The parachute that helped land the Perseverance spacecraft. Within hours of this image's release, people figured out the message hidden in its pattern. Photo / NASA/JPL-Caltech via New York Times
Engineers hinted they had hidden a code in the parachute that landed the Perseverance rover. Within hours, puzzle enthusiasts cracked it.
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, realised what Chen was saying: The seemingly random pattern on Perseverance's parachute contained a code.
He called his father, Jerome, a software engineer at Google in London, and the two set to solving it.
"We like those kinds of little challenges," Maxence 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.
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," 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, Clark noticed that the chequerboard 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, 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," Wallace recalled. "Just make sure it was appropriate and couldn't be misinterpreted."
The 20-metre-wide parachute consisted of 80 strips of fabric radiating outward from the centre to form a hemisphere-shape canopy, and each strip consisted of four pieces. Clark thus had 320 pieces to work with.
Some of his ideas would have required additional colours, but that could have threatened the parachute's integrity if untested dyes weakened the fabric fibres.
"We were unwilling to go to a cloth that was dyed in a color that we had never used before," 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," 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 had to explain how they lost a US$2.7 billion mission because a parachute engineer had sneaked in a secret message.
But 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 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.
They thought that perhaps the digits could be rearranged into a picture, like the message that scientists broadcast in 1974 from the Arecibo radio telescope in Puerto Rico to tell distant alien civilisations of humans on Earth.
"We couldn't find anything that looked like anything," Maxence Abela said.
They tried breaking up the digits into groups of 8 — a common practice used in computer programming — but that too yielded gibberish.
Then the elder Abela noticed that the digits seemed to fit in groups of 10. "Every 10 bits, there would be three zeros in a row," Maxence Abela said. That, they decided, was not a coincidence.
Still, the resulting numbers did not make sense until they realized they had read the 1s and 0s in the wrong direction, anti-clockwise instead of clockwise. When they wrote down the digits in the opposite order, the 10-digit chunks of binary code translated into small numbers, which could then be assigned to letters. The number 1 corresponded to the letter A, the number 2 was B, 3 was C, 4 was D and so on.
The message on the inner three rings: "DARE MIGHTY THINGS."
"dare mighty things" ! Well done! @NASA @NASAPersevere pic.twitter.com/Di1hkFQApd
— Abela_Paf (@FrenchTech_paf) February 22, 2021
Maxence Abela posted on Twitter his answer at 4:36 p.m. Eastern time, about two hours after Chen had dropped his cryptic hint during the news conference.
This is a credo often cited at Nasa's Jet Propulsion Laboratory in California, which built and operates Perseverance. It comes from The Strenuous Life, a speech by Teddy Roosevelt in 1899: "Far better it is to dare mighty things, to win glorious triumphs, even though chequered by failure, than to take rank with those poor spirits who neither enjoy much nor suffer much, because they live in a gray twilight that knows not victory nor defeat."
There were still some numbers and letters in the fourth ring that neither Abela could make sense of. Those turned out to be the longitude and latitude of the Nasa centre: 34°11'58" N 118°10'31" W.
"If you look in Google Earth, if you type in those coordinates, I think you're about 10 feet from the door of the JPL visitor centre," Clark said.
In the evening, Adam Steltzner, the chief engineer for Perseverance, posted an annotated diagram explaining the solution.
It looks like the internet has cracked the code in something like 6 hours! Oh internet is there anything you can’t do? For those who just want to know: #Mars2020 #CountdownToMars pic.twitter.com/yTJCEnbuLY
— Adam Steltzner (@steltzner) February 23, 2021
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.
Did you all find the easter egg on the deck? The family car sticker with Sojourner, Spirit, Opportunity, Curiosity, Perseverance and Ingenuity! #CountdownToMars #Mars2020 pic.twitter.com/C0GzJPxnPr
— Dennis (@ucidennis) February 22, 2021
A plaque that will be used to calibrate one of the rover's main cameras includes patches of colours, 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.)
Also on Perseverance are three small chips with the names of 10.9 million people stencilled on them, part of Nasa's efforts for the public to participate in its robotic missions. A more solemn addition was an aluminum plate that honours hardships of those affected by the coronavirus pandemic.
The practice of adding fun or solemn pieces to spacecraft is not new. In NASA jargon, it is called "festooning." The two Voyager spacecraft that are now in interstellar space have discs full of images and sounds of Earth. Two earlier Mars rovers, Spirit and Opportunity, had parts made from the wreckage of the World Trade Centre. The New Horizons spacecraft, which flew past Pluto in 2015, carries some of the ashes of Clyde Tombaugh, the astronomer who discovered that world.
On Perseverance, a few more surprises have yet to be revealed.
"There's some things on the front of the vehicle that we'll have a chance to see once we deploy the robot arm," Wallace said. He declined to say what they were or provide hints.
"We're going to let people enjoy the imagery when it comes," he said.
Written by: Kenneth Chang
© 2021 THE NEW YORK TIMES
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