Looking over Mercury’s Horizon

If you didn’t read the title, and I tell you the image below is our Moon, I think all of you will believe me…

To be honest, I may also mistaken it as our Moon if I didn’t read the caption.  Mercury and our Moon just look so similar to us laypersons because they do share some similarities:  they are both full with impact craters across their surfaces, they do not have atmosphere and their rocky surfaces have not experienced much geologic activity for the past 3 ~ 4 billions years.

However, Mercury and the Moon do have important differences.  The most obvious difference between the two is that the Moon has dark area filled with basaltic lavas forming the maria and bright highlands, but Mercury do not.  There is only subtle variations in the brightness of Mercury’s surface.

Mercury Horizon

As the MESSENGER spacecraft drew closer to Mercury for its historic first flyby, the spacecraft’s acquired this image on January 14, 2008, when the spacecraft was about 18,000 kilometers from the surface of Mercury, about 55 minutes before MESSENGER’s closest approach to the planet.  Credit: NASA / JHUAPL / CIW

The image shows a variety of surface textures, including smooth plains at the center of the image, many impact craters (some with central peaks), and rough material that appears to have been ejected from the large crater to the lower right.  This large 200-km-wide crater was named Sholem Aleichem for the Yiddish writer.  In this MESSENGER image, it can be seen that the plains deposits filling the crater’s interior have been deformed by linear ridges.

The shadowed area on the right of the image is the day-night boundary, known as the terminator.

These images are from MESSENGER, a NASA Discovery mission to conduct the first orbital study of the innermost planet, Mercury.


~ by thChieh on March 21, 2008.

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