Scientists have long considered 67P/Churyumov-Gerasimenko, or Chury for short, the comet studied by ESA’s Rosetta, to be a relic of the early days of the Solar System. But researchers now think that its famous duck shape is actually much younger.
In a paper published in Astronomy & Astrophysics, Martin Jutzi and Willy Benz from the University of Bern, Switzerland, in collaboration with colleagues, created a simulation to work out the comet’s history, and the findings suggest that the bilobed shaped might have formed within the last 1 billion years.
“It is unlikely that a body like Chury has survived for such a long time without damage – our computer simulations show this,” said Jutzi in a statement.
The simulation is backed by other studies that looked at the origin of this comet. Researchers from the University of Padua, Italy, argued last year that Chury was indeed formed by two cometary nuclei that fused into one after a low-velocity impact.
More recent studies point out that the formation of bilobed comets like Chury might happen often. All the objects in the Solar System have experienced collisions throughout the 4.5 billion years of its history. 67P’s duck shape is too fragile to withstand all those impacts.
“We have found that this structure can be destroyed easily, even with low energy collisions,” said Jutzi.
“Chury’s present shape is the result of the last major impact which probably occurred within the last billion years.”
Jutzi and Benz also published another paper, also in Astronomy & Astrophysics, focusing on the composition of the comet. Comets are studied because the material they are made of is unchanged since the formation of the Solar System.
The fact that their shape changes might be problematic, but the research has shown that the impacts that have shaped Chury have been low energy enough to maintain its original composition.
"So far, it has been assumed that comets are original building blocks – similar to Lego," said Benz. "Our work shows that the Lego blocks no longer have their original form, but the plastic that they consist of is still the same as in the beginning."