Amateur astronomers have spotted huge cloudlike plumes erupting from Mars – a phenomenon that scientists are at a loss to explain.
The bright flares, which have now died away, towered higher than anything else observed in the Martian atmosphere. Their tops reached some 150 miles in altitude, more than twice as high as the highest Martian clouds, and they sprawled across 300 to 600 miles, researchers report in this week'sNature, a science journal.
The researchers initially were skeptical, but "we came to the conclusion that what we were seeing is actually real," says study co-author Antonio García Muñoz, a planetary scientist at the European Space Agency. The plumes are "exceptional. … It's difficult to come to terms with this."
This scientific brainteaser first came to light in early 2012, when amateur astronomer Wayne Jaeschke was poring over footage of Mars he had captured at his private observatory. He came across a puzzling image showing the Red Planet with a blob billowing off the planet's rounded edge.
In all his years of peering at Mars, "I'd never seen anything like that," says Jaeschke, a West Chester, Pa., resident who spends about 100 nights a year training his gear on the heavens. He quietly ran the image by a few friends, then circulated it among a larger group of both amateur and professional astronomers.
The image confounded the pros, too. Martian clouds, which are typically made of ice crystals, tend to be wispy, like the thin cirrus clouds seen high in Earth's sky. But these were enormous wide plumes seen on 11 days in March 2012 and again in April 2012. Later, the scientists dug up 1997 images of Mars from the Hubble Space Telescope that show a similar plume.
Perhaps the bright fingers are clouds of ice crystals. But for that to be true, the Martian atmosphere would have to be much colder than expected, the scientists concluded. Perhaps the plumes are a particularly dazzling Martian aurora, like the Northern Lights on Earth. If so, they were 1,000 times stronger than any aurora ever seen on Earth. Further, there's no record of unusual sun activity – an essential ingredient of a spectacular aurora – on the days when the shiny bulges appeared on the planet's profile.
Photos: 10 years on Mars:
An artist rendering released by NASA shows the rover Opportunity on the surface of Mars. <p>An exhibition by the Smithsonian National Air and Space Museum in Washington celebrates the images and achievements of the rovers Opportunity and Spirit on the 10th anniversary of their landings on the Red Planet.</p>
An artist rendering released by NASA shows the rover Opportunity on the surface of Mars. An exhibition by the Smithsonian National Air and Space Museum in Washington celebrates the images and achievements of the rovers Opportunity and Spirit on the 10th anniversary of their landings on the Red Planet. (Photo: NASA via AP)
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  • An artist rendering released by NASA shows the rover Opportunity on the surface of Mars. <p>An exhibition by the Smithsonian National Air and Space Museum in Washington celebrates the images and achievements of the rovers Opportunity and Spirit on the 10th anniversary of their landings on the Red Planet.</p>
  • Rover tracks disappear toward the horizon in a sea of sand between the craters Endurance and Victoria on the Meridiani Plains on Jan. 2.
  • A Jan. 23, 2006, false-color photograph of dune crests was taken by the rover Opportunity at Endurance Crater.
  • An Oct. 9, 2009, photograph shows the landing craft and wheel tracks of the Opportunity rover as it leaves Eagle Crater.
  • A July 14, 2009, photograph from the Mars rover Spirit shows a dust devil moving across the landscape. The rover was taking exposures with different color filters and because several seconds intervened between shots with different filters, the location of the dust devils changed between the exposures.
  • An image taken on May 16, 2005, from the rover Spirit shows the sunset casting a blue glow above the rim of Gusev Crater.
  • A photograph taken by the rover Opportunity on Aug. 11, 2011, shows the west rim of Endeavour Crater.
  • This NASA image released on Jan. 25, 2012 shows a mosaic of images of a windswept vista at the location where the rover Opportunity is spending its fifth Martian winter.
  • An image from the rover Opportunity taken on March 25, 2010, shows the Chocolate Hills rock.
  • A late-afternoon shadow is cast by the Mars rover Opportunity at Endeavour Crater on January 2004.
  • An image of the Mars rover Opportunity on July 19, 2011.
  • The rover Opportunity investigates a rock on June 7, 2013, at Endeavour Crater.
  • This image taken by the Mars exploration rover Spirit on June 9, 2004, shows the Columbia Hills on the horizon.
  • An April 13, 2005, image shows the rover Spirit on the flank of Husband Hill that was produced using Virtual Presence in Space technology.
  • A photograph taken by Spirit's panoramic camera shows a flaky rock called Mimi, center, on Feb. 13, 2004.
  • An image taken by the panoramic camera aboard the Mars rover Opportunity on Jan. 1, 2011, shows the rover's empty lander, the Challenger Memorial Station, at Meridiani Planum.
  • This image provided by NASA shows loose, BB-sized, hematite-rich spherules embedded in a Martian rock like blueberries in a muffin. The Mars Rover Opportunity found this cluster at the Eagle Crater landing site on Nov. 26, 2013.
  • The rover Opportunity snapped a self-portrait at Erebus on Oct. 9, 2006.
  • A shadow is cast by the rover Opportunity on July 26, 2004.
  • One of the first images taken of Mars by the rover Opportunity on Jan. 24, 2004.
  • Jet Propulsion Laboratory Director Charles Elachi, left, NASA administrator Sean O'Keefe and Mars Exploration Rover project manager Pete Theisinger celebrate the successful landing of their second rover, Opportunity, at Jet Propulsion Laboratory headquarters on Jan. 24, 2004, in Pasadena, Calif.
  • This image released by NASA on Jan. 20, 2004, shows the Mars rover Spirit probing its first target rock.
  • The Mars rover Spirit snaps a self-portrait with its navigation camera after its successful landing on Jan. 4, 2004.
  • People celebrate while looking at the first images arriving from Mars after the rover Spirit landed on the red planet on Jan. 3, 2004, at Jet Propulsion Laboratory headquarters in Pasadena, Calif.
Other scientists, however, are reacting with caution to the claims.
Planetary scientist Nicholas Heavens says the Hubble image adds credibility to the claims of something new and strange in the atmosphere of Mars. But he's still not convinced there hasn't been some kind of mistake.
"It's a pretty good argument, but there's a hole or two in it," says Heavens, of Hampton University in Hampton, Va.
Planetary scientist Todd Clancy of the Space Science Institute is more blunt.
"I don't think it's real. … Basic physics says this can't occur," Clancy says, adding that the conditions in Mars's upper atmosphere don't supply the necessary ingredients for clouds.
In response, study co-author Agustin Sánchez-Lavega, a planetary scientist and physics professor at the University of the Basque Country in Spain, notes that 19 different observers captured the strange eruptions. He considers the source of the formations "open to discussion," he says via e-mail.
As an amateur, Jaeschke is happy to let the academics argue over what exactly he saw.
Amateurs "only dabble," he says, so it's "exciting … (to) have seen something that stumped the professionals."