As one mission ends, another begins on the Red Planet.
This week marks the end of Nasa’s Opportunity rover’s mission, silent since a dust storm eight months ago, yet also the beginning of operations for the Mars InSight lander after it successfully deployed its final instrument. This mix of endings and beginnings is the heart of Mars exploration, where the skills, expertise, engineering, and knowledge gained from one mission lead to the next.
At $400 million each, Nasa’s twin Mars Exploration Rovers (MER) Spirit and Opportunity went from approval to launchpad in just 34 months with a designed lifespan of 90 Maritan days (or sols) covering 1 kilometre of roving with one objective: Follow the water. The pair quickly completed their primary missions of finding evidence for past water on Mars and understanding how what orbiters were seeing from space played out in actual rocks on the surface.
And then they kept going.
When Spirit and Opportunity landed on Mars in January 2004, Tim McGraw was crooning:
“Someday I hope you get the chance To live like you were dying Like tomorrow was a gift And you've got eternity To think about What you'd do with it”
The rovers took the advice seriously, exceeding all possible expectations.
Spirit managed 7.7km over 2,210 sols until it was caught with a sticky wheel in a sand trap as winter descended in 2011. Opportunity was even more intense, travelling 45.16km over 5,111 sols. It broke every distance record for off-world driving, even roving backwards when its wheel motor started to fail.
The rover completed a literal marathon and more, traversing from its hole-in-one at Eagle crater, across Meridiani planum, around the rim of Endeavour crater, and farther out across the plains until where it now rests overlooking Perseverance Valley, unresponsive since a dust storm descended in June 2018. Between them, they took 342,432 raw photos, with Opportunity’s final photo sent back to Earth an ominous darkness abruptly cut off mid-transmission.
“We used these rovers to the utmost of their capability,” says Matt Golombeck, project scientist on MER, co-investigator on InSight, and landing site selection specialist in nearly all Mars missions for the last two decades. “We explored far beyond what anyone could ever conceive that we could have done.”
Each rover cost approximately $14m annually for their operations budget, 0.08 per cent of NASA’s total annual budget and one per cent of the amount allocated to planetary science. In return, Spirit photographed a Martian dust devil for the first time, found evidence for water altering rocks sometime in the past, and even found that Martian dust is rich in magnetite, explaining its magnetism and why it rusts to give the Red Planet its distinctive hue. During its long journey, Opportunity found strange round “blueberries” of hematite, sedimentary rock hinting at a watery past, and even evaporites telling tales of salty lakes long-gone.
More importantly, both rovers sparked even more questions with every discovery they made, influencing the design of the $2.5 billion Mars Curiosity rover launched in 2011 that is currently exploring the planet, the $386m Phoenix lander, and even the most recent arrival, the $828.8m InSight lander that reuses Phoenix’s body type but is tasked with using geophysics to explore the internal structure of Mars. “Each and each mission takes the results of the previous mission,” explains Golombeck.
“[MER] went to find out whether the rocks they had seen from orbit were formed from water, and they were,” says Fred Calef III, JPL’s keeper of the Mars map for Spirit and Opportunity, Curiosity, InSight, and for the under-construction Mars 2020 rover. “That led to the next question: If there's water, could it have been habitable in a past environment? Curiosity took that question and answered it, which led to the next question.”
The two solar-powered rovers weathered annual winter chill and reduced sunlight, run-ins with local dust storms, and even survived global dust storms. But the planet-spanning dust storm that engulfed Opportunity last summer was more intense than any scientists had observed before, and quickly dropped the spacecraft into near-darkness.
This may mark the official end of an era where the Mars Exploration Rovers are finally still and quiet on the surface of Mars, but the lessons learned from them will echo into future exploration of the planet. “MER was the perfect training grounds for learning how to explore other planets,” explains Calef. “It’s a rare opportunity to learn those skills.”
“That experience of driving on another planet for 15 years, investigating rocks and geologic processes, is an incredible legacy that lives on in current missions and future missions well beyond it,” says Calef.
In 2018, as InSight launched in May, Opportunity was silenced by dust in June, and InSight arrived at Mars to land in November, a new voice took over the airwaves as Bebe Rexha topped the US Billboard lists, singing:
“Who knows where this road is supposed to lead We got nothing but time As long as you're right here next to me, everything's gonna be alright If it's meant to be, it'll be, it'll be Baby, just let it be”
Check in after check in after check in was missed by Opportunity even as the dust settled, and ping after ping after ping from Earth when unreturned as new dust storms rolled in. Yet on the other side of the planet, InSight’s operators carefully used its claw arm to lift a seismometer, wind shielding dome, and finally heat flow probe from the spacecraft deck onto the Martian surface without a hitch. While Opportunity’s team ran through every fixable scenario with over a thousand attempts to contact their record-breaking rover to call home for a 15th year on Mars, InSight’s team started breaking a whole new set of records by positioning instruments directly on the surface of Mars for the first time.
The two missions hit milestones on February 12, 2019.
InSight placed its final instrument, marking the end of setup and the start of its commissioning phase when its heat flow probe begins hammering itself into the planet next week. And the Deep Space Network spent one last shift in silence waiting for Opportunity to call home.
Next week, the Opportunity team begins wrapping up and starting end-of-mission reports. At the same time, Mars InSight’s team will direct its heat flow probe to start jackhammering itself into the ground, generating vibrations that will be detected by its seismometer. “We're hoping that we actually use that data to map out our local area,” says Suzanne Smrekar, deputy principal investigator for InSight. “We're hoping that the seismic waves generated by the hammering will travel down to that shallow rock layer [below the lander] and bounce back.”
With the official end of the mission, Opportunity joins its twin Spirit, the Pathfinder lander and its mini-rover Sojourner, the Phoenix lander, and the silent remains of all the spacecraft that disappeared during the tricky journey from Earth to Mars.
Smrekar worked on some of those heartbreaking Mars missions that failed before they even got started. “Exploration means pushing the boundaries and encountering failure,” she says. “You have to pick yourself up and keep going.”
But even as Opportunity finishes, Curiosity roves on, drilling holes and tackling new terrains. InSight’s seismometer is already recording in anticipation of its first marsquake, and if its heat flow probe succeeds in burrowing 5 meters into the planet, soon it will break the previous depth record set by a 22-centimetre deep trench dug by the $1bn Viking 1 in 1976. Here on Earth, the European Space Agency's Rosalind Franklin ExoMars rover and NASA’s Mars 2020 rover prepare to launch next year.
Golombeck argues the rovers and their robotic kin are more than worth their price tag. “For the price of several motion pictures, we can the study questions of almost theological importance: Are we alone in the universe? Will life form anywhere that liquid water is stable? Or are we an accident of the highest order?”
The one true constant on Mars is that with each mission, we learn more about the planet that leads to yet more questions to inspire the next mission, and the one after that, and the one after that. As we say goodbye to the long-lasting Opportunity rover and thank it for what we’ve learned, it’s time to wish good luck to InSight and wonder about what we’ve yet to discover.
“You have to have a long perspective,” says Smrekar.
This article was originally published by WIRED UK
