Mars sample-return mission gained from the "Hayabusa 2" and SLIM missions. Of the two moons, Phobos's orbit is closer to Mars and its surface may have adhered particles blasted from the red planet; thus the Phobos samples collected by MMX may contain material originating from Mars itself. Japan has also shown interest in participating in an international Mars sample-return mission. Since it is currently unknown whether life forms exist on Mars, the mission could potentially transfer viable organisms resulting in back contamination—the introduction of extraterrestrial organisms into Earth's biosphere. The scientific consensus is that the potential for large-scale effects, either through pathogenesis or
Definition of planet to 400 astronomical units from the star. A Mars-mass body at the orbit of Pluto clears its orbit. This metric, which leaves Pluto as a dwarf planet, applies to both the Solar System and to extrasolar systems. Some opponents of the definition have claimed that "clearing the neighbourhood" is an ambiguous concept. Mark Sykes, director of the Planetary Science Institute in Tucson, Arizona, and organiser of the petition, expressed this opinion to National Public Radio. He believes that the definition does not categorise a planet by composition or formation, but, effectively, by its location. He believes that a Mars-sized or