Water on Mars evidence has been building for decades. Scientists have discovered that Mars was once a wet planet — with rivers, lakes, and possibly even an ocean. Today, water still exists on Mars, but mostly as ice at the poles and liquid deep underground. In this article, we break down every major piece of evidence found so far, and what it means for the search for life on the Red Planet.

How Did Mars Get Its Water in the First Place?

First, it is important to understand Mars’s watery origin. Early in its history — roughly 4 billion years ago — Mars was a very different world. It had a thick atmosphere and a magnetic field strong enough to protect liquid water on its surface.

As a result, rivers carved wide valleys. Lakes filled enormous basins. Some scientists even believe Mars had a vast northern ocean. This era is called the Noachian period, and it lasted from about 4.1 to 3.7 billion years ago.

However, Mars then lost its magnetic field. Without it, solar winds slowly stripped away the atmosphere. Consequently, surface water evaporated or froze. The planet transformed into the cold, dry world we see today — but the water did not completely disappear.

The Strongest Water on Mars Evidence Found So Far

Over the past two decades, space agencies have gathered extraordinary proof. Moreover, each new mission adds another layer to the story. Here is a breakdown of the most compelling evidence discovered to date.

1. Ancient River Channels and Lake Beds

In 1971, NASA’s Mariner 9 orbiter first revealed dry riverbeds on Mars. These were not small streams. Some channels were hundreds of kilometres long. Additionally, they showed signs of massive flooding events in the distant past.

Since then, orbiters have mapped thousands of ancient valleys. In fact, researchers at the Open University recently identified an astonishing 15,000 kilometres of lost river channels in a single Martian region called Noachis Terra — a previously understudied area.

Furthermore, NASA’s Perseverance rover confirmed that Jezero Crater — its landing site — was once a lake roughly 45 kilometres wide. Ancient river delta sediments are clearly visible in the rock layers there.

2. Polar Ice Caps Containing Billions of Litres of Water

Mars has two polar ice caps, and both contain enormous amounts of frozen water. Together, they hold enough ice to cover the entire planet in a liquid layer about 35 metres deep if melted.

The northern cap is made mainly of water ice. The southern cap has a thick layer of frozen carbon dioxide on top, but water ice lies beneath. Therefore, the poles represent the largest currently confirmed water reservoir on Mars’s surface.

Underground Liquid Water: The Game-Changing Discovery

Perhaps the most stunning water on Mars evidence came in 2024 and was confirmed through further analysis in 2025. NASA’s InSight lander — which sat on Mars between 2018 and 2022 — collected seismic data before going silent.

Scientists at UC Berkeley and Scripps Oceanography later analysed that data in a new way. Consequently, they found something remarkable. Between 11.5 and 20 kilometres below Mars’s surface, there is a layer of fractured rock completely saturated with liquid water.

According to researchers, this underground reservoir could cover the entire planet with a liquid layer one to two kilometres deep. That is an enormous amount of water hidden beneath a cold, dry surface.

However, there is a catch. This water is far too deep for any current technology to reach. Even on Earth, drilling 11 kilometres is extremely difficult. Nevertheless, this discovery is still hugely important for understanding where Mars’s ancient water went.

Mineral Clues: Rocks That Only Form in Water

Another powerful line of water on Mars evidence comes from minerals. Certain types of rock only form when liquid water is present. Scientists have found dozens of these minerals on Mars.

In September 2025, researchers from Rice University published findings showing that Jezero Crater’s rocks went through at least three distinct stages of water activity. First, hot acidic fluids. Then, more neutral and habitable conditions. Finally, alkaline water that could have supported microbial life more easily.

Therefore, Mars was not just wet. It went through multiple phases of liquid water activity — each one creating different conditions for potential life.

Underground Water That Kept Moving After Mars Dried Out

One of the most exciting recent findings came from New York University Abu Dhabi in late 2025. Researchers studied ancient sand dunes in Gale Crater — the same area where NASA’s Curiosity rover operates.

Surprisingly, these dunes hardened into rock billions of years ago — but not by pressure or wind. Instead, groundwater seeped up through them from below. The moisture left behind minerals like gypsum as it moved upward through the sand.

Moreover, gypsum is especially useful to scientists because it can preserve traces of ancient organic material. Consequently, these ancient dunes are now considered one of the most promising targets for life-detection missions.

The “Sapphire Canyon” Sample: Closest Hint of Ancient Life?

In July 2024, NASA’s Perseverance rover drilled into a rock nicknamed “Cheyava Falls” inside Jezero Crater. The drilled sample was called “Sapphire Canyon.”

After a full year of scientific review, the journal Nature published the peer-reviewed findings in September 2025. The results confirmed that the sample contains potential biosignatures — chemical clues that could suggest ancient life once lived there.

However, scientists are careful to note that more data is needed. A biosignature is not proof of life. It is simply a signal worth investigating further. The sample also showed clear signs of past water activity, including organic material and chemical reactions that resemble what microbes produce on Earth.

As a result, “Sapphire Canyon” remains the most exciting Mars rock sample ever collected. It will eventually return to Earth as part of the Mars Sample Return mission.

An Ancient Beach on Mars? Yes, Really.

In January 2026, researchers from Imperial College London published another remarkable finding. Perseverance had been exploring the inner rim of Jezero Crater for nearly a year.

There, scientists found the first definitive evidence of an ancient shoreline — a real beach that existed on Mars about 3.5 billion years ago.

Furthermore, the rocks showed signs that subsurface water circulated through them over vast periods of time. Professor Sanjeev Gupta of Imperial College London explained that on Earth, this kind of subsurface hydrothermal environment is known to support microbial life.

Therefore, the ancient Jezero lake was not just a brief event. It lasted much longer than scientists previously believed, significantly extending the window for life to have emerged.

A Complete Timeline of Water on Mars Discoveries

Could Water on Mars Support Life Today?

This is the big question. And the answer, based on current evidence, is: possibly — but only underground.

On Earth, life thrives in extreme environments. Bacteria live in deep ocean vents, in highly acidic pools, and in solid rock kilometres below the surface. These are called extremophiles.

Mars’s deep liquid water zone, if it truly exists as seismic data suggests, would be a similar environment. The water is warm because of geothermal heat. It is protected from harmful radiation by kilometres of rock. Additionally, it interacts with minerals that could provide chemical energy for simple life forms.

However, no life has been detected on Mars yet. Scientists are simply pointing to these water-rich environments as the best possible candidates for further investigation. The Mars Sample Return mission — planned for the 2030s — will bring samples directly to Earth where they can be studied in far greater detail than any rover can manage.