After a 10-month journey, the Mars Atmosphere and Volatile Evolution (MAVEN) probe is making its final approach to Mars and will begin circling Earth's neighbour after 9:30 pm today (0130 GMT Monday).
MAVEN's findings are expected to help pave the way for a future visit by humans to Mars, perhaps as early as 2030.
MAVEN, an unmanned spacecraft, has travelled 711 million kilometres since it launched late last year.
NASA television coverage of the orbital insertion begins at 9:30 pm (0130 GMT). The process will start with the brief firing of six small thruster engines to steady the spacecraft, NASA said.
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Once MAVEN begins circling Mars, it will enter a six-week phase for tests.
Then, it begins a one-year mission of studying the gases in Mars' upper atmosphere and how it interacts with the sun and solar wind.
Much of MAVEN's year-long mission will be spent circling the planet 3,730 miles above the surface.
However, it will execute five deep dips to a distance of just 78 miles above the Martian landscape to get readings of the atmosphere at various levels.
"These are important questions for understanding the history of Mars, its climate and its potential to support at least microbial life."
NASA has sent several rovers and probes to Mars in recent years. The latest robotic vehicle, Curiosity, is exploring Gale Crater and Mount Sharp, looking for interesting rocks and returning data on whether the Martian environment shows evidence of a past ability to support life.
A trip there would take astronauts farther than they have ever ventured before, and it remains unclear if those first pioneers would be able to return to Earth.