Slope streaks on Mars seen by HiRISE camera onboard NASA's Mars Reconnaissance Orbiter. Image Credit: NASA/JPL/University of Arizona

NASA’s Mars Reconnaissance Orbiter (MRO) has captured this intriguing image of mysterious looking dark streaks on the Martian surface. But what are these unusual features? Why are they so dark? The explanation offered by scientists is much simpler than we think.

It might seem like these are dust streaks gliding across the surface; however, this isn't the case. The darkened areas are places where we see a dust-free surface on Mars. The reddish dust is much lighter than the terrain beneath it. The image above, acquired by MRO scientists on Mar. 9, 2015, shows the dust literally scraped off the slopes, as it has probably slumped downhill. The researchers explain that these slope streaks might be caused by Marsquakes or nearby meteorite impacts, as they always seem to form very quickly.

The image was taken by the HiRISE (High Resolution Imaging Science Experiment) camera onboard the MRO spacecraft.

Of course, the streaks come in a variety of tones. The lighter streaks are slowly getting buried by fresh dust, so that they fade back into their brighter redder surroundings. Scientists try to estimate how long this fading takes to happen, concluding that it's probably close to a few decades. Having in mind that dust is an important factor influencing the weather and climate on Mars, images like this are used to monitor slow changes in these streaks over time to better understand how much dust is settling on the surface.

As most of us are probably aware, the surface of Mars is covered in a thin layer of reddish dust, and the atmosphere also contains a significant amount of dust. On the Red Planet, dust storms occur that can cover even the entire planet for a whole month. The dust on Mars is believed to be globally mixed because of the storms.

Image via NASA Curiosity Rover shows blue sunset on Mars, which results from the angle of the light as it passes through the dusty atmosphere, compared to how the planet looks at noon.

The increased dust in the air is also seen as a haze in images that are sent to Earth. Recent findings reveal that the hazy, Martian dust is dangerous to human health. It contains fine-grained silicate minerals, which reacts with water in human lungs and creates damaging chemicals. Of course, this could be perceived as another serious hazard for future Mars colonists.

Moreover, the MRO spacecraft is tracking the dust storms constantly, as monitoring the storms is not just a human concern; it's also important for Mars rover operations. More dust in the air means more dust falling onto a spacecraft’s solar panels, which will reduce the solar-powered rover's energy supply for daily operations.

Also, as an interesting aside, the camera that captured the featured image consists of a powerful 0.5 m (19.7 in) aperture reflecting telescope, the largest so far of any deep space mission, which allows it to take pictures of the Martian surface with resolutions of 0.3 m/pixel (about 1 foot), resolving objects below a meter across. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona.

The image above, acquired by MRO scientists in 2015, shows the dust literally scraped off the Martian slopes.

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