A new era in the exploration of Mars opened 50 years ago this week, when the first of two Viking landers touched down there. The probes measured the weather and the composition of the Martian rocks and dirt. They looked for evidence of life. And they gazed into the sky, showing a reddish tint for most of the day, but blue at sunrise and sunset.
That color is caused by dust in the atmosphere. The tiny dust grains are reddish brown. They scatter some of the sunlight – mostly red light, which makes the sky glow in shades of red. Depending on the time of day, the amount of dust, and other factors, the sky can range from butterscotch to apricot to bright pink.
But as the Sun rises and sets, its light passes through a much thicker layer of the atmosphere. That filters out most of the red light, making the Sun and the sky look blue.
There’s a lot of dust in the sky, and much of it floats quite high above the surface. So sunlight reflecting from the high-altitude dust extends the twilight, making the sky bright even when the Sun is well out of view.
Mars is inching higher into our morning sky. It looks like a fairly bright orange star. It’s in the east at dawn. The star Elnath – the tip of one of the horns of Taurus – stands to the left of Mars. The bull’s eye, Aldebaran, is to the right of Mars. It’s a little brighter than Mars, but about the same color – the color of the Red Planet.
Script by Damond Benningfield