NASA has been trying to dampen expectations for an upcoming Mars announcement after rumors abounded that the agency's Curiosity rover discovered something big.
"Rumors and speculation that there are major new findings from the mission at this early stage are incorrect," NASA officials wrote in a statement on Thursday (Nov. 29). "The news conference will be an update about first use of the rover's full array of analytical instruments to investigate a drift of sandy soil."
The announcement will be made at the Fall Meeting of the American Geophysical Union in San Francisco on Monday (Dec. 3).
In light of this latest saga, we took a look back at the five most overhyped Mars discoveries in years past.
1. Canals on Mars
One of the most famous, and famously wrong, discoveries about our neighboring planet was the 1870s claim that canals had been dug into the Martian crust, thus "proving" the existence of life on Mars.
Prominent astronomer Percival Lowell popularized the canal theory, based on the notion that Mars was once green and wet, but had lately been drying out, so the Martians had engineered canals to route water down from the planet's polar ice caps. [The Search for Life on Mars (Photo Timeline)]
Historians say the canal frenzy was boosted by the widespread excitement over the construction of the Suez Canal, an engineering marvel that was completed in 1869.
The idea of canals on Mars persisted well into the 20th century, until observation technologies were advanced enough to reveal the canals as an optical illusion.
2. Flowing water on Mars
On June 22, 2000, NASA announced it had found evidence for liquid water currently flowing on the surface of Mars.
The news, based on photos of gullies etched across the Martian surface taken by NASA's Mars Global Surveyor, made a big splash.
The gullies seemed to have been formed by flowing water, and debris and mud deposits nearby suggested liquid water as well.
What's more, researchers at the time judged the structures to be freshly formed, implying that liquid water exists on Mars today.
However, in the more than 10 years since the announcement, scientists have yet to confirm the gullies are caused by flowing water, or offer definitive proof of water on Mars today.
While experts mostly agree that water ran over Mars' surface in the ancient past, there is lingering disagreement over the present day.
3. Face on Mars
A black-and-white photo of Mars taken by NASA's Viking 1 orbiter in 1976 quickly captivated the public because it revealed an eerie likeness of a human face on the planet's surface.
Although NASA scientists just as quickly judged it to be a naturally occurring outcropping of rock, accentuated by light and shadow, many people searched for a deeper explanation.
Some fixed on the idea that the formation was constructed by an alien civilization, and looked for further signs of a crumbling extraterrestrial city in the region.
The "face on Mars" has been imaged in higher resolution by subsequent NASA missions, which have bolstered the optical illusion explanation.
Still, the uncanny allure of the structure has never totally faded. [Photos: The 'Face on Mars' and Other Illusions]
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