“If Mars had stable oceans for millions of years, what happened to all that water?”
Mars, our enigmatic neighbor, has always been the subject of speculation—could it have once harbored life? For decades, scientists have wondered if ancient oceans once covered the red planet, and whether those bodies of water played a role in the planet’s ability to support life.

In 2021, China’s Zhurong rover brought us closer to answering these questions with groundbreaking discoveries that may change everything we thought we knew about the Martian past.

The Search for Water on Mars: Could Ancient Oceans Have Once Existed?
Mars has fascinated scientists for centuries, mainly due to its striking similarities to Earth.

It’s often referred to as our “sister planet” because of its similar size and structure, but unlike Earth, Mars is a cold, arid desert today.

However, evidence suggests that millions of years ago, Mars may have been a completely different world—one with liquid water, possibly oceans.

Several missions have shown signs that water once flowed freely on Mars, leaving behind ancient riverbeds, polar ice caps, and minerals that only form in the presence of water.

The discovery of water is vital because it raises the possibility that Mars could have supported life in its distant past.

Yet the big question remains: What happened to all that water, and could Mars have had stable oceans in the past?

Zhurong’s Mission: Unveiling Mars’s Hidden Secrets
In May 2021, the China National Space Administration (CNSA) made history with the successful landing of the Zhurong rover on Mars.

As part of China’s Tianwen-1 mission, Zhurong was tasked with studying Mars’s surface, geology, and climate.

Its primary goal was to explore the Utopia Planitia, a region thought to have once been an ancient ocean basin, based on earlier satellite mapping.

The rover, equipped with 13 scientific instruments, began studying the region’s geology and searching for signs of water and past habitability.

Among its tools were radar systems to detect subsurface features, spectrometers for rock analysis, and atmospheric monitors to study Mars’s climate.

But what Zhurong uncovered in this ancient ocean zone was far more intriguing than anyone had imagined.

The Key Discovery: Evidence of an Ancient Martian Shoreline?
Zhurong’s radar imaging uncovered striking geological features that closely resemble Earth’s coastal regions.

The rover detected a series of reflectors that sloped at angles between 6 and 20 degrees, pointing towards a 1.3 km stretch of terrain.

This was highly unusual because geological structures in Mars’s arid environment don’t typically form with such consistent slopes.

These features aligned with what we would expect to see in a foreshore zone—a part of the coastline where the land meets the ocean and sediment is deposited by tides and waves.

This discovery is the strongest evidence yet for the theory that Mars once had standing bodies of water—perhaps even oceans—during its early history.

The reflection data, combined with previous satellite observations, suggests that the area was once a dynamic coastal environment, where waves, tides, and river systems could have played a role in the development of life-supporting conditions.

The Faint Young Sun Paradox: How Could Mars Have Supported Water?
The discovery of a possible shoreline raises an important question: How could Mars have sustained liquid water, especially given that the Sun was much weaker billions of years ago? This issue is known as the Faint Young Sun Paradox.

The Sun, when Mars was likely warm and wet, was about 25% dimmer than it is today, meaning that Mars should have been too cold to support liquid water.

One explanation for this paradox is that Mars may have had a much thicker atmosphere in its early history, rich in greenhouse gases like carbon dioxide, which could have trapped enough heat to keep the planet warm.

Some scientists believe that volcanic eruptions or asteroid impacts could have released these gases, providing a temporary warming effect that allowed liquid water to persist on the surface.

Venus, Earth, and Mars: Why Did They Evolve So Differently?
As we explore the possibility that Mars once had oceans, we must also consider why Mars evolved so differently from Earth.

Despite being similar in size and mass, Venus, Earth, and Mars have drastically different climates.

Earth has abundant liquid water, a stable atmosphere, and life, while Venus is a hellish, toxic world, and Mars is cold and dry.

Mars’s change in climate, likely due to the loss of its atmosphere and water over time, is still a mystery.

Was it the loss of its magnetic field that allowed solar winds to strip away its atmosphere? Or did it experience a catastrophic event that led to the depletion of its water sources? These are questions that scientists hope to answer as they continue studying Mars and its geological history.

The Future of Mars Exploration: What’s Next?
NASA’s future missions, including VERITAS and DAVINCI, are set to further explore the possibility of past water on Mars and investigate the planet’s complex geological history.

However, the fate of these missions is uncertain due to potential budget cuts in the U.S. space program.

But with increasing global interest in Mars exploration, including plans from China, the UAE, and private companies like SpaceX, the exploration of Mars will continue to thrive.

The discovery made by the Zhurong rover is just the beginning of what could be a new chapter in our understanding of Mars.

With new missions planned in the coming decades, we could finally uncover the full story of Mars’s water, its potential for life, and its role in the evolution of our solar system.