"It's kind of like going to Vegas. If you have high odds, you play a number of times, eventually one of them is going to bite you," Barry Goldstein, project manager of NASA's Jet Propulsion Laboratory, said.
Phoenix is the first craft that Nasa aims to land in Mars' high northern latitudes.
"The weather looks ideal for landing," Peter Smith, principal investigator of the University of Arizona, said.
"A dust cloud swept through the target site several days ago, but it did not linger and should not affect the spacecraft," he said.
Nasa has not had a successful powered landing since the twin Viking landers in 1976.
The last time Nasa tried was in 1999 when the Mars Polar lander suffered engine failure and crashed into the south pole.
Phoenix will be closely watched by orbiters hovering overhead that will relay information to Earth.
If successful, Phoenix will join two other spacecraft on Mars' surface - the planetary rovers Spirit and Opportunity - which landed in 2004 and have been exploring opposite sides of the planet's plains.
Unlike the twin rovers, Phoenix is designed to stay in one spot and extend its long robotic arm to dig trenches in the soil.
It has an onboard laboratory to heat the soil and analyse the vapours for traces of organic compounds, an essential ingredient for life.