Mars is 1/3 the size of earth
Mars has lower gravity than earth.
Mars is colder than earth with avg. temp ~ -50 deg celsius.
Mars has been
a dead planet for a VERY long time.
Mars atmosphere is maybe 1/15th the density of earth, with very limited amounts of oxygen.
Both have two poles
Both have
frozen water presently. Today, martian water is contained in 35 to 100% of dirt extending down 2/3 of way to equator.
Both have a
geologic history of sedimentary rocks, erosion and transport of sediments by flowing water, standing lakes, etc.
Both have a
history of tectonics and surface fault expressions.
Both have
volcanoes in Mars case, really really big ones.