If all goes according to plan, the arrival of NASA's Perseverance rover on February 18, 2021, will mark the end of an era in Mars exploration.
The first era began in 1964 when
Mariner 4, the first successful Mars spacecraft, flew by the planet and sent back images of a seemingly barren, cratered, Moonlike world. To a public raised on fanciful tales of Mars as harsh but habitable land, the views came as a shock. Subsequent missions painted a more varied, nuanced portrait of the Martian environment, raising hopes for the 1976 Viking missions. Two landers dug into the red soil and tested it for signs of life — but they came up empty. Those results closed out Era One with a disappointing message: Mars is a dead planet.
Over the next two decades, planetary scientists began to realize that the Viking experiments were naive, based on insufficient knowledge about the geology and chemistry of Mars. The second Mars era began in 1996, when NASA's Mars Global Surveyor entered orbit and the little
Sojourner rover began rolling across the surface. The goal this time was to develop a deep understanding of the planet's history and evolution, with an eye toward finding out if life ever took hold there, even if it died out billions of years ago. Over time, spacecraft from India and the European Space Agency (ESA), and now China and the United Arab Emirates, joined the effort.
Perseverance is the culmination of Mars exploration, Era Two. For the first time, a rover will explore the Martian surface not just for local study, but to collect samples for return to Earth. All the power of the world's research laboratories will be unleashed on them. The results of those studies could finally uncover the long-sought signs of alien life, or could greatly strengthen the case that Mars was never the living planet we hoped it was.
Scientific curiosity, international competition, and private explorers like Elon Musk guarantee that Era Three of Mars exploration will happen. But what that era looks like will depend profoundly on what Perseverance finds as it samples the landscape around Jezero crater on Mars. You can watch the landing live (with speed-of-light time delay!) via NASA's
online livestream starting at 2:15PM EST on February 18. After touchdown, at 8PM EST the same day, the National Geographic Channel will offer a deep look at the mission's backstory in a two-hour documentary, Built for Mars: The Perseverance Rover.
Even if the landing unfolds flawlessly, we won't know the true meaning of Perseverance's journey until later this decade, when NASA and ESA mount a mission to return its 15-centimeter-long sample tubes to Earth. I spoke with
Ken Williford, deputy project scientist on Perseverance and one of the voices in Built for Mars, about the mission's goals, along with his greatest hopes (and fears) about what the intrepid robot might find. A lightly edited version of our conversation follows.
Perseverance superficially resembles its predecessor, NASA's Curiosity rover, but I know that appearances are deceiving. What’s fundamentally different about this mission?
Great question. The way we're moving the science forward with Perseverance is that we're directly seeking the signs of ancient life and, as such, directly looking for evidence of life beyond Earth in a way that's more serious than any mission since Viking in the mid 1970s. Or more direct is maybe a better word. That’s not a knock on
Curiosity. I myself worked on that mission and loved it; it was very successful. We're standing on the shoulders of giants, but also taking the next step.
The thing that's so exciting to me as an astrobiologist is to get the chance to be a part of a mission that is directly and explicitly tasked with looking for evidence of life beyond Earth. The key distinction between us and
Viking is that Viking was looking for signs of extant life, organisms that are currently alive or recently deceased, whereas we are doing something very different, looking for signs of ancient life, very ancient life, three to four billion years old.