Final answer:
MLA in the context of Mercury stands for Mercury Laser Altimeter, an instrument that measures the topography of Mercury's surface.
Step-by-step explanation:
In the context of Mercury, MLA stands for Mercury Laser Altimeter. This instrument is used to map the topography of Mercury's surface by measuring the time it takes for a laser pulse to travel from the spacecraft to the surface of Mercury and back. It's a crucial component of missions like NASA's MESSENGER, which orbited Mercury between 2011 and 2015. An altimeter like this helps scientists understand the planet's geology and topography in great detail, contributing to our knowledge about one of the least understood planets in the solar system.