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Physics LibreTexts

6.15 Modern Views of Mars

The engineered "canals" of Mars, the vegetation, and the Martian civilization pictured by Percival Lowell and science fiction writers turned out not to exist. But the real Mars is almost as interesting. Modern spacecraft mapping of Mars, as well as Hubble Space Telescope images, show that patchy, streaky markings do cross Mars. These markings partially account for the early reports of canals. Lowell and his supporters misconstrued the patchy streaks as thin, straight lines. In reality, the dark patterns are deposits of wind-blown dust, drawn out into streaks by the prevailing winds. Gigantic dust storms occasionally sweep the planet, altering the configurations of these deposits.


Mariner 9. Click here for original source URL


Mars from?Hubble Space Telescope October 28, 2005 with dust storm visible. Click here for original source URL.



Modern space missions have cleared up other Martian mysteries. One of the Viking orbiters in the 1970s photographed a mountain that looked like a human face under certain lighting conditions. This didn’t surprise planetary researchers, since shadow features of natural mountains on the Earth can also vaguely resemble human or animal forms; it’s like seeing shapes in the clouds. However, some writers and tabloid newspapers seized on the "face on Mars" and claimed it was an artificial structure built by aliens. Extremists even claimed that NASA sabotaged its own Mars Observer mission, which failed in 1993, to prevent the "truth" from coming out! In 1998, the Mars Global Surveyor took a much more detailed picture of this region (among many others), and the photographs showed an entirely natural feature. Many Martian hills are capped with a layer of resistant rock, which erodes into broken ridges and valleys that cast intricate shadows. With different lighting and better resolution, this hill doesn’t look anything like a face. NASA’s Hirise orbiter has delivered images of almost the entire surface of Mars with one meter resolution, good enough to see any object the size of a sofa. That kind of data sweeps away all the ambiguity and mystery.


Global view of Mars as seen by the?Viking?1?orbiter in 1980, showing the?Valles Marineris?(center). Click here for original source URL

 


Two serious points are common to the stories of the purported "face" and “canals” on Mars, apart from the media culpability and public gullibility. First, the human eye and brain tend to see patterns, because that’s what they evolved to do. A baby must learn to recognize its mother’s face, so pattern recognition is learned from birth. The hunter must be able to recognize the predator lurking in a screen of foliage. As a survival skill, it’s clearly more advantageous to occasionally "see" a tiger that isn’t there, than to miss the tiger that really is there! So the human eye tends to detect patterns, even when none exist. However, improved data allows us to test those patterns and choose between rival hypotheses. In this case, better imaging defeated the hypotheses that Martian “canals” and the "face” were anything other than natural rock and dust formations.


Carl Sagan with a model of the Viking lander. Click here for original source URL.

 



Viking 1 Orbiter. Click here for original source URL.


?The?High Resolution Imaging Science Experiment?onboard the?Mars Reconnaissance Orbiter?captured this image of an eroded?mesa?made famous by its similarity to a human face in a?Viking 1 Orbiter?image with much lower?spatial resolution?and a different lighting geometry. Click here for original source URL.