with findings by the Dawn spacecraft, which visited the asteroid Vesta from 2011 to 2012 for imaging, and samples from HED meteorites (collected on Earth until then), which were compared to data gathered by Dawn. These meteorites could then be identified as material ejected from the large impact crater Rheasilvia on Vesta. This allowed deducing the composition of the crust, mantle and core of Vesta. Similarly, some differences in the composition of asteroids (and, to a lesser extent, different compositions of comets) can be discerned by imaging alone. However, for a more precise inventory of the material on these different bodies, more samples will be collected and returned in the future, to match their compositions with the data gathered through telescopes and astronomical spectroscopy. One further focus of such investigation—besides the basic composition and geologic history of the various Solar System bodies—is the presence of the building blocks of life on comets, asteroids, Mars or the moons of the gas giants. Several sample-return missions to asteroids and comets are currently in the works. More samples from asteroids and comets will help determine whether life formed in space and was carried to Earth by meteorites. Another question under investigation is whether extraterrestrial life formed on other Solar System bodies like Mars or on the moons of the gas giants, and whether life might even exist there. The result of NASA's last "Decadal Survey" was to prioritize a Mars sample-return mission, as Mars has a special importance: it is comparatively "nearby", might have harbored life in the past, and might even continue to sustain life. Jupiter's moon Europa is another important focus in the search for life in the Solar System. However, due to the distance and other constraints, Europa might not be the target of a sample-return mission in the foreseeable future. Planetary protection Planetary protection aims to prevent biological contamination of both the target celestial body and the Earth in the case of sample-return missions. A sample return from Mars or other location with the potential to host life is a category V mission under COSPAR, which directs to the containment of any unsterilized sample returned to Earth. This is because it is unknown what the effects such hypothetical life would be on humans or the biosphere of Earth. For this reason, Carl Sagan and Joshua Lederberg argued in the 1970s that we should do sample-return missions classified as category