An Ocean on Mars

An illustration of the probable size and location of the ocean on Mars.
Image: University of Colorado

There has been a large and increasing amount of evidence for the past presence of liquid water on Mars, perhaps even in large quantities. However, recently, a new study conducted by scientists at the University of Colorado at Boulder suggests that there was a large ocean, stretching across a third of the Martian surface, about 3.5 billion years ago.

Previously, many scientists have speculated and used several pieces of evidence to suggest that oceans have existed on Mars. But the idea has also been challenged and questioned many times. New research conducted by Gaetano Di Achille and Brian Hynek is giving more proof for the previous existence of an ocean.

The scientists' findings show that 29 of the 52 deltas that they investigated were situated at about the same level 3.5 billion years ago, suggesting that they were part of the same body of water. These deltas probably created the border, or the shoreline, of an entire ocean in the northern part of Mars. Di Achille and Hynek were the first to integrate the various sets of data collected from NASA and ESA's missions orbiting around Mars. Some of the data dates back to 2001.

The ocean that Di Achille and Hynek generated from their research using a Geographic Information System (GIS) covered about 36 percent of the planet, containing about 124 million cubic kilometers (or 30 million cubic miles) of water. This much water would be enough to create a layer of water 550 meter (1800 foot) deep across the entire Martian surface! The ocean would have contained about 10 times less water than the entire volume of the Earth's oceans, while the area covered would be larger than that of the Atlantic Ocean.

Furthermore, an additional study conducted at the University of Colorado at Boulder detected about 40,000 river valleys on Mars, about 4 times the number previously identified. Combining the results of he two studies paints an exciting picture of what existed on Mars. The river valleys were the source for the sediment that was eventually dumped into the deltas. And putting together the extremely large number of river valleys, the river deltas, and the large ocean, suggests that there probably was a global water cycle earlier in Martian history, similar to what exists on planet Earth today.

This research also leaves very intriguing implications for the presence of life on Mars. On our own planet, where there is a large abundance of life, oceans provide a nurturing environment for life and river deltas readily embed signs of it, like organic carbon. For future missions to the surface of the red planet, deltas may prove very valuable targets for hints about past life.

So at this stage, the obvious question is, where did the water go? A study from a few years ago suggested that the disappearance may be due to solar flares and the solar wind. Since Mars is a lot smaller than the Earth, its molten core probably cooled down quickly, resulting in the planet to lose its global magnetic field. In fact, the red planet currently does not have a magnetosphere. On the Earth, a magnetosphere helps protect the atmosphere from the harmful effects of the solar wind, solar flares, and high-energy particles. Without the protection, the Martian atmosphere is vulnerable, and over time most of the Martian atmosphere has been lost. Right now, due to the very low atmospheric pressure on Mars, liquid water cannot exist on the Martian surface (with the exception being the lowest elevations, and even then for extremely short periods).

A combination of findings and research is now helping depict the entire history of water on Mars. From the large ocean, to the dry place it is today. Yet, the story is not complete, and what we know only makes up small chunks of the entire story. A lot is still changing and added on to what we know about the red planet's relationship with liquid water.