These two images show the same terrain on Mercury as imaged by Mariner 10
in the 1970s and by the MESSENGER spacecraft on October 6, 2008. The
reason they look so different is that the angle that the Sun illuminates
the surface is dramatically different between the two observations. When
Mariner 10 acquired the image on the left, the Sun was high in the sky,
which highlights the relative differences in brightness between geologic
units on the surface. When the Sun is lower in the sky, as was the case
during the second MESSENGER Mercury flyby (right image), shadows become
more prominent and it is easier to see the rugged topography of the
surface. Most noticeably, a peak-ring impact crater with a diameter of
about 150 kilometers (93 miles) is clearly seen in new MESSENGER data,
whereas it was nearly invisible in Mariner 10 data. (View images taken by Mariner 10.)
Date Acquired: October 6, 2008
Image Mission Elapsed Time (MET): 131774839
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Resolution: 430 meters/pixel (0.27 miles/pixel)
Scale: A scale bar is given on the images
Spacecraft Altitude: 25,000 kilometers (16,000 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.
