Photography has only existed for a minute fraction of humanity's time on Earth. In that time, however, we have managed to capture integral moments in the change and development of the human race.

This photo was taken on April 15, 2015. At first glance, this photo looks like an amateur photo of the sunset on a mountain. What is remarkable about this photo, however, is that it was taken on Mars, by NASA's rover Curiosity. This photo is helping scientists understand what Mars' environment is really like; even the most minute details like the color of the sunset are important observations.

For just a moment, you think, Mars doesn't look so bad. It looks peaceful; boundless. When it hits you, though, that the photo was taken by a robot on a planet 140 million miles away, where the average temperature is -67 F and where life hasn't existed for 15 million years, you become confused. Obviously, the planet isn't inhabitable as we think of it. Humans would need special suits and liquid everything to survive even for just a few years.

The natural next thought that comes to your mind is this: one day, will some far-distant alien race send their own rover to Earth? Will they be captivated by our vibrant sunsets and diverse ecosystems? Will they see everything that we have created in just six or eight thousand years, or just... fossils? Will their robots take pictures of desolate landscapes that couldn't possibly be easily hospitable? Will they be able to fathom what we did with our time here by the photos that we took, the evidence that we left behind for ourselves to remember?

And how long do we have before our planet is just some rusted, uninhabitable, shell that the next great species will have to don special suits to visit?