Farewell Oppy

Published May 2019. “Science is an emotional affair, it is a team sport and that is what we are celebrating today”.

These were the fitting words of Thomas Zurbuchen, Associate Administrator for the Science Mission Directorate at a NASA press conference on 13th February 2019. In a poignant address, NASA announced that the Mars Exploration Rover, Opportunity, would explore no more following the worst martian dust storm in decades.

In the wake of the news, many took to social media to thank the mission team for their decades of work and to bid farewell to the rover. Twitter trended with the hashtag #ThanksOppy and countless messages and images were shared in dedication to the intrepid, little rover. Opportunity’s demise has evoked a mixture of feelings, both palpable sadness and yet, fierce pride and optimism. 

Even though we know it’s just a machine, we’ve projected our humanity onto and into it through its anthropomorphised design (whether intentionally or incidental), and carry the hopes and ambitions of its mission team family. It’s been a cornerstone in creating a close, bonded community – a positive outcome if we are thinking about human exploration of other worlds. 

The tenacity and dedication of the mission team – and an over-achieving rover has meant that the Mars Exploration Rovers program has been a resounding success, completing the most extensive exploration of another world than any other mission to date and producing definitive evidence that liquid water was once present on Mars.

There is much to celebrate. Opportunity landed on Mars on 24th January 2004 in the Eagle Crater, ready for its 90-sol mission (92.5 Earth days) and no one thought that it would still be here almost 15 years later. Powered by solar arrays, the mission team had expected the panels to be covered by dust before long. They never expected the martian winds to give Opportunity a complimentary cleaning service. 

Together with its twin, Spirit, they uncovered a realm of discoveries and relayed beautiful imagery of Mars worthy of the halls of martian science fiction.

To think that it almost never happened. One of the best anecdotes I came across, was of the team’s worry that Opportunity carried the same software glitch that had caused Spirit to malfunction shortly after landing on Mars. With Opportunity already in space, the team sent a software update while the rover was in transit and prayed it would be enough. It was.

One of the mission goals for both of the geologist rovers concerned collecting evidence of a martian environment where water had been stable and that was once hospitable to life. 

Within weeks of landing in the Meridiani Planum region, Opportunity showed us that this region had once been wet, confirming theories that it may have hosted a body of water. Within a month, it sent back its infamous images of small spherical balls of mineral hematite, which typically form in water containing iron, and will forever be nicknamed ‘blueberries’.  Within a decade it had outlived Spirit, (which fell silent in 2011), became the longest operational rover on Mars, and found further tell-tale signs of water when it discovered veins of mineral gypsum (a hydrated calcium sulfate) in the rocks surrounding the rim of the Endeavour Crater. 

You’d think that these were enough accomplishments for one rover. But no, Opportunity kept on. In its last 5 years, it reached the marathon-distance milestone – the mission team even celebrated by naming a region “Marathon Valley” and visited over 100 impact craters. In 2013 it made, quite possibly, its greatest scientific discovery: clay minerals found near the Endurance Crater, that would have formed in neutral-PH water – basically the kind of water that comes out of our taps. 

Both rovers had other mission goals too, focussed on studying the climate and geology. Not only did this contribute further supporting evidence of water but also supported a fourth mission goal: preparing for human exploration.

As it traversed the surface of Mars, Opportunity surveyed the martian environment, its atmosphere, its craters, its hazards, allowing us to paint a picture of what martian life might be like. 

The science delivered really is astounding, and undoubtedly Opportunity takes its place among robotic greats like Cassini. Although luck played its part, much of Opportunity’s endurance of the harsh environment was down to the ingenious mission engineers.

The team made sure the rover was sturdy (a six-wheel design to keep its weight evenly spread and prevent it from toppling over on steep inclines) and durable (aluminium and titanium mobility systems) to overcome the countless challenges presented by the harsh terrain. But they didn’t stop once the rover was off the ground. As one NASA post explains, often the engineers would drive the rover backward in order to extend the front wheels’ life. At another point, the team devised a way to shimmy Opportunity out of a soft-sand dune, where it had been stuck for several weeks. 

The climate was equally unforgiving at times. Swinging temperatures meant that Opportunity’s solar panels were constantly tilted towards the sun so that the rover could continue to work in martian winter.  

In July 2007, Opportunity also survived a month-long dust storm powering down until the skies cleared. It was touch and go, as the temperature of the electronics dropped, concerns arose that the rover would deplete its remaining power to stay warm. Seasonal winds helped to blow the dust off the solar panels and after two-nail biting months, Opportunity was back at work. 

In the end, what luck the planet had bestowed on Opportunity, it took away. A severe dust storm in June 2018 blotted the martian skies, preventing Opportunity from recharging its batteries. Hunkered down in a region known as the Perseverance Valley, its final message was a status report indicating dark skies and low power. The rover’s fate hung precariously in the balance.

Back on Earth, astronomers shared Opportunity’s misery. The dust storm scuppered clear observations of Mars’ surface features during the red planet’s most promising opposition and perigee since 2003, both of which occurred within days of each other in July 2018. By September the martian skies had cleared enough for the mission team to send wake-up calls to Opportunity. This time, however, Opportunity did not pick up.

Prepare your hankies for NASA’s final farewell message. The mission team sent over a thousand recovery messages, initially including cheerful songs such as Wham’s ‘Wake me up before you go-go’. After months of silence, on 12th February 2019, NASA sent its final wake up song, Billie Holiday’s ‘I’ll Be Seeing You’, an emotional surrender of their beloved rover to the red planet.

Opportunity will forever remain at Perseverance Valley. It is a well-deserved resting spot for the rover that redefined our understanding of Mars. John Callas, the project manager for Opportunity said, “Fifteen years on the surface of Mars is testament not only to a magnificent machine of exploration but the dedicated and talented team behind it that has allowed us to expand our discovery space of the Red Planet.”

The current world climate we live in is full of challenges that at times can lead us to question our humanity; but it is moments like this that demonstrate our greatest potential, our limitless reach if we dream and if we can find it in ourselves to imprint our heart and soul into a robot.

Farewell Oppy, and thank you. 

This feature article was published in Popular Astronomy, May 2019 issue.