Science is a far more dynamic process than many realize. The constant upheaval of new measurements and new data forces us to constantly reassess our theories and our very view of how well we know the world.
In 2001, a very interesting image began circulating around the internet. It was of a narrow strip of Mars, captured by the Mars Global Surveyor’s MOC (Mars Orbital Camera, great originality there). It was stored in a large database open to the public, but this image had sat unnoticed next to thousands of others until now.
What did we see? These dark blobs were almost a kilometer across. Well, no one really wanted to say. It kind of looked like lichen:
Or a bacterial colony:
Sir Arthur C. Clarke even suggested that they were some sort of Martian banyan tree. “I’m quite serious when I say have a really good look at these new Mars images,” he said. “Something is actually moving and changing with the seasons that suggests, at least, vegetation.”
There’s only one problem with that, and any schoolchild can point it out to you – Mars is supposed to be a dead planet. No life has been found there, at least not that the unwashed masses have been made aware of. The conspiracy theories soon flew fast and thick – that this was one of many images NASA had suppressed that indicated life on Mars.
In short, we were being manipulated by some sort of New World Order that kept knowledge of Martian life silent in order to… well, no one was really clear on that point. Thankfully, the file clerk of this powerful cabal was so incompetent as to leave these blockbuster images on a public server.
But what could it be if it wasn’t life? There are other processes that can produce similar structures:
such as diffusion limited aggregation. So perhaps imminent takeover of the world via suppressed satellite images wasn’t the first thing we should worry about. Maybe there was a less elaborate explanation.
If all we had to base our assumptions on was that single picture, the debate could rage on for a while. Thankfully a new satellite, the Mars Reconissance Orbiter (MRO), entered the skies of Mars in 2006. On the MRO was one crucial piece of equipment – the High Resolution Imaging Science Experiment (HiRISE) camera. This camera was the largest camera ever carried on a deep space mission – to give you an idea of its capabilities, it could see a beachball on the surface of Mars from orbit.
So what did the new pictures look like? Well…
they certainly weren’t lichen, or bacteria, or banyan trees. These long tortured cracks hundreds of meters long were like nothing ever seen on Earth. What could have caused them? Conventional geologic processes on Earth simply didn’t do things like this.
So what was the alternative? Were we back to thinking it may be life again? Well, perhaps there was an unconventional geologic explanation.
Hypothesis: The [carbon dioxide] seasonal ice in the cryptic terrain is translucent, allowing sunlight to penetrate through the ice to the surface below. The ice then sublimates from the bottom of the slab, eroding channels in the surface below. (H. Kieffer, 2000)
Here’s the idea. Mars is cold. So cold in fact, that in it’s “winter” carbon dioxide will actually freeze into transparent sheets over certain regions of the planet. The key thing here is that the ice is transparent, like black ice on asphalt.
Now, think what happens when bright sun shines on black ice. Where does it start melting from? Well, it doesn’t start from the top like you’d think. The sun shines through the clear ice, heats up the asphalt, and the asphalt melts the ice from the bottom. It might even make tiny river-like channels of water between the ice and asphalt, as the liquid water needs somewhere to go.
But what if you ice isn’t made of water, and instead is made of a gas like carbon dioxide? Suppose the sun shines through the ice, heats up the Martian soil, and starts melting the ice from the bottom. Enormous amounts of gas are produced – but where can it go? Well, first it might start to make little channels under the ice like we thought of before to escape. But if there’s no where to go to, eventually, something has to give.
And so, screaming with pressure, the ice fractures. Gas rushes out of these many cracks, carrying dust and soil with it. So what do we end up with? A giant circular region with fractures, darkened relative to the rest of Mars by freshly spit up soil and dust.
So a deep dark conspiracy theory? Perhaps not. It may not be Martian trees, but it is an amazing geologic process that has never been observed on Earth.