The Mars rover Opportunity, NASA’s robotic geologist fitted with an array of tools to search for evidence of water, ended its mission Feb. 13 – three weeks after its 15th anniversary and long past its 90-day warranty.

Over the course of its scientific mission, led by an Earth-bound Cornell professor, Opportunity returned hundreds of thousands of images and reshaped our understanding of Mars’ surface for nearly 14 and 1/2 years. Opportunity’s twin, Spirit, which was challenged by a rocky and rough terrain, officially ended its mission in 2011.

“It’s hard to put the scientific payoff yet into context, since the mission has just come to a close,” said Steve Squyres, Cornell’s James A. Weeks Professor of Physical Sciences and the principal scientific investigator for the Mars Exploration Rovers mission. “Both rovers together revealed that ancient Mars was a very, very different place from modern-day Mars; it was more habitable, more Earthlike than Mars is today.”

Opportunity launched just before midnight July 7, 2003, from Cape Canaveral Air Force Base, Florida. It flew 283 million miles to Mars over six months and 19 days. As the craft landed Jan. 25, 2004, cradled in its cocoon of air bags, it bounced 26 times, traveling 220 yards on the surface, before settling in Eagle Crater on Meridiani Planum – a plains area on the red planet.

Squyres called the landing a “hole in one,” as he and his team moved quickly to conduct science.

Designed to travel 1,100 yards and run for 90 Martian sols (days that are 39 minutes longer than Earth days), the golf-cart size rover had roamed more than 28 miles and logged more than 5,000 sols before a massive dust storm hit last May.

‘Blueberries’

Hours after landing in Eagle Crater, Opportunity relayed panoramic images back to Earth. When Squyres and his Cornell team noted a bedrock outcrop, the rover’s first mission was to examine it.

“The thing about an outcrop is its geologic truth … it is the story of what happened in that place,” said Squyres. “There was a story waiting for us.”

There, the scientific team found “blueberries.”

“When we drove off the lander, we saw something very strange – there was a lot of sand and gravel. Lots of gravel … grains of gravel that looked awfully round,” he said. Using the rover’s microscope, the scientists found the area “littered with an uncountable number of round things … they were scattered everywhere,” he said.

“We had no clue what they were … initially.” Squyres and the team had known that Meridiani Planum likely contained the mineral hematite. They eventually realized that the hard, gravel-like spherules were “concretions” made of hematite and formed in the sedimentary rock when water was present. “It turns out that those blueberries are a strong indicator that this place once contained water,” he said.

Tools and teaching

Cornell graduate and undergraduate students rolled up their sleeves to work on the mission. Along with Squyres, Jim Bell, at the time a Cornell assistant professor of astronomy now at Arizona State University, led the panoramic camera group and a platoon of Cornell students to guide the on-board tools and turn the rover into a mobile geologist.

While NASA’s Jet Propulsion Laboratory, contractors and international partners built the rover’s instruments – such as the Panoramic Camera, or Pancam; the rock abrasion tool, known as the RAT; a microscopic imager; Mössbauer spectrometer; and a Miniature Thermal Emission Spectrometer – Cornellians had helped to define, test and perfect them.

For example, Jascha Sohl-Dickstein ’01 and Jonathan Joseph ’88 created software to give Mars images clarity. Joseph’s software patched together images into a mosaic, while Sohl-Dickstein’s application allowed scientists to conduct spectral analysis in order to understand Mars geology and composition.

Justin Wick ’02 wrote software that superimposed data from two or more different rover instruments, and he developed an application that scheduled the rovers’ daily itineraries.

Heather Arneson ’02, now a NASA aerospace engineer, created instructions and drive/motion sequences for the rovers. As undergraduates, Arneson and Miles Johnson ’02 spent eight months at the Jet Propulsion Laboratory running Pancam under Marslike conditions to calibrate the Pancam’s 16 filters.

Two of the undergraduates who worked on the mission are now members of the Cornell faculty: Alex Hayes ’03, M.Eng. ’03, associate professor of astronomy, built a mock-up of Pancam that aided in color calibration and calculation of the camera’s focal length. Dmitry Savransky ’04, M.Eng. ’05, assistant professor of mechanical and aerospace engineering, took teamwork to heart.

“Working on the Mars Exploration Rovers as an undergraduate demonstrated to me the incredible things that can be accomplished when a group of intensely passionate and dedicated people band together and combine their talents toward a shared goal,” Savransky said. “It convinced me that I needed to go to grad school.”

Hayes said the experience helped set the direction of his career.

“When I was a high school student, I emailed Steve Squyres asking about working on a mission to Mars if I were to come to Cornell as an undergraduate,” recalled Hayes, who was invited to join Squyres’ research group after admission. “The experience I had working on [this project] cemented my decision to work on robotic solar system exploration as a career.”

Hayes added: “The Mars Exploration Rovers mission is better explained as a family rather than a team of colleagues. The connections I made as an undergraduate persist to this day.”

Squyres brought the mission into his classroom and shared fresh science with students – even before he had analyzed it. “This mission was a great teaching tool. It’s easy to think of science as a static body of knowledge that you learn from a textbook. It is not,” he said. “We know more about Mars today than we knew two days ago. For years I’ve started each lecture with, ‘Here’s something that just came down from Mars.’”

Science operations meetings

For most of the mission, Squyres and the Cornell members of the science operations team met in the Space Sciences Building every weekday to help decide the paths and the science of the rovers. “Decisions had to made on a nearly daily basis,” he said. “A rover mission is true exploration.”

You can only plan one day at a time, he explained. “For 14 and 1/2 years we got to be part of the group of people on this planet who decided what to do on that planet. It was an enormous privilege to be part of making decisions on how to use this priceless asset on another world.”

‘An honorable end’

Late last spring, as Opportunity hunkered down in Perseverance Valley on the western rim of Endeavour Crater, a gigantic Martian dust storm began to envelop a large portion of the planet.

NASA’s Mars Reconnaissance Orbiter first detected the storm May 30. On June 10, the Jet Propulsion Laboratory received a transmission from Opportunity, indicating that the craft had enough battery charge then to enable communication. But nothing has been heard since. By June 20, the dust storm blotted out the sun and entirely blanketed Mars. The storm abated in late July, and engineers tried in vain to reach Opportunity through early February 2019. It never responded.

“When I saw that the storm had gone global, I thought this could be it,” said Squyres, explaining that Opportunity was a solar-powered vehicle and needed the sun for energy. “To have Opportunity – designed for 90 days – taken out after fourteen and a half years by one of the most ferocious dust storms to hit the planet in decades, you have got to feel pretty good about it.”

He said: “It was an honorable end, and it came a whole lot later than any of us expected.”

Both rovers gathered a lot of science. “It’s mind boggling to me. If you had told me around the time that we landed that Spirit and Opportunity were going to each accomplish one-quarter or even one-tenth of what they ultimately did, I would have been thrilled,” said Squyres, who praised the engineers at the Jet Propulsion Laboratory for building such durable vehicles. “It’s because of the longevity of the vehicles … that Mars just kept giving us more stuff. The payoff has been immensely greater than anything ever imagined in our wildest dreams.”