NASA's InSight lander is on its way to Mars, after a successful launch on Saturday morning.

The lander was launched by an Atlas V rocket taking off from Vandenberg Air Force Base in California shortly after 4 a.m. local time. It successfully separated from the upper stage more than an hour later.

The lander is in contact with mission control as it heads off on its six-month trip to the Red Planet.

Two CubeSats, or miniature satellites about the size of a briefcase, were launched by the same rocket, basically hitching a ride with the Insight. They are now traveling independently toward Mars, and will attempt to monitor Insight's landing. If successful, they'll be the first interplanetary CubeSats ever deployed by NASA.

As NPR's Joe Palca reported Friday, InSight is a lander — not a rover — meaning it will stay put on Mars as it carries out "an $813.8 million mission to study the interior of the Red Planet":

"Recent Mars missions have snapped pictures of the surface, studied rocks, dug in the dirt and looked for signs that water once flowed on Mars. But as Insight's principal investigator William "Bruce" Banerdt sees it, that's just scratching the surface.

" 'Ninety-nine-point-nine percent of this planet has never been observed before,' Banerdt says. 'And we're going to go and observe it with our seismometer and with our heat flow probe for the very first time.'

"The heat flow probe is basically a 16-foot long thermometer that Insight will pound into the planet to take its temperature.

"InSight's seismometer will measure earthquakes — or more properly, 'Marsquakes.' Quakes on Mars don't happen as frequently as they do on Earth, but they do occur and have been detected by previous Mars landers."

Joe notes that many fundamental facts about the Earth's interior were unknown to scientists as recently as 100 years ago.

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