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Radio astronomers from the Arecibo Observatory captured this Earth-based data revealing Mercury has radar-bright materials at its poles. These materials have radar characteristics that are best matched elsewhere in the solar system by water ice: radar-bright materials shown in red, radar-bright materials shown in black. (NOTE: depending on the order in which you layer the data, one color might stand out better than the other.)
During the 6.5 year journey from Earth to orbit about Mercury, the MESSENGER spacecraft flew past Mercury 3 times. During these flybys the spacecraft was near the equator, so only some of the north polar region was photographed: Mariner 10 and MESSENGER flyby images.
On March 18, 2011, MESSENGER became the first spacecraft to orbit Mercury! With that remarkable feat came mountains of data, including imaging coverage of 100% of the planet: MESSENGER orbital images.
Along with spectacular images of Mercury, MESSENGER collects data from several other instruments, including the Mercury Laser Altimeter (MLA). The MLA instrument maps the surface of Mercury, producing a topographic map: MLA topography data.
Two tools that might help you get your bearings on Mercury’s north polar region are: north pole coordinate grid, crater names.
As you know by now, discovering water-ice on Mercury did not happen overnight! Let MESSENGER science team member Nancy Chabot and engineering team member Alice Berman help you learn about the long scientific process that has led to this dramatic conclusion. This video captures their presentation for a teacher workshop in which scientists and engineers talked about the challenges (and great benefits) of space exploration. [Watch it HERE] Or explore the other talks and materials presented during this workshop: [Bios, presentations, and other videos]
Do you want more of the science behind this discovery? Watch the NASA Press Conference where MESSENGER scientists share their data in support of water-ice on Mercury. [Watch the Press Conference] [Supporting images, graphics, and videos]
One of the reasons water-ice remains stable on the planet closest to the Sun is the fact that Mercury's spin axis is not tilted like Earth's. Mercury's spin axis is nearly vertical, so very little sunlight reaches the poles. Moving away from the poles, small changes in the topography, such as crater walls, create areas of permanent shadow. Watch this animation depicting the illumination of the topography near Mercury's north pole over about one Mercury solar day (176 Earth days), showing the small proportion of sunlight that reaches Prokofiev crater's floor and rim. How do the shapes of the shadows change as the craters are further from the Sun? [Watch the video and learn more HERE]
The Mariner 10 spacecraft flew by Mercury 3 times in 1974 and 1975, capturing these images of the north polar region: Mariner 10 flyby mosaic.