Mr. Ferri, the destination of the spacecraft Rosetta is a comet, 67P/Churyumov-Gerasimenko. On the way two asteroids will be visited as well. What is the difference between those objects and what is Rosetta looking for?

Ferri: At the comet we are primarily looking for material that gives us information about the beginnings of the solar system. Comets, at least that is what we believe, are still in their original state just like through the forming process of the solar system. The reason is that they were pushed to the border of the solar system right in the beginning and stayed there. It is very cold out there, so the matter was frozen and conserved in its original state.

And what is the case with the asteroids?

Ferri: Asteroids are different. They changed in different stages of the solar system. Some stayed inside, in the main asteroid belt. Maybe they are remains of an old planet or parts, which – for whatever reason- missed forming a planet. So they show us a different stage of our solar system’s history.

The Classification of the asteroids only depends on the materials on the surface. What is on the inside of the minor planets?

Ferri: That is probably the most important question in the context of asteroids, but it is very hard to answer. You see, from earth we can only see the surface and measure the spectrum. The inner composition is much harder to detect. For that purpose we need to actually land on the asteroid or at least instruments, which can look inside the planet so to speak. As long as that is impossible we can only draw our conclusions from the data that we have.

So what conclusions do you draw?

Ferri: In the case of Steins we see pictures with a crater on them, which is almost as big as the whole asteroid itself. The impact that caused this crater must have had an enormous amount of energy. If Steins, like some theories about planetoids suspect, was just a rubble pile, then it would have practically exploded on impact. That the asteroid survived the impact can mean that it is strong and solid on the inside.

The asteroids could be leftovers from an unknown, later destroyed planet; or they could be raw material, which for unknown reasons never clumped and formed a bigger object. Can we expect that Rosetta‘s research can support one of these theories?

Ferri: The fly-bys will defiantly help to reinforce one of the theories. However I doubt that the two fly bys are enough to develop a complete theory. The research about these small objects is just at the beginning.

Carolin Konermann is a journalist in Cologne, Germany

Mr. Ferri, the destination of the spacecraft Rosetta is a comet, 67P/Churyumov-Gerasimenko. On the way two asteroids will be visited as well. What is the difference between those objects and what is Rosetta looking for?

Ferri: At the comet we are primarily looking for material that gives us information about the beginnings of the solar system. Comets, at least that is what we believe, are still in their original state just like through the forming process of the solar system. The reason is that they were pushed to the border of the solar system right in the beginning and stayed there. It is very cold out there, so the matter was frozen and conserved in its original state.

And what is the case with the asteroids?

Ferri: Asteroids are different. They changed in different stages of the solar system. Some stayed inside, in the main asteroid belt. Maybe they are remains of an old planet or parts, which – for whatever reason- missed forming a planet. So they show us a different stage of our solar system’s history.

The Classification of the asteroids only depends on the materials on the surface. What is on the inside of the minor planets?

Ferri: That is probably the most important question in the context of asteroids, but it is very hard to answer. You see, from earth we can only see the surface and measure the spectrum. The inner composition is much harder to detect. For that purpose we need to actually land on the asteroid or at least instruments, which can look inside the planet so to speak. As long as that is impossible we can only draw our conclusions from the data that we have.

So what conclusions do you draw?

Ferri: In the case of Steins we see pictures with a crater on them, which is almost as big as the whole asteroid itself. The impact that caused this crater must have had an enormous amount of energy. If Steins, like some theories about planetoids suspect, was just a rubble pile, then it would have practically exploded on impact. That the asteroid survived the impact can mean that it is strong and solid on the inside.

The asteroids could be leftovers from an unknown, later destroyed planet; or they could be raw material, which for unknown reasons never clumped and formed a bigger object. Can we expect that Rosetta‘s research can support one of these theories?

Ferri: The fly-bys will defiantly help to reinforce one of the theories. However I doubt that the two fly bys are enough to develop a complete theory. The research about these small objects is just at the beginning.

Carolin Konermann is a journalist in Cologne, Germany