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The Puff on Mars: Mystery solved

Updated 3 p.m. ET Aug. 10: When a Red Planet rover has 17 cameras at its disposal, it's sure to pick up some weird sights now and then — and such is the case with the "Puff on Mars" that was spotted just after NASA's Curiosity rover landed on Sunday night.

The puff was a mysterious smudge that popped up on images taken by Curiosity's front-facing hazard avoidance cameras. The smudge could be seen in the first round of pictures, but was missing in a later round that was taken 45 minutes later. Was the puff just dirt on the lens? A dust devil that happened to be passing through the field of view when the image was taken? Or was it debris thrown up by an interplanetary crash? The experts at NASA's Jet Propulsion Laboratory now say that last hypothesis is the best one.

Curiosity was delivered to its landing spot on Sunday by a rocket-powered descent stage that came to a near-standstill in midair, lowered the rover to the ground on a set of cables, clipped the cables and then blasted itself out of the area. The mission plan called for the stage to crash-land at a safe distance from the rover.

When scientists checked orbital imagery showing the landing site and its surroundings, they found the dark streaks left behind by the sky crane's crash about a half-mile northwest of the rover — in a direction that was consistent with the puff recorded by the cameras. Was the puff actually the cloud of debris thrown up into the air by the crash? "I don't think you can rule it out," mission manager Mike Watkins said Tuesday.

It may sound like an incredible coincidence that the rover's cameras happened to be pointing in just the right direction at the right time to record the splash from the crash, just 40 seconds after the rover's touchdown. But the puff almost certainly wasn't just a smudge of dirt on the lens cover, because it was picked up by two different cameras, left and right. And the circumstances surrounding the puff match up so well with the crash site that the dust-devil scenario seems much less likely.

Steve Sell, a member of the JPL team that monitored Curiosity's entry, descent and landing, confirmed that view on Friday. He noted that the puff did indeed occur at just the right place and time to match up with the sky crane's impact at 100 miles an hour (160 kilometers per hour). "We're fairly certain that that is the impact plume. ... We expected it to kick up a lot of dust," he told reporters.

The fact that the descent stage kicked up that dust right in front of the rover's cameras was "an amazing coincidence," Sell acknowledged.

Case closed? The puff may still have a whiff of mystery about it, but the best course is to move on and get Curiosity ready to catch the next weird sight. Once the rover's Mastcam system is up and running, it will be able to record high-definition color movies at 5 frames per second. The science team is hoping the cameras will track dust devils on the ground, clouds passing through the sky, and all sorts of other moving targets on Mars. So if there are any Martian smoke monsters out there, like the one on the "Lost" TV series, be on guard: Curiosity will be watching you.

More about Mars:

Heard any good Curiosity conspiracy theories? Keep us posted in a comment below.

Alan Boyle is's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.