Image: Meteor analysis
F. Selsis et al. / NASA / Nature
The background image shows a meteor near the top left and the horizon at the bottom. A red arrow shows the direction of travel. The inset is a larger version of the meteor. The graph is a "light curve" that aided in tying the meteor to Comet Wiseman–Skiff.
By Senior science writer
updated 6/1/2005 6:35:26 PM ET 2005-06-01T22:35:26

NASA's Spirit rover photographed a streak of light that was likely part of a Martian meteor shower, scientists announced Wednesday.

The picture is the first of a shooting star above Mars. Further, the flash has been traced back to its parent comet. And now astronomers figure they should be able to forecast Martian meteor showers.

Meteor showers on Earth are typically caused by streams of debris that boil off comets when they pass through the inner solar system on their orbits around the sun. The bits, from the size of sand grains to peas, vaporize as they plunge through the atmosphere.

Skywatchers on Earth are sometimes dazzled by the annual displays of the winter Leonid meteor shower and the summer Perseids, among others.

Similar meteor showers ought to occur on Mars, even though the Red Planet has a very thin atmosphere compared with Earth's.

As predicted ...
On March 7, 2004, Spirit's panoramic camera photographed a bright streak in the sky. Scientists released the image a few days later, but at the time they were not sure if it was a meteor or the Viking 2 orbiter, still circling Mars after its 1970s mission.

Now the scientists have analyzed the path of the object and considered meteor showers that were predicted to have occurred on Mars around that time.

The meteor was likely once a tiny chunk of a comet called Wiseman–Skiff, according to a team led by Franck Selsis of Centre de Recherche Astronomique de Lyon in France.

The analysis is presented in Thursday's issue of the journal Nature.

The result is somewhat speculative, but no other known comet debris stream (or spacecraft) fits the data.

Because of perspective, all meteors from a comet seem to emerge from a single point in the sky, called the radiant, Selsis explained. "On Earth, for instance, Leonids emerge from the constellation Leo, and the Perseids from Perseus."

So the researchers checked to see if the streak was aligned with the theoretical radiant of Comet Wiseman-Skiff.

"We found a very good agreement," Selsis told

The view from Mars
The shooting star was low in the sky and ran across the horizon, creating a relatively long spectacle. If you were on Mars and held a fist at arm's length, resting it on the horizon, the meteor would have soared barely above your fist. In astronomers' terms, it was 14.2 degrees off the horizon.

If you could trace the meteor back and below the horizon, it would have appeared to emanate from the constellation Cepheus, and so the scientists have dubbed the apparent meteor shower the Cepheids.

The streak of light was about 125 to 185 miles (200 to 300 kilometers) away from the rover.

Other researchers have cataloged debris streams from various comets. The streams are made up of many strands, each representing previous passages of the comet. A meteor shower in any given year can vary in intensity depending on the density of the portion of the stream a planet passes through that year. All this knowledge allows astronomers to roughly predict the intensity of future showers.

Upcoming event
Avid meteor watchers might want to begin planning a trip to Mars for 2007.

Image: Rover studies rock
NASA / JPL / Cornell
The Opportunity rover extends its instrument-laden robotic arm to take a close look at "Heat Shield Rock," a meteorite on the Martian surface.
"Our findings indicate that Martian meteor showers may now be predictable events," Selsis said. "Detailed simulations show that we can expect an intense Cepheid shower on Mars, on Dec. 20, 2007."

The word "meteor" is applied to any object that streaks through a planet's atmosphere. If one reaches the ground, it is called a meteorite. Earlier this year, Spirit's twin rover, Opportunity, stumbled upon a basketball-sized rock that turned out to be the first known Mars meteorite.

Ancient asteroid impacts have also carved chunks of rock from Mars, launching them into space. Some of these have arrived at Earth millions of years later, becoming meteors and, in some cases, meteorites. Scientists study these rocks from Mars for clues about the history of the Red Planet.

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Photos: Greatest hits from Mars rovers

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  1. Practice run

    JPL engineers Eric Aguilar, left, and Joe Melko monitor the rover's performance on a sandy slope outside JPL's In-Situ Instrument Lab. (NASA / JPL) Back to slideshow navigation
  2. Blastoff to Mars

    A Delta 2 Heavy rocket lifts off from Cape Canaveral Air Force Station in Florida on July 7, 2003. The rocket launched the Opportunity rover toward Mars. (Boeing via AP) Back to slideshow navigation
  3. Look at that!

    Principal rover scientist Steve Squyres points at Martian snapshots displayed on a big screen at NASA's Jet Propulsion Laboratory, beamed back from the Red Planet just after the Spirit rover's landing on Jan. 3, 2004. NASA Administrator Sean O'Keefe, at right, and mission team members watch as the images are added. (NASA) Back to slideshow navigation
  4. Leaving the nest

    NASA's Spirit rover looks back at its own lander platform early Jan. 15, 2004, just after the mission team sent the robot out for its first spin on Martian soil. Spent air bags are crumpled along the sides of the platform. At the top of the image, the view is mirrored by the bottom of the rover's solar arrays. (NASA / JPL) Back to slideshow navigation
  5. Rover's footprint

    This image, taken by NASA's Opportunity rover and released Jan. 28, 2004, shows the "footprint" left by one of the rover's inflated air bags as the spacecraft bounced to its resting place on Martian soil. The circular region of the flowerlike feature is about the size of a basketball. (NASA / JPL) Back to slideshow navigation
  6. In memoriam

    NASA's Spirit rover took this picture of a plaque commemorating the fallen astronauts of the Columbia shuttle mission, which ended in disaster in February 2003. The 6-inch-wide plaque is mounted on the back of Spirit's high-gain antenna. (NASA) Back to slideshow navigation
  7. RAT bites

    This image, taken by the Opportunity rover on Feb. 28, 2004, shows two holes that allowed scientists to peer into Mars' wet past. The rover's Rock Abrasion Tool, or RAT, drilled the holes (indicated by red circles) into rocks in the region dubbed "El Capitan." An analysis of the drilled rock helped scientists determine that this part of Mars was once drenched in water. (NASA / JPL) Back to slideshow navigation
  8. Bedrock beauty

    A mosaic of images from NASA's Opportunity rover shows the rock region dubbed "El Capitan," which lies within a larger outcrop near the rover's landing site. The outcrop represents the first bedrock ever seen up close on Mars. This image was released March 2, 2004. (NASA / JPL) Back to slideshow navigation
  9. Purple Planet

    A false-color image from the Opportunity rover, released Feb. 9, 2004, accentuates the differences between a green-looking slab of Martian bedrock and orange-looking spheres of rock. Scientists likened the "spherules" to blueberries embedded within and scattered around muffins of bedrock. The spherules are thought to have been created by the percolation of mineral-laden water through the bedrock layers. (NASA / JPL / Cornell) Back to slideshow navigation
  10. A scoop of berries

    This microscopic image, taken at the outcrop region dubbed the "Berry Bowl" near the Opportunity rover's landing site, shows spherelike grains of rock or "blueberries." Of particular interest is the blueberry triplet, which indicates these geologic features grew in pre-existing wet sediments. This image was taken March 11, 2004. (NASA / JPL / Cornell) Back to slideshow navigation
  11. A last look back

    The "Lion King" panorama, captured by the Opportunity rover March 24 and 26, 2004, is a wide-angle view of Eagle Crater and the surrounding plains. Opportunity's landing platform is visible in the center, with tracks leading out of the crater. (NASA / JPL / Cornell ) Back to slideshow navigation
  12. Dunes of Mars

    A false-color view from NASA's Opportunity rover, released Aug. 6, 2004, shows the dune field at the bottom of Endurance Crater. The bluish tint indicates the presence of hematite-containing spherules ("blueberries") that accumulate on the flat surfaces of the crater floor. (NASA /JPL / Cornell ) Back to slideshow navigation
  13. Wide-angle walls

    NASA's Opportunity rover captured this view of "Burns Cliff" within Endurance Crater on Mars during the week of Nov. 13-20, 2004. The rover's solar arrays can be seen at the bottom of this true-color mosaic of 46 images. Because of the wide-angle view, the cliff walls appear to bulge out toward the camera. In reality, the walls form a gently curving, continuous surface. (NASA / JPL) Back to slideshow navigation
  14. Martian clouds

    Clouds add drama to the sky above Endurance Crater in this mosaic of frames taken by the navigation camera on NASA's Opportunity rover on the morning of Nov. 16, 2004. The view spans an arc from east on the left to the southwest on the right. These clouds are part of a band that forms near the equator when Mars is near the part of its orbit that is farthest from the sun. (NASA / JPL) Back to slideshow navigation
  15. Farewell to Endurance

    After spending six months studying rocks inside Endurance Crater, NASA's Opportunity rover climbed out Dec. 12, 2004, and used its front hazard-avoidance camera to look back across the stadium-sized crater from the rim. (NASA / JPL) Back to slideshow navigation
  16. Alien junkyard

    NASA's Mars Exploration Rover Opportunity gained this view of its own heat shield during the rover's 325th martian day (Dec. 22, 2004). The main structure from the successfully used shield is to the far left. Additional fragments of the heat shield lie in the upper center of the image. The heat shield's impact mark is visible just above and to the right of the foreground shadow of Opportunity's camera mast. This view is a mosaic of three images taken with the rover's navigation camera. (NASA / JPL) Back to slideshow navigation
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