It’s hard to imagine Mars as a wet place, but that’s exactly what the data and images coming in from the Curiosity rover in Gale Crater are telling us. In fact, Mars is the twin Earth almost had.
3.5 billion years ago Gale Crater was filled with ponds of water, with streams cascading down the ancient basin’s walls, down to its wet centre. Eventually these watercourses dried up, but then perhaps the whole cycle repeated numerous times. Of course the water did eventually go for good.
Unlike Earth, which has a powerful magnetic field protecting its atmosphere, Mars has no such advantage. The solar wind — all those energised particles — just ram straight into it, knocking molecules right out of its atmosphere into space. Which molecules go first? The lightest ones. The hydrogen, the water, the oxygen. What is left is the heavier molecules like carbon dioxide, purely by virtue of the balance between gravitational attraction and the applied force of that solar wind. But that’s planet formation!
How do scientists conclude that there may have been these super wet and dry periods from the geology? By evidence left in the rocks, specifically high concentrations of mineral salts, deposited during periods of evaporation. This is not the first time Curiosity has found evidence of water here. The rover has also unearthed evidence of freshwater lakes.
The Gale crater itself started life with a bang, and is thought to have been formed by one massive impact. Sediment on the floor of the crater was built in layer upon layer of alluvial deposits, drying into a substantial formation over time. This layered rock was later wind-eroded to form the current Mount Sharp, which Curiosity is busily climbing.
So, we know there was water there, and likely there for long periods of time. The 64 million dollar question is, was this wet environment capable of supporting microbial life at the surface, and if so, for how long? How long were evolution’s engines allowed to turn, working to transform that life? And is that life still present?
If not for the weak magnetic field of Mars, we could have had a celestial twin. A planet in our own solar system with water-based life. Now that is something to think about!
Studies like this are invaluable in understanding our own home. As a SF writer, they provide invaluable insights when it comes to building your own planets! Check out my own world-building in The Tau Ceti Diversion.
With the crew dead, and the starship’s fusion drive held back from a lethal explosion, Karic and the surviving officers reach a habitable planet – the last thing they expected was to find it already occupied . . .
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