Next Launch:

Can We Rescue the Opportunity Rover?

Amy Thompson
Salvatore La Rosa
April 18, 20194:00 PM UTC (UTC +0)

Fifteen years ago, before Gmail, before Facebook and the iPhone, two identical robots rolled onto the Martian surface.

Together, this dynamic duo brought the red planet to life in a way no previous robotic explorers had.

Opportunity and its twin, Spirit, touched down on opposite sides of Mars in 2004, tasked with a common goal: find evidence of water (and perhaps even life) on the red planet. The golf cart-sized rovers were only expected to last 90 days, but the pair exceeded every conceivable expectation. That is, until 2009. Five years into her mission, Spirit became stuck in a sand trap and later succumbed to the harsh Martian winter, falling silent in 2010. Meanwhile, Opportunity kept on trucking, traveling farther than any vehicle on another planet, and farther than all other Mars rovers combined.

In a record-breaking run on Mars, Opportunity drove more than 28 miles across the perilous Martian surface, identifying some of the first definitive signs that Mars was once a wetter place. As part of her prime mission, Opportunity was expected to conduct a quick survey of the small area surrounding her landing site, but the plucky little rover proved to be an overachiever, uncovering evidence of water straight out of the gate. The rover’s early success eventually led to Opportunity embarking on a planet-trekking expedition. And we all got to take part in her epic journey as the anthropomorphized robot beamed back stunning panoramas of Martian craters and rocks.

Acting as our mobile geologist, Opportunity studied the rocks that humans couldn’t reach. “Geology is a forensic science,” explained the mission’s principal investigator, Steve Squyres of Cornell University. “Something happened at this place on Mars billions of years ago, and we want to know what it was. The clues are in the rocks, [and the] rovers [are] equipped with the tools to uncover those clues.”

Opportunity revolutionized what we know about our neighboring planet. Today, Mars is a cold, dry, desolate world, but that was not always the case. Long ago, it was a hot, violent, steamy place that may have harbored life.

For more than a decade, the Opportunity rover was our eyes on Mars. Unfortunately, those eyes may be closed now for good. On February 13, NASA officially declared its beloved Opportunity rover lost, broadcasting the somber news from the agency’s Jet Propulsion Laboratory in California.

The rover’s fate was most likely sealed several months prior, when a planet-circling dust storm blanketed Mars, blotting out the sun’s light. This storm—the worst on record in the four decades that robots have occupied Mars—raged for months, starving the little rover of the energy it needed to keep its batteries charged. But NASA remained hopeful that after the storm receded, the rover would wake back up. As the months passed and commands went unanswered, that hope started to fade.

Many attempts were made to resuscitate the rover, yet none proved successful. After eight months of silence, agency officials made a tough call—and declared the rover dead. Her final resting place: the slopes of a windswept gully, named Perseverance Valley. A fitting resting place for the rover’s incredible efforts. In the end, it took a whole planet to kill her. That is, unless we can revive her.

In 2015, Ridley Scott captivated audiences around the globe with his adaptation of Andy Weir’s novel, The Martian. In it, a NASA astronaut is stranded on Mars, and must use his wits and magical botany powers to survive. One key tool in his box: the Mars Pathfinder robot. Through some clever engineering, Mark Watney is able to revive the robot and use it to communicate with NASA.

But how do you resuscitate a dead rover?

Pathfinder’s batteries—which provided life-sustaining warmth to its onboard electronics—were designed to last a month. The rover surpassed that milestone, successfully operating for nearly three months on the Martian surface. Repeated charge-discharge cycles may have worn the battery out, ultimately causing it to fail. Once the robot’s innards reached critically low temperatures, vital parts may have cracked and broken, rendering Pathfinder unable to communicate with Earth.

In the movie, after Watney unearths Pathfinder from its dusty Martian tomb, he plugs the lander into a power source and is able to boot it up. However, in reality, NASA engineers believe something inside Pathfinder broke due to extremely low temperatures. So, even if someone was able to plug Pathfinder into a power source, it wouldn’t have been able to turn on.

But Opportunity is a different story.

Last summer, Opportunity hunkered down to wait out one of the worst dust storms in Martian history. As the storm raged on, day looked like night, so the solar-powered robot couldn’t charge its batteries. However, it’s possible the real culprit behind her demise was not the dust storm, but instead a clever feat of engineering—the same trick that kept Opportunity running for so many years.

Not long after Opportunity landed, engineers realized that a heater in her robotic arm was stuck in the on position, draining precious battery life. That spelled bad news for Opportunity; unless a work around was developed, her days were limited to 200 sols. But by essentially disconnecting all of the rover’s systems (except for her internal clock) from the battery each night, engineers were able to extend the rover’s life significantly. That’s mostly because unlike her predecessor, Pathfinder, Opportunity relied on a more advanced, longer-lasting battery: the lithium-ion. At the time of her demise, Opportunity’s batteries still had 85 percent left (that’s after 15 years and over 5000 charge-discharge cycles).

Residual warmth coupled with onboard heaters allowed Opportunity to stay just warm enough that she could survive frigid Martian surface temperatures until the sun came up the next morning. But when the massive storm hit, this life-saving fix may have actually spelled the rover’s demise.  

During the storm, not enough sunlight reached her solar panels, and Opportunity slipped into low-power mode. This left just enough power to run Opportunity’s internal clock, until its batteries could charge again. Only that didn’t happen, and the rover’s internal clock may have stopped keeping accurate time. This meant that Opportunity was burning through her battery instead of going to sleep every night.

“With a loss of power, the clock on the rover gets scrambled, and it wouldn’t know when to deep sleep, so it probably wasn’t sleeping at night when it needed to,” explained John Callas, the Mars Exploration Rover program manager. “And that heater was stuck on, draining away whatever energy the solar arrays were accumulating from the sun to charge those batteries.”

Rover teams and NASA officials waited more than six months after Opportunity’s last message, listening for any inkling that the intrepid explorer might wake up. “You don’t want the scenario where the rover is alive but you just gave up,” explained Mike Seibert former Opportunity Flight Director and Rover Driver.

Can we send a rescue crew?

“It’s not out of the realm of possibilities,” Seibert tells Supercluster.

The first step would be to send a human mission to Mars. Luckily, NASA’s already been scoping out the best possible landing sites for such a mission—and Opportunity’s landing site, Meridiani Planum—is a viable option. It’s close proximity to the Martian equator (which means more tolerable temperatures) and vast plains make it a prime piece of Martian real estate.

One of the biggest challenges to this off-world rescue operation would be to crack open her electronics box. The rovers were designed to withstand the rigors of space travel, and are not going to be easy to break into. So, NASA would need to send a computer-savvy space Macgyver. Opportunity’s batteries are in great shape, so is her camera and many other crucial parts. But some of her delicate circuit boards may need replacing. Luckily, her onboard electronics box resembles a giant desktop computer, making it fairly straightforward to switch out her innards.

Opportunity’s batteries have their own housings, and the circuit boards are tucked inside of a coated aluminum housing called the Rover Electronics Module (REM). This means any future astronauts will need to perform some robotic surgery, opening up the rover in order to access her vital systems. Before that can happen, the rover’s solar array deck must be removed.

“The trick would be the tools necessary to disconnect the camera mast,” Seibert says. But since these should be similar to existing EVA tools, they would presumably be at NASA’s disposal.

Luckily, NASA has a supply of spare rover parts here on Earth that crews could bring with them to Mars. Seibert explains that while there aren’t dedicated flight-ready spares, test facilities at NASA’s Jet Propulsion Laboratory (where Spirit and Opportunity were built) have a full set of rover electronics, including the REM. “Some work may need to be done to make those boards ready for spaceflight,” he says, “but they do exist.”

Assuming all goes well and Opportunity is repaired and reassembled without issue, another big challenge is going to be timing. Opportunity’s onboard clock operates on a different time than the systems here on Earth that control it. Her ground control systems tell time using a 32-bit UNIX time system, while the actual rover relies on a special spacecraft clock. This is because many of the systems that are used to command spacecraft are old. For instance, Opportunity's command stations were purchased prior to launch—around 2002—and since they run on a UNIX system, they are plagued by this clock issue. (Newer stations do not have this problem.)

Both systems tell time by counting up in seconds; however, if you thought converting between time zones was tricky, try converting between Earth time and rover time. Seibert says that this can be a complex, multi-step process. The ground-based UNIX system uses a 32-bit binary number to represent whatever time the computer thinks it is. But when a command is created that requires specific timing, that time needs to be translated to something the spacecraft clock can understand. (If something goes wrong in the conversion process, Opportunity won’t be able to carry out her commands.)

There’s one major issue though: the ground system’s clock has a limited number of seconds it can record. Once it reaches that limit, it essentially rolls over. Remember the Y2K computer kerfuffle?

Welcome to the 2038 nightmare.

This is the same type of scenario, only this time, when the clock hits Tuesday 19 January 2038, it will report a negative date value, which can lead to chaos as Opportunity’s spacecraft clock can only understand positive time.

Currently, there’s not an easy fix for this issue. “To fix this would require recompiling the ground commanding tools for Opportunity to run on a newer 64 bit version of UNIX or coming up with other workarounds,” says Seibert. “In theory commands could be directly edited (hacked) to work correctly but that is risky.”

Thankfully, newer UNIX systems use 64 bits for time, so we won't have a similar issue any time soon. But, that means NASA has less than two decades to organize a human mission to Mars. Currently, the agency doesn’t have the technology required to land more than a metric ton of cargo on Mars. (Human missions require around 20-30 metric tons.) The rocket the agency billed as their next deep space transport is having issues and many question its future. But, luckily for Opportunity, there are other rocket manufacturers.

SpaceX, for instance, has big plans for Mars. The private spaceflight company is in the early stages of building its next-generation rocket: the Starship. According to SpaceX CEO, Elon Musk, the futuristic spacecraft (which is fashioned out of stainless steel) will be capable of ferrying 100 people and massive amounts of cargo to the red planet.

Starship looks like something out of a 1950s science-fiction comic book; the silvery vehicle is expected to stand 348 feet tall—roughly equal to the height of a 35-story building. (As such, it towers well above SpaceX’s flagship Falcon 9 rocket, which stands about 230 feet tall, and the 305-foot Statue of Liberty).

To date, a squatty prototype of the innovative transporter has completed two brief hop tests, proving that one of its Raptor engines—each capable of producing 380,000 pounds of thrust—functions. (The actual flight-ready version of Starship will be powered by 31 of these same engines.) Musk’s goal is to send Starship’s first paying passenger on a trip around the moon in 2023. If successful, crewed missions to Mars will soon follow.

Accounting for potential delays, that means that Opportunity’s best chances of rescue are likely at least a decade away. Nighttime temperatures on Mars can plummet as low as -96° C (-140° F). Her electronics are theoretically only able to withstand -40° C (-40° F), but luckily the little rover has small plutonium-powered heater units onboard for extra warmth.

That heat supply might just be enough to keep her warm a few more years—giving our future Martian explorers a chance to rescue her.

Supercluster is supported by Dropbox, a company committed to supporting creative people and their endeavors.
Amy Thompson
Salvatore La Rosa
April 18, 20194:00 PM UTC (UTC +0)