Mars is a frozen world today. However, throughout history it has experienced periods of warmer temperatures, with flowing rivers and seas, melting glaciers, and possibly abundant life. Changes in the Martian climate can offer clues about the evolution of other planets, which is why research has intensified to understand the climate on Mars and find evidence of a possible ocean.
However, today, Mars has a parched surface in which the amount of water in its atmosphere often condenses into frost, especially near its north pole. In that area it forms perennial ice caps. What happened to the climate of Mars?
The surface and atmosphere of Mars
Although it may seem surprising, even though CO2 retains heat, a large amount of frozen CO2 resides in the south polar region of Mars. The surface of this planet shows no signs of water, except in some frosty areas or in the form of valleys carved by ancient floods. For more details about the Martian soil, you can consult this article.
The atmosphere of Mars is cold, dry, and thin. This thin veil, composed mostly of CO2, creates a surface pressure less than 1% of that recorded at sea level on Earth . Mars' orbit is 50% farther from the Sun than our planet's. Furthermore, its atmosphere is extremely thin, contributing to its frigid climate. Average temperatures are -60 degrees Celsius, reaching as low as -123 degrees Celsius at the poles. This data is vital for understanding climate change on Mars.
Quite the opposite. The midday sun is capable of heating the surface enough to produce occasional thawing , but the low atmospheric pressure causes the water to evaporate almost instantly.
Although the atmosphere contains a small amount of water and water-ice clouds sometimes form, the Martian climate is characterized by sandstorms or blizzards of carbon dioxide. Each winter, a blizzard of frozen carbon dioxide sweeps across one of the poles, and as the frozen carbon dioxide evaporates at the opposite polar ice cap, several meters of this dry ice snow accumulate. But even at the pole where it is summer and the sun shines all day, temperatures don't rise high enough to melt this frozen water.
The past of Mars
Most of Mars' craters are heavily eroded. Around almost every younger, larger crater, mudflow-like structures are visible . These muddy deposits are likely frozen remnants of ancient cataclysms—asteroid or comet collisions with the Martian surface—that melted areas of the frozen permafrost and carved enormous holes deep underground into zones containing liquid water. This underscores the importance of understanding how Mars' past influences its current climate.
Evidence has been found that ice once formed on the surface, creating typically glacial landscapes. These include rocky ridges formed by sediment left behind by melting glaciers and meandering ribbons of sand and gravel deposited beneath glaciers by rivers running beneath the ice sheet. To learn more about the climatic evolution of Mars, visit .
It is possible that the water cycle on Mars included components related to wet periods. A dense atmosphere would most likely have contained a considerable amount of water evaporated from lakes and seas. This water vapor would condense to form clouds and eventually precipitate as rain. The falling water would create runoff, much of which would seep through the surface. Meanwhile, snowfall would have accumulated, forming glaciers, which would have discharged their meltwater into glacial lakes, highlighting the climate change the planet has undergone.
Some of the images taken of Mars reveal the existence of enormous drainage channels carved into the surface. Some of these structures measure more than 200 kilometers wide and extend for 2000 kilometers or more. The geometry of these drainage channels indicates that water could have traveled across the surface at speeds of up to 270 kilometers per hour.
A lost ocean?
In some high-altitude areas of Mars, there are extensive valley systems that drained into sedimentary depressions—low-lying areas that were once flooded. But these lakes were not the largest accumulations of water on the planet. During recurring floods, the drainage channels flowed northward, forming a series of transient lakes and seas. As can be interpreted from photographs, many of the features observed around these old impact basins mark the areas where glaciers discharged into these deep bodies of water. This research may shed light on the terraforming of Mars.
According to various calculations, one of the largest seas in the northern reaches of Mars could have displaced a volume equivalent to that of the Gulf of Mexico and the Mediterranean Sea combined. It is even possible that an ocean existed on Mars. Evidence for this is based on the fact that many features of the northern plains resemble coastal erosion. This hypothetical ocean was named Oceanus Borealis. It is estimated to have been about four times larger than our Arctic Ocean, and a model of the Martian water cycle was proposed that could explain its formation.
Most planetary scientists now accept that large bodies of water formed recurrently in the northern plains of Mars, but many reject the idea that a true ocean ever existed. However, this debate continues to offer an avenue for investigating climate change on Mars.
Climate Change
In a young Mars, vigorous erosion may have smoothed the surface. But later, as it progressed toward middle age, its face became cold, dry, and scarred. Since then, there have likely been only a few scattered temperate periods that rejuvenated its surface in certain areas. This evolution is crucial for understanding how climate change affects Mars.
However, the mechanism that alternates between mild and severe climates on Mars remains largely a mystery. At present, only rudimentary explanations of how these climatic changes might have occurred are possible. One hypothesis for Martian climate change is based on the tilt of its rotational axis from its ideal position, perpendicular to the orbital plane. Like Earth, Mars is currently tilted by about 24 degrees . This tilt varies regularly over time. It also changes abruptly. Every 10 million years or so, the tilt of the axis sporadically covers up to 60 degrees. Furthermore, the orientation of the tilt axis and the shape of Mars' orbit change over time, following a cycle.
These celestial mechanisms, especially the tendency of the rotational axis to tilt excessively, give rise to extreme seasonal temperatures. Even with a thin atmosphere like the one that currently covers the planet, summer temperatures at mid and high latitudes could have continuously exceeded freezing for weeks during periods of high tilt, and winters would have been even harsher than they are today. The effects of climate change on Mars are a very active area of ​​study.
