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The mystery surrounding the extinction of dinosaurs gained a new “twist” this week, when scientists announced that it might have been a comet what drove those ancient beasts to extinction, rather than an asteroid as previously thought.

Scientists do still believe that the 122-mile Chicxulub crater in Mexico was made by the impact that the fast-tracked the extinction of dinosaurs and as much as 70% of Earth’s living organisms. But, as a new study presented this week at the 44th Lunar and Planetary Science Conference in The Woodlands, Texas, points out, the crater was probably dug by a faster, smaller object than what everyone had previously in mind.

Now, what make scientists think that the crater was caused by an impact, in the first place? Well, evidences are everywhere. Literally. The earth is covered with a layer of sediments containing high levels of the element iridium – called the Cretaceous-Paleogene(K--Pg) boundary – which does not occur naturally on Earth.

In all, the new study agrees with a great deal of what was already known about the disaster that killed dinosaurs. One of the exceptions being the value of iridium. The study points that there’s a mismatch between the often-cited values of iridium when compared with level of osmium, another element delivered by the impact.

Another revelation from the study was that the calculations hints to a less dramatic impact; the outer space rock generated less debris than thought, which derives from the fact that it was smaller. And because the rock might have been actually smaller, it follows that it might have been travelling faster to make up for the damage it caused.

"How do we get something that has enough energy to generate that size of crater, but has much less rocky material? That brings us to comets," study author Jason Moore, a paleoecologist at Dartmouth College in New Hampshire, said during an interview to BBC News.