NASA jittery but confident about landing probe on Mars

NASA is due to land a probe on Mars for the first time in more than six years on Monday and begin a mission to explore the planet deep into its core.

The InSight probe is scheduled to begin its final descent just before 3 pm (2000 GMT) on Monday, marking NASA's first Mars landing since the Curiosity rover in August 2012.

NASA scientists admitted Sunday to being "a little bit nervous" about the landing but also said they felt confident it would be a success.

"We recognize that you never take Mars for granted. Mars is hard," Thomas Zurbuchen, a lead administrator at NASA headquarters in Washington, said at a news conference.

Less than half of the Mars missions attempted have been successful, "so we are of course worried," Zurbuchen said.

Tom Hoffman, InSight project manager at the Jet Propulsion Laboratory in Pasadena, California, said he'll let out a lot of pent up excitement when the probe lands.

"I am completely excited and completely nervous all at the same time," Hoffman said at the news conference, warning whoever is sitting near him that he is "totally going to unleash my inner 4-year-old" when the probe lands.

He said he and his team worked for years to think through all the things that could go wrong, but there's still an element of doubt.

"We've done everything we can to make sure we are going to be successful but you never know what's going to happen," he said. "Everything has to go perfectly, and Mars could always throw us a curveball."

InSight was launched in May and has travelled more than 484 million kilometres to reach Mars.

The goal of the mission is to study evidence buried far below the surface after other probes have looked at Mars' canyons, volcanoes, rocks and soil. This mission will be like taking the planet's vital signs in order to discover more about its mantle and core, NASA said at its website.

But first the probe, dubbed InSight, for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport, has to land.

The process is expected to be "seven minutes of terror," Zurbuchen said, reeling off the steps beginning with the capsule shedding its propulsion device, a descend through the planet's atmosphere and deceleration with the help of a parachute and retrorockets.

If all goes well InSight will land in an area called Elysium Planitia, which InSight principal investigator Bruce Banerdt described as sandy, even "boring" location.

"If it were an ice cream, it would be vanilla," Banerdt said.

Location is important because InSight is a three-legged probe that remains wherever it touches down.

Among the instruments on the probe is a seismometer, which will monitor "marsquakes" - seismic waves travelling through the interior structure of the planet. The data collected will reveal information that scientists can use to draw conclusion.

"The signatures of the planet's formation processes can be found only by sensing and studying evidence buried far below the surface," Banerdt said.

Another instrument will burrow several metres into the planet to gauge how much heat is flowing out. The observations will shed light on whether Earth and Mars are made of the same stuff. InSight also is affixed with radios to assess the wobble of Mars' rotation axis, providing information about the planet's core.

The mission launched along with two tiny cubesats that will aim to beam data during the landing. The mini satellites are part of a technology demonstrators designed to show that cubesats can explore interplanetary space.

They are part of NASA's overall effort to publicize the event. Viewers will be able to watch coverage of the landing live on NASA Television, but also at the US space agency's website, social media platforms and at public viewing locations in major US cities.