A review of landing data confirms that a photo taken by the Mars rover happened to capture
Curiosity's spacecraft crash-landing in the distance, an extraordinary coincidence.
© NASA / August 10, 2012
Images taken by the Curiosity rover on Mars show a plume of dust, left, which had disappeared when another photo was snapped 45 minutes later. Engineers say the plume indicates the crash-landing of the spacecraft that delivered the rover to the Martian surface.
Engineers said Friday that the Curiosity
rover happened to catch a picture of its own ride crash-landing on Mars - a wink-of-an-eye serendipity that some dismissed as a statistical impossibility, but appears to have been confirmed by a thorough review of landing data.
The final seconds of Curiosity
's eight-month-plus journey to Mars called for a spacecraft to lower the rover to the surface using a "sky crane" - three ropes. The ropes were then cut, and the last of the spacecraft, known as the "descent stage," cast itself toward the horizon. It crash-landed, on purpose, about 2,000 feet away.
A low-resolution photograph Curiosity
took seconds after landing Sunday night arrived promptly at La Cañada Flintridge's Jet Propulsion Laboratory
, which is managing the $2.5-billion mission for NASA.
The photograph captured a pyramid-shaped blotch on the horizon. The same photo taken 45 minutes later with the same cameras showed the same view of the Martian landscape, but no blotch.
Die-hard space fans took to the Internet raising the possibility that the blotch was an image of the spacecraft crashing, an extraordinary coincidence considering the potential variables, and the fact that the shutter was open for only 200 milliseconds.
"We expected it to kick up quite a lot of dust," said Steve Sell, a member of Curiosity
's entry, descent and landing team. Still, the chances of photographing the crash-landing were "insane," one engineer said.
On Friday, JPL reported that an examination of the mass of data Curiosity
had sent home regarding its elaborate landing sequence showed that the photo did capture the craft crashing into the surface.
The spacecraft that had deposited the rover on Mars took about 20 seconds to arc across the sky and crash at about 100 mph.
The photo was taken about 40 seconds after landing, but it appears that the tremendous impact sent up a cascade of Martian soil that was still hanging in the air when Curiosity
snapped the photo. That could be due in part to the fact that Mars' gravity is 38% as strong as that on Earth.
Many had dismissed the plume as dirt on the camera lens, but engineers pointed out that the initial photo was taken in stereo, with two side-by-side lenses. Both images picked up the same blotch. That eliminated the possibility that the lens was simply dirty, and confirmed, Sell said, that "the artifact was real."
"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."
Also Friday, engineers offered their most detailed assessment of Curiosity
's landing. The craft, they said, landed roughly 1.5 miles away from its predicted touchdown zone - not bad, given that the site was more than 150 million miles away, and the projected landing zone was an ellipse 12 miles wide.
"We flew this right down the middle," Sell said.
Next up for the rover is a four-day "brain transplant." Engineers will be updating Curiosity
's software, currently primed for its flight stage, to prepare it for its Martian surface operations. The update will add two crucial functions - the ability to use the geochemistry lab's sampling system and to drive.
The update had to wait until the rover landed because its processor, built years ago to withstand the harsh environment of interplanetary space, is limited compared with today's consumer technology, said senior software engineer Ben Cichy.
"My phone has a processor that is 10 times as fast as the processor that's on Curiosity
and has 16 times as much storage as Curiosity
has," Cichy said. "And my phone doesn't have to land anything on Mars."
In the meantime, as the rover goes under the digital knife, many scientists will be taking a break, and getting used to their newfound fame.
"I got recognized in a pizza parlor on Wednesday," said systems engineer Allen Chen, who emceed Sunday's Mars landing. "That was a little weird for me."