NASA’s Mars Curiosity rover is still in the infancy of its exploration of Gale crater, but already there’s some tell-tale signs that support the idea that Mars was radically different in past aeons.
Mt Sharp dominates the interior of Gale crater and is the focus of Curiosity’s exploration over the next few years. Pictures can be deceiving, with 18,000 feet in elevation, Mt Sharp is higher than any of the Rocky Mountains.
Mt Sharp is all the more remarkable because it has been formed as the result of geological uplift and erosion.
Look at the separation between the oldest sedimentary layers in the lower half of this image, dating back billions of years, and the uplifted/tilted and yet still parallel sedimentary layers in the younger, upper section. Younger, being a relative term here, as these layers would date back hundreds of millions to billions of years as well, and all of this is laid down before the slow process of erosion reveals what we see today.
If there has ever been macroscopic life on Mars, this is where we’ll find fossil evidence for it, as the planet’s history is revealed here in a geological timeline stretching back billions of years, but what about life now? Could there be some form of life on Mars right now?
We looked at Mars today as a dry, inhospitable desert planet, something like the planet Tatooine from Star Wars, but Mars is more akin to the frozen deserts we see in countries like Chile and Canada, only drier and colder.
Mars has an absurdly low atmospheric pressure.
Temperatures on Mars can be as low as -125F (-87C) and rarely get above 32F (0C), but that’s not the worst Mars has to offer. Even if the Martian atmosphere was breathable (which it isn’t) the air pressure is only 8 millibars (6mmHg), which is what we experience on Earth at 100,000 ft (31,000M).
The average atmospheric pressure is so low on Mars that if you stood outside with a cup of cold water it would boil away in front of you even though its temperature remained near freezing.
With the surface of Mars bathed in solar radiation and toxic CO2, Mars is hostile to life, right?
Well, yes and no… Although this dessicated environment would be hostile to multicellular life, there are bacteria on Earth that consume CO2, can live in sub-zero temperatures (although not to these extremes) and can survive in such a thin atmosphere.
Autotroph is the term used for organisms (bacteria, plants, etc) that produce complex proteins, fats and carbohydrates from inorganic molecules in their environment, using either photosynthesis or chemosynthesis for energy. And we’ve found bacteria at altitudes of up to 50,000 ft (15,000M), so microbes from Earth would struggle to survive on Mars, but their task would not be impossible.
Here on Earth, we’ve found microbes thriving well below the surface of the planet.
Scientists recently retrieved bacteria three-quarters of a mile beneath the sea floor, reaching into a geological strata known as the gabbroic layer, something that’s significant not because of its depth, but because this is the last, lowest layer of the Earth’s crust before reaching the mantle.
Another microbe, Desulforudis audaxviator, was detected in water two miles beneath the earth within a South African gold mine.
Desulforudis audaxviator relies only on hydrogen and sulfide for food, derived from the breakdown of uranium and other radioactive elements. It’s an evolutionary hermit, having adapted to survive without the sun or oxygen, independent of any food chain. This remarkable microbe comprises an “ecosystem of one.”
And all this raises the stakes for the kind of life that could still flourish on Mars, albeit in dried up lava tubes or in the Hellas basin where higher local air pressures allow liquid water to exist close to or even on the surface, and temperatures can reach a respectable 60F (10C).
The Mars Sample Return mission is slated for 2018, but even with a two-stage return, the mission will only bring 500g of soil back to Earth. When you’re spending eight billion dollars for just over a pound of Martian soil you want to make sure you’re not bringing back beach sand.
In the Martian summer, it’s common to find water flowing out from crater walls. Such unstable ground would be difficult to negotiate, but a sample from here just might be worth eight billion dollars if it reveals life on Mars.