Let's Talk About: The Blue Scorpion of Mars

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People often look at planetary features the same way they do clouds. Craters, crevices, peaks and plains seem so jumbled at times that onlookers can't help but see many surprising pictures. We've seen bugs in the volcanoes of Venus and Grover (yes, the happy-go-lucky monster from "Sesame Street") in Mercury's craters. Even our moon and its shadowy seas of lunar dust show the face of a man singing in space. Next door to the Man in the Moon, the crust of Mars is home to Syrtis Major, or as Italian astronomer Angelo Secchi nicknamed it in 1858, The Blue Scorpion.

Syrtis Major is a Martian plateau spanning 620 miles from east to west until curling northward where it extends 930 miles, thus likening it to the profile of a scorpion. Images from the Hubble Space Telescope show that unlike the rest of the Red Planet, Syrtis Major appears dark in color, more specifically blue-gray. For centuries, astronomers speculated on what caused this colorization. Some thought it indicated the presence of water. Others suggested vegetation. Eventually, we learned that Syrtis Major is composed of hardened, volcanic basalt emerging from beneath the light, windblown dust that gives Mars its predominantly orange-red color.

Furthermore, we learned that Syrtis Major isn't blue but brownish-gray. So what makes The Blue Scorpion blue? The answer is twofold. One, the stark contrast between the dark basalt and the bright orange-red dust tricks us into perceiving more of a blue color when we see Syrtis Major. Secondly, Mars is frequently veiled with bluish-white clouds, and while they hardly alter the appearance of the orange surface, they lend enough coolness to the neutrally colored Syrtis Major to render it blue-gray.

So the next time you catch a glimpse of Mars in your telescope, look for The Blue Scorpion crawling across your lens ... or The Almost Blue Scorpion if you prefer.


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