The moment has come. After a two-year journey and almost two more of observations in orbit, the OSIRIS-REx spacecraft, a device the size of a minibus, will land for about ten seconds on the rugged surface of Bennu, an asteroid made of debris and size of the Empire State. The encounter will take place at a distance of more than 300 million kilometers and will require the spacecraft to land in an area comparable to five parking spaces, while the asteroid rotates and solar radiation changes its trajectory. An automatic system will guide it to the surface, avoiding gigantic blocks the size of houses, and a robotic arm will touch the asteroid for several seconds, injecting pressurized gas to lift between 60 and 2,000 grams of samples from the asteroid. These samples are a relic of the formation of the solar system, and an important testimony of the formation of organic compounds and the role of water in the beginnings of our planetary system. In addition, Bennu is the second most dangerous asteroid for Earth, and scientists want to know more about its composition and trajectory.
