NASA’s latest mission to Mars lifted off through scattered clouds Monday, setting out on a 10-month voyage to discover what happened to the red planet’s water by literally sniffing its upper atmosphere.

Liftoff of the Lockheed Martin-built Mars Atmosphere and Volatile Evolution (Maven) spacecraft from Launch Complex 41 at Cape Canaveral came at 1:28 p.m. EST, the opening of its 2-hr. launch window. Forecasters had predicted a 40% chance cloud cover would force a scrub, with conditions expected to worsen Tuesday and Wednesday.

The Russian-built RD-180 main stage engine burned for about 250 sec., generating more than 933,000 lb. thrust to send the 5,410-lb. spacecraft on its way to Mars. The Centaur engine in the upper stage fired twice over a 30-min. period for a total of 15 min. to put the probe on its interplanetary trajectory. Fairing separation came at 4 min. 32. sec. after liftoff.

The spacecraft was set to use its low-gain antenna to establish communications with the ground 58 min. into the flight. The twin solar arrays, canted into a “gull wing” shape for stability during “deep dives” into the Martian atmosphere for in-situ measurements, were to unfold after that.

Barring a mishap, with its first-day launch Maven will reach Mars on Sept. 14, 2014, when it is planned to drop into an elliptical orbit that will range between 77.6 mi. and 3,864 mi. above the surface over the one-Earth-year nominal science mission.

That $671 million mission was designed to study the interaction between the planet’s upper atmosphere and the solar wind and other solar energy, which scientists theorize stripped away the thicker, wetter environment that existed until about 1 billion years ago. Eight instruments with nine sensors will map the upper atmosphere’s structure and composition, determine how fast the planet is losing gases to space, analyze the processes making it happen, and take additional measurements that will allow experts to roll back the clock and estimate what the atmosphere was like when liquid water ran on the surface of Mars.

Among the measurements Maven will make is the relative levels of Argon 36 and 38 in the upper atmosphere, for comparison with similar measurements made by the Sample Analysis at Mars instrument inside the Curiosity rover on the surface. The results will hold information about the kinds of gases escaping into space.

Maven Principal Investigator Bruce Jakosky of the University of Colorado’s Laboratory for Atmospheric and Space Physics said the argon isotope comparison probably won’t require direct coordination between the orbiter and the rover, but other science teams likely will collaborate with Maven on gathering simultaneous data.

“The reason we want to do that is that Mars is actually a very complicated system,” he said during a prelaunch briefing Nov. 17. “We’ve gone beyond the ability to look at one part of the planet and understand everything there is to know about it. The atmosphere connects to the upper atmosphere and to the solar wind in loss to space; it connects to the surface and the polar caps and the deep interior, so we need to understand all parts of it, and that requires comparing observations from different spacecraft.”

Europe’s Mars Express orbiter has several instruments relevant to the Maven investigations, and a working group has already been established “to make sure we’re getting the right observations at the right time to be able to do that cross coordination,” Jakosky said. India’s new Mangalyaan Mars orbiter, launched Nov. 5, may also be able to work with Maven, and Jakosky’s team is in touch with the Indian Space Research Organization about possible coordination. Mangalyaan is also due to arrive at Mars in September 2014.

“After we’re both in orbit and taking data, we’ll figure out what coordination we need,” Jakosky said.