My colleagues at the Planetary Science Institute published a paper in Nature Astronomy mapping subsurface ice in the northern hemisphere of Mars. The results are quite encouraging. The paper begins with:
PSI press release: https://www.psi.edu/news/morganmarsiceMultiple nations and private entities are pushing to make landing humans on Mars a reality. The majority of proposed mission architectures envision 'living off the land' by leveraging Martian water-ice deposits for fuel production and other purposes. Fortunately for mission designers, water ice exists on Mars in plentiful volumes.
Project website: https://swim.psi.edu/
Nature Astronomy paper: https://rdcu.be/ceYax