Update for 4 p.m. ET: NASA's Perseverance rover has successfully touched down on Mars! Read the full story here.
It's landing day for Perseverance and all eyes are on the Red Planet.
The rover spent the last seven months flying the roughly 125-million-mile (202 million kilometers) distance to Mars on a quest to find signs of ancient life. Later today (Feb. 18), the mission will begin a daring "seven minutes of terror"-type descent, and if all goes well, its wheel touchdown will signal the beginning of the most powerful rover yet to roam the Martian surface.
Perseverance will broadcast information back in high-definition 4K, set aside promising rock samples for a sample-return mission and launch the first interplanetary helicopter — all while photographing, laser-targeting and investigating targets in the ancient delta of Jezero Crater.
You can watch the Mars landing live here and on Space.com's homepage, courtesy of NASA, beginning at 2:15 p.m. EST (1915 GMT). The landing is expected at 3:55 p.m. EST (2055 GMT).
Related: How to watch NASA's Perseverance rover land on Mars
Live updates: NASA's Perseverance Mars rover mission
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This mission has been a decade in the making and as such, various officials from NASA expressed a lot of excitement and trepidation in a press conference Wednesday (Feb. 17). Also, understanding Perseverance best comes after putting it in context with the 50 or so years of Mars missions that came before. The groundwork to this life-seeking mission began with exploring signs of water from orbit, landing a few missions, and then sending out the first rovers in the late 1990s and early 2000s.
The first long-running rover missions were Spirit and Opportunity, which landed in 2004 and lasted until about 2010 and 2018, respectively. "[We were] following the water, trying to understand the history of water on Mars and understanding if there were ever a time when there was enough liquid water present on the surface of Mars to support life," Lori Glaze, director of NASA's planetary science division, said in the press conference.
Perseverance rover's Mars landing: Everything you need to know
"That was followed, of course, by Curiosity [in 2012] — where we really took the next step to understand the habitable environments on Mars. We were able to confirm the presence of a lake of liquid water on the surface of Mars that was sustained over a period of time, and also identify the complex organic molecules that would be the building blocks for life.
"We've built on all of that knowledge to prepare ourselves now with the Perseverance rover," Glaze continued, "which is going to take that next step — to really, actually look for those signs of life."
Landing on Mars is the first planetary challenge the Perseverance rover, or "Percy" for short, will face as it whips into the atmosphere. Most Martian landing sites of past missions were wider plains, but Jezero Crater has more interesting terrain — craters, rock fields, sand dunes, a wealth of places to explore.
"All those things also represent landing hazards for the spacecraft," warned Matt Wallace, Perseverance deputy project manager at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California. "So we do have a new hazard avoidance capability we call terrain-relative navigation, which we'll employ for the first time."
In the last minutes before landing, Perseverance will use artificial intelligence to scan for the safest landing site below — and then it will make final adjustments to touch down softly on the surface. The computer-directed landing is a necessity because the light speed between Earth and Mars is too great for somebody to hand-steer the rover remotely, all the way down.
Controllers have not been idle these last few months, however, rather spending the time to make sure Perseverance will stick its crucial landing. Indeed, for about nine years before Perseverance launched, they were already discussing how the last few minutes of the mission would proceed, Wallace said. In more recent weeks, there was lots of practice also, preparation of the various systems.
"Our [pyrotechnic] systems are armed and ready to execute the deployments necessary to execute entry, descent and landing," Wallace said. "We have tested out our engines and our guidance sensors — they are ready to go, and really we just have a few more [planned] interactions with the spacecraft. But if necessary, Perseverance could land itself already, without any more help."
The next step after landing is to start communications with Earth. Perseverance can send back simple "tones" or communications without data attached to it, and an orbiting spacecraft known as Mars Atmospheric and Volatile EvolutioN (MAVEN) can send back a little more data a few hours after landing.
But what is really required for real-time updates is the muscle of the long-running Mars Reconnaissance Orbiter (MRO), a frequent relayer of information from surface spacecraft. MRO recently received a new set of software to relay data from the rover, said Allen Chen, Perseverance's entry, descent, and landing lead, at JPL. The data sent back during landing will be slow at only eight kilobits per second, roughly half the speed of a dial-up Internet connection, but it will be valuable to see how the spacecraft did.
"We'll be able to show you what's going on in real time — and show ourselves as well," Chen said. "We'll be able to see what mode we're in, where we think Perseverance is looking, how fast we're going, how high we are above the ground, even an estimate of how much fuel we have left as well. We hope to use that to assess what's going on and to show everybody else what's going on, as it's happening."
All of MRO's and Perseverance's information will be useful to numerous future landing missions, NASA officials said, allowing spacecraft in years to come to fly and land more precisely. Such information would in fact be useful for any world with an atmosphere, such as the intriguing moon of Saturn, Titan, which has prebiotic chemistry and may help us understand more about the origins of life in the solar system.
The first few weeks after Percy's landing will be intense, as the team temporarily works on "Mars time" (a Martian day or "sol" of 24 hours, 37 minutes) to make the most of the first action-packed weeks on the surface. Data will flow back constantly from the rover to the science team, which will need to interpret what they see and then figure out what to do the next day. Next, that information needs to be coded into the rover and sent to Mars for execution.
"This is a very fast-paced, high-stakes operation. It's kind of a race to get it done. And it also involves literally hundreds of people having to work together seamlessly. I can tell you, this is not what scientists usually do. Scientists do not usually perform under these kinds of circumstances," Ken Farley, Perseverance project scientist at the California Institute of Technology, said at the press conference.
So JPL — as JPL often does — turned to simulation. Farley said the team sent scientists out to the Nevada desert with instruments for a week to simulate rover activities, while the rest of the science team remained at JPL or at home — a necessity given that everyone still needs to largely self-quarantine amid the novel coronavirus pandemic.
"One special skill we've had to pay attention to — and it's different than ever before — is the science team is not going to be shoulder-to-shoulder doing this for the foreseeable future," Farley said. "We are going to be operating remotely. So literally, the science mission is going to be executed from people's living rooms and bedrooms, all around the country and all around the world. It's spectacular that we are able to do that. It's a big challenge and I think we are ready."
Ground images from the rover will be needed to figure out the best and safest pathway forward for exploration. Perseverance's wheels are beefed up compared to the delicate wheels of Curiosity, which got unexpectedly torn up due to tough terrain in its early mission before JPL made driving adaptations. Using images from Perseverance and orbit, the team will look for key scientific targets — "rocks that we think will tell us the most about the geologic history of Jezero Crater," Farley said.
"They are the places where we think there may be evidence for past life on Mars, where we might find biosignatures and places where we are likely to collect samples, so getting onto that trajectory will be something that we do very early in the mission," he added.
"So, I can tell you that the science team is very excited for this transition. And I personally am extremely excited for those first images that are going to come back. They will be fabulous from a scientific point of view and also, a huge milestone after so many years of effort in this mission.
Visit Space.com today for complete coverage of the Perseverance Mars rover's landing on the Red Planet.
Follow Elizabeth Howell on Twitter @howellspace. Follow us on Twitter @Spacedotcom and on Facebook.