A mysterious photo stirred debate over whether NASA rover captured its own ride crash-landing. Said one scientist: "Something was out there."
Did Curiosity capture the galactic equivalent of the Zapruder film when it landed on Mars? Seconds after the NASA robot's landing Monday, Curiosity squeezed off a handful of fuzzy, black-and-white photographs. One, taken with a device on its rear known as a Hazcam, captured the pebble-strewn ground beneath the rover and one of its wheels -- and a blotch, faint but distinctive, on the horizon.
The images were relayed by a passing satellite. Two hours later, the satellite passed overhead again. This time, Curiosity sent home higher-resolution photos. The blotch was gone.
Space junkies raced onto the Internet with giddy speculation about the difference. Curiosity, the largest spacecraft ever sent to another planet, had just sailed through deep space for almost nine months and more than 350 million miles. It landed on its own, meaning scientists had no control over where it would wind up, what direction it would be pointed in nor when it would snap its first images.
After all of those variables, the space junkies insisted, Curiosity had somehow snapped a photo of its chariot crash-landing a safe distance away, as planned. The camera shutter had been open for 200 milliseconds.
The blotch did look like a billowing plume of some sort, erupting from the horizon. But the image "would be an insane coincidence," one engineer said. Most dismissed the chatter as wild-eyed speculation and a statistical impossibility. It was just dirt on the lens, some said -- maybe a dust devil swirling in the distance.
Yet a pesky fact remained. In the first photo, the blotch is there. "And then it's not," said Sarah Milkovich, a scientist at the Jet Propulsion Laboratory in La Canada Flintridge and a leader of the team responsible for delivering images documenting the mission.
And engineers pointed out that the initial photo was taken in stereo, with two side-by-side lenses. That eliminated the possibility that the lens was simply dirty, and confirmed that "the artifact was real," said Steve Sell, a member of the entry, descent and landing team.
Capturing the 'crime scene'
JPL engineers have since received a new image of the landing zone. With tongue in cheek, it was labeled the "crime scene" photo, because it not only showed Curiosity on the ground, but all of the pieces of spacecraft that the rover had discarded on the way down.
To the southwest was the supersonic parachute that had taken Curiosity out of free-fall, and was then jettisoned so it wouldn't land on top of the rover. To the southeast was the heat shield, which soared to temperatures as high as 3,800 degrees and was then ditched so that Curiosity could turn on its radar to navigate its landing. And to the northwest was the spacecraft that had deposited Curiosity on the surface. The crime scene photo showed that the sky crane had crash-landed about 2,000 feet away -- and in the direction Curiosity's rear was pointed toward when it snapped the first photo.
By Friday, engineers said that a review of landing data showed that Curiosity had indeed captured a picture of its own ride crash-landing -- a blink-of-an-eye serendipity. "We believe we've caught what is the descent stage impacting on the Martian surface," Sell said. "We're fairly certain that is the impact plume."
Justin Maki, who led the team that developed the Hazcams, shorthand for hazard-avoidance cameras, explained how it could have happened. Between the front and rear Hazcams, the cameras covered 240 degrees of the horizon. And the material the sky crane kicked up could have hung in the air for a minute or two, he said -- Mars' gravity is 38 percent as strong as Earth's -- which could have increased the chances of capturing the image. He said, "Something was out there."