Seven years of work and a journey of nearly seven months were about to be capped by almost seven minutes of terror as NASA ticked off the final hours to the high-drama landing of its USD 993 million Mars InSight spacecraft on Monday.
Mars InSight's goal is to listen for quakes and tremors as a way to unveil the Red Planet's inner mysteries, how it formed billions of years ago and, by extension, how other rocky planets like Earth took shape.
The unmanned spacecraft is NASA's first to attempt to touch down on Earth's neighboring planet since the Curiosity rover arrived in 2012.
More than half of 43 attempts to reach Mars with rovers, orbiters and probes by space agencies from around the world have failed.
NASA is the only space agency to have made it, and is invested in these robotic missions as a way to prepare for the first Mars-bound human explorers in the 2030s.
"We never take Mars for granted. Mars is hard," said Thomas Zurbuchen, NASA associate administrator for the science mission directorate, on Sunday.
The nail-biting entry, descent and landing phase begins at 11:47 am (1940 GMT) at NASA's Jet Propulsion Laboratory in Pasadena, California, home to mission control for Mars InSight.
A carefully orchestrated sequence -- already fully preprogrammed on board the spacecraft -- takes place over the following several minutes, coined "six and a half minutes of terror."