First map of the "wrinkles" of the moon

The unevenness and roughness of the terrain reveal the age and striking processes of the lunar landscapes

Map of the elevations and "roughness" of the lunar surface in three different orders of magnitude. Surfaces appearing on a small scale like the oceans appear blue, very rough terrain of young craters appears white and ejecta appear orange. © NASA / GSFC
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For the first time, a new map reveals not only the location of the craters on the moon, but also the roughness of the terrain: From altimeter data, researchers reconstructed the height differences of the surface in different orders of magnitude for this atlas. They provide valuable information about the age and formative processes of lunar landforms. The methodology now presented in the "Journal of Geophysical Research" could also be used for other celestial bodies.

The surface of the moon bears clear traces of its four and a half billion years of history: its plateaus are dotted with large and small craters, the condition of which reveals valuable information about their age and thus also about events and events in the past of the moon. The roughness of the terrain and the steepness of the ascents and slopes in different size scales provides information about whether the crater is already very old and eroded or relatively young.

Measure the ups and downs of the terrain

To investigate exactly this, a research team of the California Institute of Technology (Caltech) in Pasadena has now for the first time created a comprehensive map of the lunar surface that specifically shows the roughness and thus the age of the individual craters and landscapes. The maps are based on data collected by the Lunar Orbiter Laser Altimeter (LOLA) aboard NASA's Moon Probe Lunar Reconnaissance Orbiter. In these elevation data, the researchers painstakingly measured the various slopes of crater walls and slopes.

"The key is to look at the roughness on both a large and a small scale, " explains Meg Rosenburg, lead author of the study. "Older and younger craters have different roughness properties - they are rougher in some sizes but softer in others." The scientist and her colleagues therefore determined the slope of the terrain between two different distant points - the series of measurements each extended from 17 meters to to 2.7 kilometers away.

Clearly recognizable by its orange color ejecta around this older impact crater. The interior of the crater is smooth, filled with lava rock. NASA / GSFC

New look at oriental basin and ejecta

For the first time, the result map reveals the variety in the age structure of the lunar landscape: The most recent craters, not yet influenced by later inclusions, now stand out clearly. The differences and demarcations existing in the smallest space are also clear: In the extreme case, directly adjacent to surfaces which have been roughened by inclusions over billions of years, are flat areas that have been leveled by young maarvulcanism, Oded Aharonson also explains from Caltech. display

The map also provided initial insights into past events. For example, the roughness mapping of the terrain around the Orientale Basin revealed the subtle differences in the distribution of the ejecta, the material in which Impact of a huge object was ejected. Combined with a contour map that illustrates the highest and lowest points, new information emerges.

"By looking at both together, we can say that parts of the Orientale basin are not only higher or lower, but that they are also different degrees of roughness, " Rosenburg said. This in turn gives us some clues about the impact process that slipped out of the ejecta and also about the processes that further changed the surface later.

Also conceivable for planets or asteroids

The new method of roughness measurement could also be used in other celestial bodies than the moon for the investigation of the surface processes. The respective processes are different on Mars than on an asteroid, but they all leave their signature in the topography, which we can interpret, says Rosenburg. "By examining the roughness in different scales, we can begin to understand how our closest neighbors became what they are today."

(NASA / GSFC, May 17, 2011 - NPO)