NASA’s Mars Parachute Had a Hidden Code. Meet the People Who Cracked It.

The Four Percent


As NASA’s Perseverance rover fell through the Martian atmosphere last week, a video camera on the spacecraft captured the breakneck deployment of its parachute, which was decorated with splotches of reddish orange and white.

Those splotches were a secret message.

During a news conference Monday, Allen Chen, the engineer in charge of the landing system, narrated what could be seen and learned in the slowed-down video.

He added, cryptically and nonchalantly, that his team hoped to inspire others. “Sometimes we leave messages in our work for others to find for that purpose,” he said. “So we invite you all to give it a shot and show your work.”

Across the Atlantic Ocean, Maxence Abela, a 23-year-old computer science student in Paris, realized what Mr. Chen was saying: The seemingly random pattern on Perseverance’s parachute contained a code.

He called his father, Jerome, a software engineer at Google working in London, and the two set to solving it.

“We like those kinds of little challenges,” Mr. Abela said. “We didn’t think we would be able to solve it, but we would at least try.”

Collaborating via teleconference, they downloaded the video, isolated images showing the fully inflated parachute and started piecing together the bits.

So did others around the world, trading insights on Twitter and forums on Reddit. “It’s just exciting that NASA is putting these little puzzles in their missions,” said Adithya Balaji, a graduate student in computer science at Carnegie Mellon University in Pittsburgh who independently tackled the problem.

Mr. Balaji compared the parachute puzzle to a couple of science fiction movies: “Contact,” where a scientist played by Jodie Foster unravels an alien message, and “The Martian,” where Matt Damon’s character Mark Watney communicates with people back on Earth using a similar code.

“I think that it’s exciting that real life can be sometimes even more exciting than the movies,” Mr. Balaji said.

The person who came up with the idea for embedding a message was Ian Clark, who led development of the parachute. NASA’s previous rover, Curiosity, used the same system when it successfully landed on Mars in 2012. But a failure of a prototype parachute intended for future missions spurred engineers to improve the design.

While watching video of a high-altitude test of the new parachute for Perseverance, Dr. Clark noticed that the checkerboard pattern on the canopy made it difficult to track how individual portions of the parachute unfurled and inflated.

Because Perseverance would be outfitted with video cameras, Dr. Clark wanted a pattern that would be visually distinct. That, in turn, provided an opportunity “to have a little fun with it,” he said.

He asked Matt Wallace, a deputy project manager for the mission, for permission.

“I told them OK,” Mr. Wallace recalled. “Just make sure it was appropriate and couldn’t be misinterpreted.”

The 70-foot-wide parachute consisted of 80 strips of fabric radiating outward from the center to form a hemisphere-shape canopy, and each strip consisted of four pieces. Dr. Clark thus had 320 pieces to work with.

Some of his ideas would have required additional colors, but that could have threatened the parachute’s integrity if untested dyes weakened the fabric fibers.

“We were unwilling to go to a cloth that was dyed in a color that we had never used before,” Mr. Wallace said.

Even a pattern of just orange and white, the two colors of previous parachutes, raised potential issues. “There’s all kinds of second-guessing questions,” Dr. Clark said. “Like could having more white than orange, or vice versa, mean that the parachute was going to warm up differently and maybe that would change its behavior?”

After all, mission managers would have been embarrassed if they had to explain how they lost a $2.7 billion mission because a parachute engineer had sneaked in a secret message.

But Dr. Clark’s analysis showed no ill effects, and the plan went forward. Until this week, only about half a dozen people knew about it.

When computer scientists see something in black and white — or, in this case, orange and white — they think of binary code, the 1s and 0s that are the language of computers. That was the first clue that the puzzle solvers pursued on Monday.

For each orange section on the Perseverance parachute, Maxence Abela and his father wrote down a 1, and for each white section, they assigned a 0. That translated into a long string of 1s and 0s.

The parachute was not the only fun that the builders of the Perseverance rover had.

Eagle-eyed observers spotted a series of drawings that represented the five rovers NASA has sent to Mars, from the small Sojourner in 1997 to Perseverance now.

A plaque that will be used to calibrate one of the rover’s main cameras includes patches of colors, but there are also whimsical drawings that include DNA, a rocket and a dinosaur.

On the edge of the calibration plaque is an inscription: “Are we alone? We came here to look for signs of life, and to collect samples of Mars for study on Earth. To those who follow, we wish a safe journey and the joy of discovery.”

Elsewhere on the rover is a piece of a Martian meteorite that landed on Earth and is now back on its original planet. That is to be used for calibration of SuperCam, an instrument that uses lasers and a camera to identify carbon-based molecules and other compounds in rocks and soil. (Before going back to Mars, the same well-traveled rock made a round-trip visit to the International Space Station.)

“We’re going to let people enjoy the imagery when it comes,” he said.


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