Tuesday, October 26, 2010

LROC: Highest Point on the Moon

Updated October 27, 2010 - 2005 UT

Arrow shows highest point on the Moon, 10,786 meters (35,387 feet) above the mean global radius. North is up, Sun's elevation is 16° above the horizon, image field of view is 500 meters, from LROC Narrow Angle Camera (NAC) M133865651L & R mosaic [NASA/GSFC/Arizona State University].

Mark Robinson

Principal Investigator
Lunar Reconnaissance Orbiter Camera
Arizona State University

Over the course of the Lunar Reconnaissance Orbiter mission, the LOLA team has diligently watched as the highest point on the Moon got higher and higher. No, the Moon is not expanding, but rather the LOLA profile coverage increases each month so the chances increase that a ground track will pass directly over, or very near to the highest point. Once the LOLA team had the spot narrowed down to a small area, the LROC team commanded a NAC stereo pair (12 August 2010) to get an even higher resolution measurement of the elevation and coordinates of the highest point. Once the stereo pair was on the ground, the LROC team processed the images into a digital elevation model (DEM), or topographic map.

Another view of the Moon's highest point with the Sun further above the horizon (Sun angle 48°). Image field of view is 500 meters, LROC NAC M136226953 [NASA/GSFC/Arizona State University].

The highest point on the Earth is at the summit of Mount Everest, which is 8,848 meters (29,029 feet) above sea level. The lunar high point is 1938 meters higher than that of the Earth! However there are several major differences between the two points. Mt Everest is a relatively new feature on the Earth. It was formed as tectonic plates collided and pushed up to astonishing heights what was once seafloor, over the course of about 60 million years. The lunar high point is very ancient, and was most likely formed as ejecta from the enormous South Pole Aitken basin piled up during this cataclysmic event, in matter of minutes, more than 4 billion years ago. Another key difference between the two highest points is slope. The flanks of Mt Everest are very steep, while on the Moon the approach to the summit has slopes of only about 3°, assuming you skirt around impact craters. This difference is due to the two very different formation mechanisms.

LROC Wide Angle Camera (WAC) mosaic of the Far side highlands region around the Moon's highest elevation (arrow). Engel'gradt (after Vasilij Pavlovich; Russian astronomer, 1828-1915) crater is 44 km in diameter, north is up, mosaic field of view is 100 km [NASA/GSFC/Arizona State University].

As the LRO mission progresses, knowledge of the spacecraft position improves so the accuracy of the elevation and coordinates (5.4125°N, 201.3665°E (158.6335°W) - 10,786 meters) of the highest point will improve a small amount.

The highest point is near sample 5,654 and line 29,939 in the full resolution NAC mosaic.

Related Post:
Lunar superlatives from LROC WAC
September 6, 2010

More than sixty kilometers north by northeast of the Moon's highest point is a view showing the wide variations of elevation nearby. The base of the ridge immediately below is roughly equal to the global mean average, rising to a hight of 1200 meters in a few kilometers. The distance between that closer ridge and the "plateau-like" ridge on the horizon, upon which is the 10 km highest point, is 55 kilometers. LROC NAC mosaic overlaying lunar digital elevation model available in Google Earth (>v.5).

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