Mars was able to retain a habitable environment 500 million years more

A new study funded by NASA and international partners indicates that the period when Mars had a thicker atmosphere and liquid water oceans may have lasted longer than previously thought.

“Our simulation revealed that three billion years ago, the climate in much of the northern hemisphere of Mars was very similar to that of Earth today, with a stable ocean.” Frédéric Schmidt of Paris-Saclay University, France, co-author of a paper on the research published in the Proceedings of the National Academy, said in a statement.

“Our result contradicts theories that such a northern ocean could not be stable. It also increases the time period for an Earth-like climate on Mars.” he added in a statement.

The late Noahide period (4.1 billion to 3.5 billion years ago) is the period generally believed to be habitable on Mars, with significant rainfall near the equator, as evidenced by the presence of valley networks, features formed by the flowing water erosion.

However, this clement period was not to last, and as the eons passed, Mars gradually slipped into its current climate, with an atmosphere too cold and thin to support liquid water, a necessary ingredient for life, on the surface.

Scientists want to know the length of the habitable period; the longer, the more time there would have been for any possible Martian life to form. The new work extends the potentially habitable period on Mars by about 500 million years, to the late Hesperian era.

“Distinguishing the climate of Mars approximately three billion years ago is challenging because Martian surface features do not appear to fully support a hot and humid or cold and dry climate during that time.”said Michael Way, co-senior author of the paper at NASA’s Goddard Institute for Space Studies, New York.

“A hot, humid climate would have produced extensive erosion by water flow, but few valley networks have been observed from this age. Too cold a climate would have kept any northern ocean frozen most of the time. A moderately cold climate would have transferred ocean water to land in the form of snow and ice. But this would prevent the formation of tsunamis, for which there is some evidence.”

The new simulation revealed that the Martian climate at this time could have been cold and wet. An ocean would have formed in the northern lowland basin, where the atmosphere was denser and warmer. The water would evaporate from this ocean and return to the surface as rain or snow.

In and near the ocean, it would be mostly rain, but in the southern highlands, where the air was cold, it would be mostly snow. The snow would accumulate in extensive glaciers that would flow into the lowland basin, returning water to the ocean.

The model shows that the northern ocean could remain liquid even with global mean surface temperatures below the freezing point of water because ocean circulation can bring warm water from the mid-latitudes to the pole, regionally warming the surface by up to 4.5°. Celsius.

Also, just as a dark asphalt parking lot is warmer than a white concrete sidewalk on a sunny day, liquid water is darker than snow and ice, allowing the ocean to absorb more heat from sunlight.

The current atmosphere of Mars is mostly carbon dioxide and extremely thin, about one percent of Earth’s atmospheric pressure at sea level, but there is evidence that it was thicker in the past.

The model predicted a stable northern ocean if Mars had an ancient atmosphere as thick as Earth’s today, composed mostly of carbon dioxide with 10 percent hydrogen (H2).

Just as a heavy coat traps more heat than a light jacket, a thick atmosphere would have helped warm a young Mars by retaining more heat from sunlight. Furthermore, hydrogen helps the atmosphere trap even more heat, as it is an efficient greenhouse gas, and could have been released by extensive volcanic eruptions or meteorite impacts on early Mars.

The ancient climate of Mars was simulated using the ROCKE-3D Global Climate Model (GCM) developed at NASA’s Goddard Institute for Space Studies. The team used the current Martian landscape and surface elevations, removed all current ice sheets, and included a small northern ocean whose boundaries were set where geological evidence points.

The simulation was one of the first fully coupled GCMs used for Mars. This means that the 3D atmospheric and oceanic components are calculated at the same time, which makes it more realistic.