Autore: ExtremeTech

An artist's concept of Mars' west hemisphere, billions of years ago, when it still had its oceans and atmosphere

A long time ago, Mars wasn’t the barren lump of rock and dust that it is today. Evidence gathered by rovers and satellites such as Curiosity and the Mars Reconnaissance Orbiter suggests that, billions of years ago, the Red Planet was once covered in lakes and oceans, and that it had a thicker atmosphere. It may have even supported life. Any water and life is now gone, but once upon a time, Mars might’ve looked a lot like Earth.

In the beautiful images above and below, Kevin Gill has attempted to recreate what Mars may have looked like billions of years ago. The images are somewhere between an artist’s concept and a scientific approximation. Gill used real elevation data to plot out Mars’ oceans, mountains, valleys, and other geological features — but then he used his own judgment to paint in the deserts, forests, and so on, using textures from NASA’s Blue Marble imagery. “There is no scientific reasoning behind how I painted it; I tried to envision how the land would appear given certain features or the effects of likely atmospheric climate. For example, I didn’t see much green taking hold within the area of Olympus Mons and the surrounding volcanoes, both due to the volcanic activity and the proximity to the equator,” Gill says.

The image above is of the western hemisphere of Mars, with Olympus Mons on the left horizon, the Tharsis Montes volcanoes a bit closer to the middle, and the Valles Marineris canyons near the center. In the image below we see the eastern hemisphere, with a slightly more verdant palette. In both images you can see the huge ocean that once filled the Vastitas Borealis basin and covered half the planet.

Mars' east hemisphere, billions of years ago, when it might've been covered in water/atmosphere

There is growing evidence that Mars was once a very wet planet. Most recently, Curiosity trekked across Rocknest, a site that was almost certainly a massive riverbed billions of years ago. Imagery from the MRO, which orbits Mars, has revealed river deltas, gullies, and oceanic coastlines. We’re almost certain that Mars once had a thick atmosphere, too — but because the planet lacks a global magnetic field to deflect solar winds, the atmosphere has been steadily burnt away over the millennia.

The big question, though, is whether Mars ever supported life. Gill’s colorful images clearly postulate that ancient Mars, with surface water and an atmosphere, was once capable of sustaining life. So far, there is little evidence to suggest this was the case — but hey, that’s exactly the evidence that Curiosity is tasked with gathering over the next couple of years.

Another interesting way of looking at these images is to think of them as a futuristic Mars, after human terraforming. If we could successfully build an atmosphere around Mars, and somehow refill the oceans, Gill’s images are a good idea of how the planet would look.

The image below, incidentally, is what Mars actually looks like from space — as seen by the Mars Global Surveyor back in 1999. The white puffs are ice clouds hanging over the Tharsis volcanoes, which you see on the left side of of the image at the top of this story.

Mars, as seen by the Mars Global Surveyor in 1999

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