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. Several hours later it sent a clearer image.
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.
Through the debris covering its camera's dust cover, InSight captured a small rock and the edge of its own foot. Off in the distance, Mars' horizon looms.
"I'm incredibly happy to be in a very safe and boring landing location," said project manager Tom Hoffman.
"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 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 160 million km to Earth, scientists have no control over the process. All they can do is programme the spacecraft with their best technology and wait. "Every milestone is something that happened 8 minutes ago," Nasa Administrator Jim Bridenstine said. "It's already history."
Engineers received a signal indicating that InSight had entered the Martian atmosphere. The spacecraft plummeted to the planet's surface at a pace of 19,800 km/h. Within two minutes, the friction roasted InSight's heat shield.
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 metres," came a voice over the radio at mission control. "300m. 80m. 30m. Constant velocity." Engineer Kris Bruvold's eyes widened. His mouth opened in an "o." He bounced in his seat.
"Touchdown confirmed." Bruvold grinned and threw his hands in the air. Others leaped from their chairs.
Finally, 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."
