Ice cliffs as tall as a rugby field is long have been discovered beneath the Martian surface.
US scientists say the find is exciting because it proves for the first time large amounts of frozen water exists away from the poles.
"Each cliff seems to be the naked face of a glacier, tantalising scientists with the promise of a layer-cake record of past Martian climates and space enthusiasts with a potential resource for future human bases," a summary of the research, published in journal Science, reads.
The 100m-high cliffs were discovered using a high-definition camera aboard the Mars Reconnaissance Orbiter, which went into orbit around the red planet in 2006.
"The hunt should now be on… for similar sites closer to the equator."
There are a number of competing plans to get humans to Mars. US President Donald Trump has asked NASA to put people on the surface by 2033.