The Mars Orbiter Laser Altimeter was an instrument aboard the Mars Global Surveyor. It measured the distance between the surface and the satellite by shooting down a laser pulse and measuring the time it took to return. Using orbital data these pulses have been converted into altitude measurements.

The MOLA Mission Experiment Gridded Data Records (MEGDR) is the dataset generated from all these individual laser pulses. It can be downloaded at the PDS MOLA website.

1.1. Loading MOLA data into GIS

Since the MEGDR files are just binary files, the GDAL library is able to read these with some directions. First download one dataset in the desired resolution from for example here for 32 pixels per degree. You need to download both the megt*.img as well as the megt*.lbl.

1.1.1. GRASS

In GRASS you can use the following command:

r.in.bin -b -s input=/path/to/megdr/meg032/megt90n000fb.img output=mars_mola_032 bytes=2 north=90N south=90S west=180W east=180E rows=5760 cols=11520

Where -b means the data needs to be byte-swapped. -s means the data is signed. The boundaries can be acquired from the accompanied label file. Just like the rows and columns.