediments and erosion on the rims. The relatively smooth landscape around the triplet hints at the action of ice over time. “As ice just under the surface of Mars flows and melts over many millions of years, the soil becomes softer,” said ESA.
The triplet craters may be worn down from their long lives, but they are an open window into Mars’ past. That likely history of warmth and water is why. These craters are three more reasons to keep exploring.