NASA’s Perseverance rover touched down safely in Jezero Crater on Mars on 18 February, kicking off a new era of exploration on the red planet in which rocks will be collected and returned to Earth for the first time.
Encased in a protective heat shield, Perseverance whizzed through the thin Martian atmosphere and then deployed a parachute to slow itself down. In a final landing manoeuvre, a ‘sky crane’ holding the rover fired its rockets to gently lower the six-wheeled, car-sized Perseverance to the surface.
The rover touched down at 3:55 pm US Eastern time, after a nearly seven-month journey from Earth. First images from the surface, taken through the clear lens caps of its hazard-avoidance cameras, showed a dusty landscape studded with rocks. Perseverance is now sitting on the smooth, dark floor of Jezero Crater, about 2 kilometres southeast of what was once a river delta, when the crater was filled with water. High cliffs — the edges of that ancient delta — are barely visible in the initial images captured by the rover.
The landing went as smoothly as engineers had hoped. "I almost feel like we're in a dream," says Jennifer Trosper, the mission's deputy project manager at the Jet Propulsion Laboratory (JPL) in Pasadena, California. In the coming hours and days, the rover will photograph more of its surroundings and begin testing the scientific instruments it carries.
The mission’s goal is to roll around Jezero Crater and collect rock samples from the river delta and an ancient lake that might hold evidence of past Martian life. Ultimately, the rover will leave those samples at certain spots on the Martian ground where future spacecraft can retrieve them — making Perseverance the first step in a multi-decadal effort to bring Mars rocks to Earth.
Exploring the terrain
Perseverance’s arrival was even more of a nail-biter than other Mars landings, because the rover touched down in a geologically challenging spot. Jezero is full of steep cliffs, large boulders and treacherous sand dunes that the spacecraft needed to miss. Engineers at the JPL, which was where Perseverance was built, developed hazard-avoidance techniques to ensure a safe touchdown. Most notably, as Perseverance descended towards Jezero, it used a downward-pointing camera to quickly photograph the landscape and compare the terrain with a set of maps stored onboard. The spacecraft then steered itself away from hazards, coming to rest on a flat spot in one of the few safe areas. "Everything looks great," says Trosper.
The last rover to reach Mars was NASA’s Curiosity, in 2012. It has been exploring an ancient lake bed in Gale Crater, where it has discovered evidence for a once-habitable environment (although it found no actual evidence of past life on Mars).
Perseverance carries two microphones — the first ever sent to the planet — to listen to Martian sounds, such as wind and the crunch of rover wheels rolling across the surface. In 2018, NASA landed another craft, the InSight probe, some 3,500 kilometres away, but it has a seismometer that instead listens for ‘marsquakes’ shaking the ground. InSight scientists think there is a small chance that the probe could ‘hear’ Perseverance land on Mars, when two large parts of the rover’s landing system hit the surface. But they won’t know whether InSight detected the impact until the morning of 19 February, at the earliest. It would be the first seismic detection of a known impact on another planet and could reveal more information about the Martian interior, because waves such as these can help to map geological features below the surface. “All we can do is wait and hope,” says Benjamin Fernando, a planetary scientist at the University of Oxford, UK, who is involved in the effort.
Images from Perseverance's colour cameras, as well as video taken during its descent, are likely to be released in the coming days as well.
During its first 30 Martian days on the surface, the rover will be busy with checking out its instruments, including unfolding a mast laden with high-definition cameras and photographing the area around the landing site. One instrument will pull in some of the Martian atmosphere and attempt to use the gases it collects to make a few grams of oxygen, as a resource for future human explorers.
In the coming weeks, Perseverance will roll away from its landing site and lower a tiny, 1.8-kilogram helicopter from its belly onto the surface. The helicopter, named Ingenuity, will test the first powered flight on another world. “It will truly be a Wright Brothers moment, but on another planet,” says MiMi Aung, the helicopter’s lead engineer at the JPL.
During Perseverance’s first 3 months on the surface, team scientists and engineers will be working on Mars time, in which a day is nearly 40 minutes longer than an Earth day. That means they will often work through the night, their lives pushed into a sort of permanent jetlag. Working on Mars time, though, allows the team to be more efficient in planning daily operations, after they’ve checked in with the rover at the start of each Martian day.
Perseverance aims to travel quickly and efficiently, journeying at least 15 kilometres across Jezero in one Mars year (which is nearly 2 years on Earth) — the time NASA allotted for the initial mission. It carries 43 tubes for collecting Martian rock and dirt; the goal is to fill and lay down 15 to 20 of them by the end of that first year for future spacecraft to pick up.
The plutonium-powered rover could then roll onto a neighbouring plain to explore other environments that were suitable for ancient life and continue collecting rocks and soil. The earliest any of its samples could be returned to Earth is 2031.
Perseverance, which launched in July 2020, cost US$2.4 billion to build and launch and will cost another $300 million to land and operate during its first year on Mars. It is the third mission to reach the red planet this month — following spacecraft from the United Arab Emirates and China, which are both now in orbit.
The Chinese mission, Tianwen-1, will try to land its own rover on the surface as early as May.