Is There Really Water on Mars? What NASA Says in 2026

The question of water on Mars is one of the most searched topics in space science — and one of the most frequently misunderstood. Yes, Mars has water. It has water ice at the poles, confirmed beyond any doubt. It has evidence of ancient liquid water in dried riverbeds, lake basins, and mineral deposits that only form in aqueous environments. And, most significantly for anything that might currently be alive on Mars, it has evidence of liquid water existing right now, in the shallow subsurface, in a form kept liquid by chemistry rather than temperature.

The Ice: Confirmed

The Mars Reconnaissance Orbiter's SHARAD radar has mapped water ice deposits across the Martian subsurface with enough detail to estimate volumes. The polar ice caps contain enough water ice that if melted, it would cover the entire Martian surface to a depth of approximately 35 metres. This ice is not going anywhere — it is stable at the poles under current Martian conditions — but it confirms that Mars has not lost all its water. It has moved it.

The Subsurface Lakes: Contested But Supported

In 2018, the MARSIS radar instrument on the Mars Express orbiter detected a radar reflection beneath the south polar ice cap consistent with a subsurface lake approximately 20 kilometres wide and 1.5 kilometres deep. Subsequent analysis has been contested — some researchers argue the reflection could be produced by geological processes rather than liquid water — but the best current interpretation remains a hypersaline subsurface lake, kept liquid by the dissolved perchlorate salts that are widespread on Mars.

The Brines: The Most Practically Significant Finding

The most significant water finding for the question of current Mars life is not the polar ice or the subsurface lakes. It is the perchlorate brine hypothesis: the proposition that liquid water exists right now, at approximately 85 centimetres below the Martian surface, in perchlorate-rich soil where the dissolved salts depress the freezing point to −70°C.

The Phoenix lander confirmed perchlorates in Martian soil in 2008. The Curiosity rover's REMS weather station recorded overnight humidity conditions consistent with brine formation at Gale Crater. The evidence is indirect — no mission has yet drilled to 85cm and extracted a liquid sample — but the chemistry is established and the conditions are met at the right locations.

Why Hellas Planitia

The best location on Mars for subsurface brine stability is the Hellas Planitia basin, at −7,152 metres below the Martian datum. The higher atmospheric pressure at that depth extends the stability range of liquid brines closer to the surface and makes them more persistent across the diurnal temperature cycle. If you were designing a Mars mission to access subsurface liquid water, Hellas is where you would go.

It is also, not coincidentally, where SOLEN detects the 0.3-second signal on Sol 1 of the NovaSeed mission — and where the brine pocket at 85cm maintains a temperature 1.3 degrees above ambient in ways that no purely geological model explains.