Given the WAC’s ability to take images through 11 narrow-band color
filters, it is natural to wonder what does Mercury look like in “true”
color such as would be seen by the human eye. However, creating such a
natural color view is not as simple as it may seem. Shown here are four
images of Mercury. The image in the top left is the previously released
grayscale monochrome single WAC filter (430-nanometer) image (PIA11245); the
remaining three images are three-color composites, produced by placing the
same three WAC filter images with peak sensitivities at 480, 560, and 630
nanometers in the blue, green, and red channels, respectively. The
differences between the color representations result from how the
brightness and contrast of each individual WAC filter image was adjusted
before it was combined into a color picture. In the top right view, all of
the three filter images were stretched using the same brightness and
contrast settings. In the bottom left picture, the brightness and contrast
of each of the three filter images were determined independent of the
others. In the bottom right, the brightness and contrast settings used in
the upper right version were slightly adjusted to make each of the three
filter images span a similar range of brightness and contrast values.
So which color representation is “correct” for Mercury? The answer to that
would indeed depend on the eye of the beholder. Every individual sees
color differently; the human eye has a range of sensitivities that vary
from person to person, resulting in different perceptions of “true” color.
In addition, the three MDIS filter bands are narrow, and light at
wavelengths between their peaks is not detected, unlike the human eye. In
general, in light visible to the human eye, Mercury’s surface shows only
very subtle color variations, as seen in the three images here. However,
when images from all 11 WAC filters are statistically compared and
contrasted, these subtle color variations can be greatly enhanced,
resulting in extremely colorful representations of Mercury’s surface, such
as seen in a high-resolution image of Thākur crater (PIA11365).
Date Acquired: October 6, 2008
Image Mission Elapsed Time (MET): 131775256, 131775260, 131775264, 131775268
Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
Resolution: 5 kilometers/pixel (3 miles/pixel)
Scale: Mercury’s diameter is 4880 kilometers (3030 miles)
Spacecraft Altitude: 27,000 kilometers (17,000 miles)
These images are from MESSENGER, a NASA Discovery mission to conduct the
first orbital study of the innermost planet, Mercury. For information
regarding the use of images, see the MESSENGER image use policy.