On the surface of the Red Planet, normal bodies of water cannot exist for long periods of time under today’s conditions. It’s possible, however, that very salty “puddles” or reservoirs of liquid (“brines” in technical language) could remain stable on or just below the surface for some amount of time, especially during the Mars spring and summer months, when ice deposits thaw. Whether these puddles are suitable for life as we know it, however, remains questionable.
In 2018, reports sparked headlines that these brines might have conditions that are friendly to life after all. One factor speaking for this was that oxygen would dissolve very well in the brines under the conditions prevalent on Mars. While our neighboring planet’s atmosphere has only 0.145 percent oxygen (Earth: 21 percent), the brines might be relatively rich in oxygen and could therefore provide a foundation for life for microorganisms.