Space Mission Brings New Details to Light
An international team of scientists discovered numerous and previously unknown thrust faults on the moon - that is, places where sections of the moon's crust jut out over another. After analysing thousands of new, high-resolution pictures taken by the "Lunar Reconnaissance Orbiter Camera", the researchers found indications of a global distribution of thrust faults for the first time ever. They report on these results in the current issue of "Science" magazine. Prof. Dr. Harald Hiesinger and Dr. Carolyn van der Bogert of the Institute of Planetology of Westfälische Wilhelms-Universität Münster were the only Europeans to be involved in the discovery.
"The new image data have a spatial resolution of some 0.5 metres and cover large areas of the moon. It was thus possible to spot thrust faults even in far northern and southern latitudes", says Carolyn van der Bogert. Harald Hiesinger adds: "The Apollo Program of the US-American space agency NASA actually did provide images with a similarly high resolution. Regarding coverage, however, the pictures were confined to areas close to the moon's equator. Because of the larger coverage, thrust fault formation models can now be tested considerably better."
One of these models, for example, assumes that formation is related to tidal forces. In such a case, a concentration of thrust faults would be expected on the side facing the earth and on the far side of the moon. According to the scientists, the distribution of the thrust faults detected now is incompatible with this model. "We are currently favouring a model according to which the moon altogether has shrunk by 0.01 per cent - which is equivalent to 100 metres in terms of the radius - due to the overall cooling and that this is the reason why crust sections are now jutting out over another in some places", says Harald Hiesinger. It is possible to observe this phenomenon on the moon because in contrast to the earth, it is a "single-plate body" with a thick outer rigid rock layer, the so-called lithosphere. "There are many plates on the earth, which move in relation to one another, form anew and also get destroyed. Because of the earth's plate tectonics, it is impossible to study the contraction of the whole planet", says Carolyn van der Bogert. First determinations of age of the moon's thrust faults imply that the formation of these structures has taken place over the past one billion years, thus being a relatively young phenomenon from the perspective of planetologists.
Under the direction of Dr. Tom Watters, of the "Smithsonian Institute" in Washington, and of Dr. Mark Robinson, of the "Arizona State University", USA, the Münster research team will continue to analyse the image data of the "Lunar Reconnaissance Orbiter Camera" and systematically search for thrust faults. "It will thus be possible to better understand moon's thermal history. Because one thing is clear - the more thrust folds are found, the more the moon shrank in its past", says Carolyn van der Bogert.
NASA's moon probe "Lunar Reconnaissance Orbiter" (LRO) was sent to the moon together with the satellite "LCROSS" on board an "ATLAS V" rocket. The probe contains the "Lunar Reconnaissance Orbiter Camera" which is to bring to light details of the moon that have never been seen before. The mission aims to map the entire surface of the moon in high resolution, search for traces of water ice and measure cosmic radiation levels.