![comet vs asteroid comet vs asteroid](https://cdn.arstechnica.net/wp-content/uploads/2010/10/fake_comet_asteroid.jpg)
He said comets are largely made of ice, and it would have to be significant in size to survive entering the Earth's atmosphere. The final question centres on whether the object was an asteroid or a comet, he said. He said it's already known when the impact happened, and where it hit. Petrus, who has always had an interest in space, said he approached his research, which included looking at trace metals found in the rock around Sudbury, with three questions: What was the impact? What was the area of Earth that it hit? When did that happen? Today, the Sudbury Basin produces hundreds of tonnes of nickel and copper every year and has the biggest concentration of mines in the world. The wealth of minerals was discovered by accident when railway engineers were constructing the Canadian Pacific Railway in 1885. A subsequent shock wave shattered the surrounding rocks, riddling them with fissures and faults that filled up with precious minerals from the melted rock below. When it slammed into the earth, it punched a hole in the Earth’s crust, allowing the mantle below to well up and fill the basin with a thick sheet of melted rock. The fiery object that struck near Sudbury, 1.8 billion years ago, formed a deep hole that can be seen from space. It's one of the largest and one of the oldest."
![comet vs asteroid comet vs asteroid](http://files.differencebetween.com/wp-content/uploads/2014/05/Asteroid-Belt.png)
"Sudbury is kind of unique in terms of meteorite impact. "Impacts provide … a way to connect space earth by looking at the interaction of things that were in space that have come and created a massive crater on earth," he said. (Jenifer Norwell/CBC)PhD candidate Joe Petrus's r ecent research looks at what exactly came crashing down from space to form the massive crater. Joe Petrus is a researcher at Laurentian University in Sudbury.