There is only one file type that uses the .MART extension:
MartView eBook File
E-publication file used by MartView, a free program used for reading eMagazines and eBooks; includes book or magazine pages and pagination information; used for downloading and reading e-publications in the MartView reader.
MART files can be created from .PDF files, .ZIP and .RAR files, Comic book archives (.CBZ and .CBR), as well as from several raster image formats, including .JPG, .PNG, .GIF, and .BMP.
Updated: August 22, 2011