NASA unveils first global topographic model of Mercury

 The first global digital elevation model of Mercury, showing in stunning detail the topography across the entire innermost planet of our solar system, has been unveiled by NASA's MESSENGER mission.

The model shows a variety of topographic features including the highest and lowest points on the planet.

The highest elevation on Mercury is at 4.48 kilometres above Mercury's average elevation, located just south of the equator in some of planet's oldest terrain.
The lowest elevation, at 5.38 kilometres below Mercury's average, is found on the floor of Rachmaninoff basin, an intriguing double-ring impact basin suspected to host some of the most recent volcanic deposits on the planet.

The model was created using more than 100,000 images acquired by the MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) mission - a NASA robotic spacecraft that orbited the planet Mercury between 2011 and 2015.

Images were acquired with a large range of viewing geometries and illumination conditions, which enabled the topography across Mercury's surface to be determined.

With this 15th and last major data release, the MESSENGER mission has shared more than 10 terabytes of Mercury science data, including nearly 300,000 images, millions of spectra, and numerous map products, along with interactive tools that allow the public to explore those data, NASA said.

"The wealth of these data, greatly enhanced by the extension of MESSENGER's primary one-year mission to more than four years, has already enabled and will continue to enable exciting scientific discoveries about Mercury for decades to come," said Susan Ensor, software engineer at The Johns Hopkins University Applied Physics Laboratory (APL), in US.

The new global model complements an older product released by MESSENGER, the topography map derived from earlier measurements by the Mercury Laser Altimeter (MLA).

Due to the spacecraft's highly eccentric orbit, the MLA was able to make primary measurements only in Mercury's northern hemisphere and near-equatorial region, leaving the topography of most of the southern hemisphere largely unknown, until now.

The new map provides an unprecedented view of the region near Mercury's north pole.
"MESSENGER had previously discovered that past volcanic activity buried this portion of the planet beneath extensive lavas, more than a mile deep in some areas and covering a vast area equivalent to approximately 60 per cent of the continental US," said APL's Nancy Chabot, the Instrument Scientist for the Mercury Dual Imaging System (MDIS).

However, because this region is near Mercury's north pole, the Sun is always low on the horizon, casting many long shadows across the scene that can obscure the colour characteristics of the rocks.

Consequently, MDIS carefully captured images of this portion of the planet when the shadows were minimised through five different narrow-band colour filters.

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