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#The moon has a NEON atmosphere: Ladee spacecraft confirms presence of the gas for the first time The presence of neon in the moon atmosphere has been a subject of speculation for decades. Now, for the first time, scientists have confirmed the gas is not only present, but abundant on the moon. The discovery was made by analysing data sent back from Nasa Lunar Atmosphere and Dust environment Explorer, known as Ladee. he presence of neon in the exosphere of the moon has been a subject of speculation since the Apollo missions, but no credible detections were made, said Mehdi Benna of Nasa's Goddard Space flight Centre in Greenbelt, Maryland and the University of Maryland, Baltimore County. e were pleased very to not only finally confirm its presence, but to show that it is relatively abundant. Readings from the spacecraft Neutral Mass spectrometer (NMS) instrument published in the journal Geophysical Research Letters, show there is not enough neon to make the moon glow, but its thin atmophere is made up of mostly, helium, argon and neon. While the gas is used in electric signs On earth, there is not enough neon to make the moon glow visibly, because the moon's atmosphere is about 100 trillion times less dense that the Earth at sea level. The moon atmosphere is referred technically to as an exosphere because it so thin. Exospheres are the most common type of atmosphere in our solar system, so scientists are keen to learn more about them. t's critical to learn about the lunar exosphere before sustained human exploration substantially alters it, Dr Benna said. Since the moon's atmosphere is so thin, rocket exhaust from spacecraft could easily change its composition. Most of the moon's exosphere comes from the solar wind, which is a thin stream of electrically conducting gas blown from the surface of the sun into space at around a million miles per hour. Most of the solar wind is hydrogen and helium but it contains many other elements in small quantities, including neon. All these elements impact the moon, but only helium, neon, and argon are volatile enough to be returned back to space. The rest of the elements will stick indefinitely to the moon surface. Ladee NMS instrument confirmed the moon exosphere is made up of mostly helium, argon, and neon. The make-up of the mixture changes depending on the time of day, with argon peaking at sunrise, neon at 4am and helium at 1am. The instrument conducted measurements of the gases for seven months, which allowed the team to understand how they are supplied to the exosphere, and how they are lost ultimately. While most of the lunar exosphere comes from the solar wind, the readings showed that some gas comes from lunar rocks. For example, Argon-40 comes from the decay of naturally occurring radioactive potassium-40, found in the rocks of all the terrestrial planets as a leftover from their formation. e were surprised also to find that argon-40 creates a local bulge above an unusual part of the moon's surface, the region containing Mare Imbrium and Oceanus Procellarum, Dr Benna said. The scientists found that argon-40 creates a local bulge above an unusual part of the moon's surface the region containing Mare Imbrium (shown)+ 6 The scientists found that argon-40 creates a local bulge above an unusual part of the moon's surface, the region containing Mare Imbrium (shown) Although the reason for this local enhancement is understood not yet, ne could not help to notice that this region happens to be the place where potassium-40 is most abundant on the surface. o there may be a connection between the atmospheric argon, the surface potassium and deep interior sources, he explained. The team also noted that a second surprising behaviour of argon that the overall amount in the lunar exosphere was not constant over time. In fact it increased and decreased by about 25 per cent during the course of the Ladee mission. Dr Benna believes this transient source of argon may be the result of enhanced outgassing-the release of a gas that was dissolved, trapped, frozen or absorbed in some material-from the surface that is triggered by tidal stress on the moon. Ladee readings also revealed an unexpected source of some of the helium in the lunar exosphere. bout 20 percent of the helium is coming from the moon itself, most likely as the result from the decay of radioactive thorium and uranium also found in lunar rocks, said Dr Benna. It being produced at a rate equivalent to about seven litres per second at standard atmospheric pressure. he data collected by the NMS addresses the longstanding questions related to the sources and sinks of exospheric helium and argon that have remained unanswered for four decadesdr Benna said. hese discoveries highlight the limitations of current exospheric models and the need for more sophisticated ones in the future. Ladee launched in September 2013 and began gathering science data two months later. The spacecraft entered its science orbit around the moon's equator in Mid-november and its mission was extended. However, the craft lacked fuel to maintain a long-term lunar orbit or continue science operations and was sent intentionally into the lunar surface, impacting the moon on April 17, 2014

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