Earth’s Moon has captivated astronomers, artists and poets for thousands of years. The Earth’s single natural satellite has enormous symbolic history for humanity which is well documented. What is less well known is the history of the Moon itself. Now, according to NASA, the lunar surface’s ‘wrinkles’ – its ridges, contours and craters – are speaking volumes about its past.
Researchers at the California Institute of Technology, Pasadena, led by Meg Rosenberg, have produced a comprehensive roughness map of the lunar surface based on data collected by NASA’s Lunar Orbiter Laser Altimeter from its Lunar Reconnaissance Orbiter. This is the most detailed map of the Moon’s slopes and roughness ever compiled, and reveals all the wrinkles – everything from huge meteorite impact craters to dark plains of maria left behind by volanic eruptions.
It’s Meg Rosenberg and NASA’s hope that 4.5 billion years of the Moon’s history could finally be revealed by close analysis of this map and other LOLA data.
For example, the roughness of craters on the surface can reveal how old they are, according to Rosenberg: “Old and young craters have different roughness properties—they are rougher on some scales and smoother on others,” with older craters displaying greater roughness as crater walls have been bombarded with fresh meteorite hits over the subsequent millions of years, changing the crater’s original shape and affecting both the texture of the terrain and the angle of slopes.
Oded Aharonson, an advisor to Rosenberg, has been excited by the variety of terrains observable on the moon’s surface: “surfaces roughened by the accumulation of craters over billions of years can be near regions smoothed and resurfaced by more recent mare volcanism.”
The roughness map is being compared with existing contour maps to increase our understanding of the Moon’s wrinkles and its past. By comparing the two, researchers can get an idea about the processes which shaped the Moon as we know it. One example is the huge Orientale crater, created when a huge object crashed into the Moon. The roughness map has indicated subtle differences in the roughness of the debris surrounding the impact crater, and adds to the information which can be gleaned from a contour map showing how high or low the different parts of the crater are. In this way we can learn more about the kind of object which might have struck our Moon, and the angle at which it hit.
Rosenberg’s team have chosen the Moon for this study as the nearest non-terrestrial body and the most well-charted. But Rosenberg is already speculating that Mars could be ripe for the same kind of analysis, even though the processes which shaped the Red Planet will clearly be very different from our nearest neighbour in the night sky.
