As MESSENGER neared Mercury on January 14, 2008, the spacecraft's
Wide Angle Camera on the Mercury Dual Imaging System (MDIS) took images of
the planet through each of its 11 filters. This image of the planet's full
crescent was taken using the 7th filter, in light near the far-red end of
the visible spectrum (750 nm). The image shows portions of Mercury
previously seen by Mariner 10, but when Mariner 10 flew by the planet at
each of its encounters the Sun was nearly overhead. For this MESSENGER
flyby, in contrast, the Sun is shining obliquely on regions near the
day/night boundary (called the terminator) on the right-hand side of the
crescent, revealing the surface topography in sharp relief. This image
illustrates how MESSENGER, during its future flybys and subsequent orbital
mission, will teach us much about the portion of Mercury already imaged by
Mariner 10, and not just because of its superior camera and close
proximity to the planet. The solar lighting geometry makes an enormous
difference.
This picture provides a global context for the MDIS Narrow Angle Camera
(NAC) images taken while MESSENGER was inbound. For example, the NAC image
of the crater Vivaldi (PIA10175), released earlier this week,
would fit as a small patch on the terminator just above the center of the
crescent. The already released image that includes the crater Sholem
Aleichem (PIA10176) shows a part of Mercury near the top of the
crescent. More NAC images of the incoming crescent will be released in the
future.
This image was taken about 80 minutes before closest approach from a
distance of about 27,000 kilometers (17,000 miles) and shows features as
small as 10 kilometers (6 miles).
Mission Elapsed Time (MET) of image: 108820027
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.