Researchers have concluded that the Moon’s spin axis was shifted approximately 5 degrees around 3 billion years old, according to NASA-funded research. After analyzing ancient lunar ice distribution at two poles, the researchers came up with this conclusion. This is evidence that water was delivered to the Solar System in the early days. The scientists stated that it is quite possible, as they explained in Nature, citing below, that the “man on the moon” was different three billion years ago. The polar hydrogen map shows the Moon’s north hemisphere and the position of its old and current north pole. The lighter areas have higher hydrogen concentrations, while the darker ones are lower. The image below shows how the South Pole has changed. (Image: nasa.gov. Credits to James Keane and Richard Miller. Man in the Moon has changed Matthew Siegler is a Planetary Science Institute employee in Tucson, Arizona. He said that the same face of the Moon does not always point towards Earth. The axis moved and so did the face’man on the moon’. Water ice may exist in permanent shadows of our Moon. Moon ice can evaporate and be lost into space if it is subjected to direct sunlight. Researchers have shown that sunlight was able to penetrate areas of Moon ice that were previously darkened by a change in the Moon’s spin direction billions of year ago. Similar to the previous image, the Moon’s South Pole moved in an opposite direction. (Image: nasa.gov. Credits to James Keane and Richard Miller. The surviving ice is a ‘painting’ of the path. Scientists discovered that the path the axis was shifting along, which was what the scientists called a ‘painting’. The scientists compared their observed path to models which predicted where the stability of the ice might be maintained, and concluded that the Moon’s orbit had changed by approximately 5 degrees. This is the first evidence to show that the Moon experienced such an abrupt orientation shift. This also indicates that the Moon’s most recent polar ice may be billions of year old. Dr. Yvonne Pendleton (director of NASA’s Solar System Exploration Research Virtual Institute), was co-author. She said that the new findings offer a fascinating view into the past dynamic of the Moon. “It is amazing to see the results from several missions pointing towards these insights.” To make a case that the Moon has changed its orientation, the authors analyzed data from a variety of NASA missions including: the Gravity Recovery and Internal Laboratory (GRAIL), Lunar Crater and Observation Sensing Satellite LCROSS, Lunar Prospector (LRO) and Lunar Crater and Observation Sensing Satellite LCROSS. Cross-section of the Moon showing the antipodal nature lunar polar volatiles and their trace to an ancient spin pole. Reorientation of that old spin pole (red Arrow) to the current spin pole was caused by evolution and formation of the Procellarum, a nearside region of the Moon with high radiogenic heat-producing elements (green), heat flow and ancient volcano activity. (Image: nasa.gov. Credit to James Tuttle Keane. Topography was taken from LOLA (Lunar Orbiter Laser Altimeter), and thermal data were collected by the Diviner Lunar Radiometer. These measurements helped in the interpretation Lunar Prospector neutrons that supports the polar wander hypothesis. The movements of Polar Ice were opposite. Dr. Siegler observed that each Moon’s pole’s ice distribution was more similar than they thought. Richard Miller from the University of Alabama in Huntsville was a co-author of Dr. Siegler’s discovery that ice concentrations moved from one pole to another at exactly opposite distances. It is possible that the spin axis was tilted differently to what we now see. The Moon tilt shift means some ancient ice is now gone because it has been exposed to the sun. The areas which remain between the new and old orientations in permanent shadow retain their ice and indicate what happened. The Procellarum area of the crust is shown in a 3D section of the moon. This region was probably responsible for tilting the moon’s orbit. (Image: nasa.gov. Credit to James Keane. A significant shift in the mass distribution can cause a planet or moon to move on their axis. James Keane from the University of Arizona, Tucson was the co-author and modeled the effects of changes on the interior of the Moon’s spin and tilt. The axis shifting was triggered by Procellarum. He discovered that only the Procellarum area on the Moon’s nearest side could replicate the direction of the axis change indicated by the ice distributions close to the poles. The Procellarum area contains enough radioactive material to heat a portion of the lunar mantle. This caused a significant density shift that allowed the Moon to be reoriented. The heated mantle material was melted, and some of it rose to the surface. These dark patches are what we now call mare. These mare patches are what give the Man on the Moon, his face. Dr. Siegler stated that these mare patches give the so-called Man on the Moon his ‘face. Nature. 23 DOI: 10.1038/nature17166. Video – Moon Lunar Polar Walk This video was produced by James Keane and shows how the Moon veered off of its original axis around 3 billion years ago.
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