Planetary scientists concur that Mars once boasted liquid water and a water-rich atmosphere, drastically different from its current arid state. However, extensive research has revealed a significant anomaly regarding the fate of this ancient water. Despite discerning various sources of water that once flowed on Mars, we still question where it all disappeared.

The Noachian Era, occurring between approximately 4.5 to 3.7 billion years ago, is believed to be the time when Mars had significant surface water. Current estimates suggest there was enough water to envelop the entire planet in an ocean ranging from 150 to 250 meters deep at the end of this period.

However, Bruce Jakoski and his research team from the University of Colorado discovered that, based on their assessment of water removal processes, the total depth might only reach a few dozen meters. This work was presented at the Lunar and Planetary Science Conference (LPSC) in Texas on March 20.

Today, the available water near Mars’ surface is predominantly in the form of ice and hydrated minerals—roughly equivalent to Earth’s ocean, which is approximately 30 meters deep. “How can we transition from a distance of 150 meters down to merely 30 meters? This is perplexing,” remarked Jakoski, emphasizing that our current understanding of Martian water loss is far from complete.

Several theories exist regarding where the water went. It might have evaporated into space in greater quantities than previously considered, become trapped in undiscovered ice reserves, or suggested environmental interactions between ice caps and atmosphere may have been misunderstood. Jakoski believes it’s likely a combination of these mechanisms alongside others.

While the significant discrepancy surrounding Martian water is indeed surprising, it underscores that our understanding of the planet’s hydrological history remains incomplete. Other researchers at LPSC have proposed the notion of intermittent rainfall followed by droughts, suggesting that Mars’ water cycle might significantly differ from Earth’s.

“This indicates that Mars’ water cycle might be fundamentally different from Earth’s,” stated Eric Hyatt from Washington University in St. Louis. His findings propose that Martian groundwater may not interact with the surface and atmosphere as previously thought, potentially altering our comprehension of the water influx to Mars’ surface.

Moreover, Bethany Alman from the University of Colorado posits that there may exist more water on Mars than we initially thought. This situation highlights that while considerable knowledge about Mars has been amassed, a comprehensive picture of its water history remains elusive.

Deciphering the secrets of Mars’ water and its implications for potential habitability throughout its history will pose a monumental challenge. “How do we advance from here? We can’t just introduce more models,” Jakoski stated. “We must engage in boots-on-the-ground exploration.”

NASA and SpaceX have both prioritized lunar exploration. Given that it might take decades before humans arrive on Mars, progress will be gradual, utilizing data collected from rovers and orbiting satellites.

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