The latest images from the Mars Curiosity rover and the HiRise camera aboard the Mars Reconnaissance orbiter have left some Earthlings scratching their heads and wondering: What are those blue rocks?
Well, according to NASA, they’re not blue so much as gray. In a photo released yesterday taken by HiRise, the dunes between Curiosity and Mount Sharp are shown as dark blue waves, appearing like an ocean bed on the more tan martian surface.
But why change the colors?
The answer has to do with sunlight, and the fact that daylight on Earth is, of course, different from daylight on Mars. In order to compensate, images from Curiosity are put through a filter that makes the images appear as if they were taken in Earth’s daylight. The filtering process is called “white balancing.” It’s useful for geologists who, as Earthlings, are accustomed to observing rock formations under Earth’s sunlight. Here, for example, is the image above without the “white balancing” filter:
And here’s another, showing a close-up of a rock formation near the rover that was exposed during the landing:
And now, without the filter:
The filter isn’t absolutely necessary, as the Atlantic’s Alexis Madrigal writes, but it is certainly helpful. And, of course, it’s pretty cool to see Mars through Earth-colored lenses.
It’s worth noting that Madrigal’s take is well worth a read, particularly his observation on “the contingency of our own visual systems.”
But before you head over there, here are the dunes mentioned earlier.
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