After a 10-month journey, NASA’s Mars Atmosphere and Volatile EvolutioN spacecraft has reached the Red Planet and slipped into a 35-hour elliptical orbit without a hitch.

“I was on pins and needles and daggers and swords,” said MAVEN principal investigator Bruce Jakosky, a planetary scientist at the University of Colorado at Boulder. “We have one opportunity to get into orbit – so if we have any problem, that’s the end of the mission.”

The mission will test the top of the Red Planet’s thin atmosphere in order to solve an ancient mystery: Where did the rest of the Martian atmosphere go?

Mars is full of signs that stable liquid water once existed on the surface, from geological features resembling lakes and riverbeds to chemical signatures in rocks modified by water. But how long it lasted depends in large part on how long Mars had a thick, protective atmosphere – rather like Earth’s – that could keep the water from freezing or boiling away.

Getting a handle on that time window could help scientists understand whether this wet climate lasted long enough for life to have potentially emerged on Mars.

Understanding the carbon dioxide flow will be key, Jakosky said. Carbon dioxide is a greenhouse gas that can help keep an atmosphere warm, so tracking its disappearance will offer more clues about the climate’s history.

MAVEN joins several other robotic Martian explorers, including NASA’s rovers Curiosity and Opportunity as well as the satellites Odyssey and Mars Reconnaissance Orbiter. The Indian Mars Orbiter Mission is due to arrive Wednesday.

Planets are complex systems, and it’s important to have different spacecraft examining different aspects of Mars’ behavior, Jakosky said.