For the eighth time ever, humanity has achieved one of the toughest tasks in the solar system: landing a spacecraft on Mars.
The InSight lander, operated by NASA and built by scientists in the United States, France and Germany, touched down in the vast, red expanse of Mars' Elysium Planitia just before 3 p.m. Eastern Monday
There it will operate for the next two Earth years, deploying a seismometer, a heat sensor and radio antenna to probe the Red Planet's interior. Scientists hope that InSight will uncover signs of tectonic activity and clues about the planet's past. Those findings could illuminate how Mars became the desolate desert world we see today.
Mission control at the Jet Propulsion Laboratory in Pasadena, California, erupted in laughter, applause, hugs and tears as soon as the lander touched down.
"That was awesome," one woman said, wiping her eyes and clasping her colleague's hand. A few minutes later, a splotchy red and brown image appeared on the control room's main screen - InSight's first photograph from its new home.
It was NASA Administrator Jim Bridenstine's first landing as head of the agency.
"This was an amazing, amazing day," he said at a news conference Monday afternoon. "To be in the room when the data stops and to know how quiet it gets ... and then once the data comes back, the elation."
Principal investigator Bruce Banerdt began his career as an intern at JPL on the Viking mission, the first successful Mars landing. Seeing the initial grainy image from InSight felt like "coming full circle," he said. It was an early glimpse at a place on the brink of being explred.
Through the debris covering its camera's dust cover, InSight captured a small rock (not expected to cause any problems for the science) and the edge of its own foot. Off in the distance, Mars' horizon looms.
"This thing has a lot more to do," said entry, descent and landing systems engineer Rob Grover. "But just getting to the surface of Mars is no mean feat."
The interminable stretch from the moment a spacecraft hits the Martian atmosphere to the second it touches down on the Red Planet's rusty surface is what scientists call "the seven minutes of terror."
More than half of all missions don't make it safely to the surface. Because it takes more than seven minutes for light signals to travel 100 million miles to Earth, scientists have no control over the process. All they can do is program the spacecraft with their best technology and wait.
"Every milestone is something that happened 8 minutes ago," Bridenstine said. "It's already history."
The tension was palpable Monday morning in the control room at JPL, where InSight was built and will be operated. At watch parties around the globe - NASA's headquarters in Washington, the Nasdaq tower in Times Square, the grand hall of the Museum of Sciences and Industry in Paris, a public library in Haines, Alaska, - legs jiggled and fingers were crossed as minutes ticked toward the beginning of entry, descent and landing.
At about 11:47 a.m., engineers received a signal indicating that InSight had entered the Martian atmosphere. The spacecraft plummeted to the planet's surface at a pace of 12,300 mph. Within two minutes, the friction roasted InSight's heat shield to a blistering 2,700 degrees.
Grover released a deep breath: "That's hot."
In another two minutes, a supersonic parachute deployed to help slow down the spacecraft. Radar was powered on.
From there, the most critical descent checklist unfolded at a rapid clip: 15 seconds to separate the heat shield. Ten seconds to deploy the legs. Activate the radar. Jettison the back shell. Fire the retrorockets. Orient for landing.
One of the engineers leaned toward her computer, hands clasped in front of her face, elbows on her desk.
"400 meters," came a voice over the radio at mission control. "300 meters. 80 meters. 30 meters. Constant velocity."
Engineer Kris Bruvold's eyes widened. His mouth opened in an "o." He bounced in his seat.
Bruvold grinned and threw his hands in the air. Others leaped from their chairs.
Grover let out a relieved chuckle: "Wow, this never gets old."
Finally, at 12:01 p.m., scientists heard a tiny X-band radio beep - a signal that InSight is active and functioning on the Red Planet.
"Flawless," Grover said. "Flawless. This is what we really hoped and imagined in our minds eye.
Vice President Mike Pence was among the anxious watchers, Bridenstine said; he called the administrator to congratulate NASA minutes after InSight's successful landing.
The mission's objective is to determine what Mars is made of and how it has changed since it formed more than 4 billion years ago. The results could help solve the mystery of how the Red Planet became the dry, desolate world we know it as today.
Early in its history, Mars may have looked a lot like Earth. Magnetization in ancient rocks suggest it had a global magnetic field like that of Earth, powered by a churning mantle and metallic core. The field would have protected the planet from radiation, allowing it to hold on to an atmosphere much thicker than the one that exists now. This, in turn, likely enabled liquid water to pool on Mars's surface. Images from satellites reveal the outlines of long-gone lakes, deltas and river-carved canyons.
But the last 3 billion years have been a slow-motion disaster for the Red Planet. The dynamo died, the magnetic field faltered, the water evaporated and more than half of the atmosphere was stripped away by solar winds. The InSight mission was designed to find out why.
There is no orbiting spacecraft in the right position around Mars to relay real time information about InSight's entry descent and landing back to Earth. But as InSight makes its precarious descent, NASA hoped to learn about its status via the MarCo satellites - tiny twin experimental spacecraft known as CubeSats that accompanied the lander on its flight to Mars. Each has solar arrays, a color camera and an antenna for relaying communications from the Martian surface back to Earth.
About 10 minutes before landing, the control room at JPL erupted in applause - both MarCo satellites were working.
"That means the team now can watch the data flowing onto their screens," said Grover.
Without MarCo, NASA would have had to wait several hours for the details of InSight's fate. Their success during this mission may provide "a possible model for a new kind of interplanetary communications relay," systems engineer Anne Marinan said in a NASA news release last week.
The two tiny spacecraft will continue in their sun-centered orbit, and the MarCo team is discussing with NASA options for further projects for the mission.
NASA should know whether the lander's solar arrays have deployed by Monday evening, thanks to recordings from the Mars Reconnaissance Orbiter. The agency also will get its first clear images of the spacecraft's landing site - a vast, flat, almost featureless plain near the equator.
"I'm incredibly happy to be in a very safe and boring landing location," said project manager Tom Hoffman.
Unlike Opportunity and Curiosity, the rovers that trundle across Mars in search of interesting rocks, InSight is designed to sit and listen. Using its dome-shaped seismic sensor, scientists hope to detect tiny tremors associated with meteorite impacts, dust stormperhaps s and "marsquakes" generated by the cooling of the planet's interior. As seismic waves ripple through, they will be distorted by changes in the materials they encounter - plumes of molten rock or reservoirs of liquid water - revealing what's under the planet's surface.
InSight's seismometer is so sensitive it can detect tremors smaller than a hydrogen atom. But it also must be robust enough to survive the perilous process of landing. Nothing like it has been deployed on any planet, even Earth.
Designing this instrument, said principal investigator Philippe Lognonné, "was not only a technical adventure, but a human adventure."
InSight also has a drill capable of burrowing 16 feet - deeper than any Mars instrument. From there, it can take Mars's temperature to determine how much heat is still flowing out of the body of the planet. Meanwhile, two antennae will precisely track the lander's location to determine how much Mars wobbles as it orbits the sun.
It will take two to three months for InSight to start conducting science, explained Elizabeth Barrett, science system engineer for the mission.
This is the first time NASA has used a robotic arm to place instruments on the surface of Mars, and the agency wants to be careful. There is no option to send a technician in for repairs if something goes wrong.
"I liken it to playing that claw game at a fairground, but with a very very valuable prize ... and you're doing blindfolded and remotely from 300 million miles away," Barret said.
But the insights eventually gleaned from InSight won't only add to what we know about Mars; they could provide clues to things that happened on Earth billions of years ago. Most records of Earth's early history have been lost to the inexorable churn of plate tectonics, explained Suzanne Smrekar, the mission's deputy principal investigator.
"Mars gives us an opportunity to see the materials, the structure, the chemical reactions that are close to what we see in the interior of Earth, but it's preserved," she said. "It gives us a chance to go back in time."
Bridenstine said Monday that information from InSight may guide a potential crewed mission to Mars by providing information about Mars' water, the risk of asteroid impacts, and resources that could potentially be utilized by human explorers.
"The more we learn, the more we're able to achieve," he said.
This article was written by Sarah Kaplan, a reporter for The Washington Post.