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In a good bit of lateral thinking, the astronomers from the US and the Czech Republic traced the orbit of an asteroid called 298 Baptisma backward. This is a large asteroid, which shares an orbital path with some “smaller rocks”, as the Sydney Morning Herald article elegantly puts it. A bit of analysis showed that the bits fit together. The original asteroid was estimated to be 170 km wide.

If you play pool, this'll get you thinking the next time you break. According to this theory, another asteroid, about 60km wide, hit Baptisma, about 160 million years ago, fragmenting it. This sent pieces of the asteroid into the inner Solar System, and eventually a 10km piece strayed into Earth’s path 65 million years ago, hitting the Yucatan Peninsula, and leaving a massive scar offshore. Other pieces hit Venus, Mars, and the Moon, creating massive craters.

According to the theory, the impact was the equivalent of a nuclear war. It started a firestorm which covered the Earth in the KT Layer, a boundary of iridium, a metal common in asteroids and meteors, between the Cretaceous and the following geological era. It also raised enough dust to block out the sunlight, which wiped out vegetation and doomed the animals which lived on it.

Paleontologists have been debating for a while whether this was actually what caused the dinosaurs’ extinction, but there’s no doubt this may well have been the final straw for them. They were in decline, and late Cretaceous eggs show a lack of calcium, indicating diet issues. There are at least a couple of claims that dinosaur fossils have been found on the modern side of the KT Layer, but definitive proof is lacking.

One way or another, this is a great bit of astronomy. Backtracking asteroids could lead to some useful information about the structure of the early Solar System. It might even tell us what happened to Mars. A planet covered in micro-fine dust and pulverized rocks, which evidence is starting to tell us was once covered in water, needs an explanation.