Why 67P/ Churyumov-Gerasimenko?

      Rosetta's space mission was to follow the asteroid 67P until the spacecraft and the asteroid rendezvous and carry a scientific study of the asteroid. But what is the point of following this specific asteroid?

      To answer that question we must consider some of the most important factors which made the ESA choose this asteroid.

      The main point that was observed was that the asteroids must be near enough so the spacecraft was able to rendezvous with them as soon as posible. At the beginning, 67P was not selected as the target, but, due to some problems with the Ariane 5 (the carrier rocket of Rosetta) the launch was postposed to the next year, so it was impossible for Rosetta to reach 46P/ Wirtanen at time. Due to this, 67P was designated as the main target.

This decision was made because 67P was know for having water vapor, so the objective of the space mission Rosetta was stablished as analyzing that water vapor in order to aloud us to study the difference of "extraterrestrial" water and earth´s water.

Comet 67P on 7 August