Messenger: Mercury Surface

MLA coverage (left) of Mercury as May 21, 2011, shown as a polar orthographic projection extending to the equator. 

The altimetric profile (obtained on April 30, 2011) for the MLA track highlighted on the left is shown in detail on the right. 

The length of this profile is about 6000 km (or about 3700 miles).

MESSENGER’s Mercury Laser Altimeter (MLA) in its first 2 months of operation has already built up a grid of ground tracks that span most of Mercury’s surface north of the equator (picture).

These data will provide a very good measure of the shape of the planet’s northern hemisphere. The shape of a planet carries a record of all of the interior dynamical and geological processes that have modified the surface.

Signals from MLA’s laser reflected from the surface can be recovered whenever the spacecraft is within a range of about 1,800 km (about 1,100 miles) from the ground track.

Because of MESSENGER’s highly elliptical orbit, MLA can make measurements only for a portion of each orbit approximately centered on closest approach (Figure 2).

By far the most accurate instrument on MESSENGER for determining the shape of Mercury, MLA is yielding precise topographic measurements of Mercury’s northern hemisphere, but other techniques must be employed to measure the shape of the southern hemisphere.

These complementary techniques include the creation of three-dimensional terrain models from stereo images obtained with MESSENGER’s Mercury Dual Imaging System (MDIS), radio occultations, and MDIS profiling of the planet’s