In the photo – this is what Mars could look like if there were oceans, like on Earth.
Essentially, Mars would have one Northern Ocean. In terms of volume, it would reach 17 million cubic meters. This is slightly smaller than the Earth’s Arctic Ocean.
On the left, in the dark red zone, is Mount Olympus. This is the highest mountain in the solar system, which reaches a height of over 22 kilometers.
In the past, liquid water could well have existed on Mars. On the surface of the planet there is a relief that resembles the mouths of rivers. Now the water is concentrated in a layer of permafrost, which goes hundreds of meters deep.
If we add more water, making it proportional, as on Earth, then we already get such a map.
2 billion years ago, Mars could have had quite comfortable conditions for life. The surface of the planet warmed up to +50 degrees Celsius. There was normal, almost terrestrial pressure. Despite the fact that Mars is smaller than the Earth, the atmosphere here was denser, and the pressure, proportionally, turned out to be close to the Earth’s.
This photo shows a reconstruction of what the relief of Mars really could have been 2 billion years ago. When the water was here in liquid form.
Theoretically, at that time, a biosphere could well exist on Mars.
Over time, Mars lost its atmosphere. The first colonists to ever arrive here will most likely build underground colonies. This is the only way to protect yourself from the destructive effects of the solar wind. After all, now Mars does not have a strong magnetic field and atmosphere that save all life on Earth.