Free Astronomy Magazine November-December 2015

NOVEMBER-DECEMBER 2015 25 ASTRONAUTICS teroids using E SA’s Rosetta mission, with the adven- turesome Philae landing on the com- et 67P/Churyumov-Gerasimenko, has confirmed that the exploration of the sur- faces of small solar system bodies, namely asteroids and cometary nuclei, cannot be undertaken with the same technologies and methods used for planets and their major moons. If landing and operating small self-propelled rovers and stationary A n artist’s de- piction of a Hedgehog explor- ing Phobos, a sat- ellite of Mars. Such activity would be impos- sible for a tradi- tional rover. [NASA/JPL-Cal- tech/Stanford] probes on these objects is relatively easy, for bodies of a few kilometres or a few tens of kilometres across things are much more complicated. The reason for this is the very low gravitational force, which does not guarantee a safe and steady land- ing, or the possibility to move around on wheels. This is due both to the ruggedness of the asteroidal and cometary surfaces, and because any wheeled vehicle, in a mi-