The first ESA instrument to land on the Moon has detected the presence of negative ions on the lunar surface produced by interactions with the solar wind. The European team working with the NILS (Negative Ions at the Lunar Surface) instrument confirmed the success of this scientific mission that flew to the far side of the Moon aboard the Chinese Chang’e-6 spacecraft. This robotic mission arrived at the Moon on June 2 and left on the 4th with samples bound for Earth. The discovery of a new plasma component on the surface of the Moon opens a new window for space physics and for human and robotic missions in an era of renewed lunar exploration The first negative ion detector on the Moon worked intermittently to collect more than three hours of data, three times more than what the scientific teams needed for the success of the mission. This was the first time that ESA produced scientific data on the lunar surface. The solar wind is a constant flow of radiation and particles from the Sun. The Earth’s magnetic field acts as a shield. On the other hand, the Moon has no magnetic field and its atmosphere, called the exosphere, is very tenuous. When the solar wind hits the Moon, the surface reacts and lifts up secondary particles. These particles can be positively or negatively charged, or have no charge at all. Although positively charged particles had been measured from orbit before, measuring negative particles was a challenge. Negative ions have a short life and cannot reach orbit. Therefore, European scientists needed to operate their instrument near the lunar surface, an unprecedented mission for a particle detector. “These observations on the Moon will help us better understand the surface environment and act as a reference point for exploring negative ion populations on other airless bodies in the Solar System, from planets to asteroids and other moons,” explains Martin. Wieser, principal investigator of the NILS at the IRF.
