HOUSTON -

What could be NASA's most difficult landing is just hours away as the science lab "Curiosity " is scheduled to land on Mars at 12:31 a.m. CST Monday.

Curiosity will have just seven minutes to go from 13,000 miles an hour to zero and make a safe landing. NASA called this the "Seven minutes of terror."

Visitors at Space Center Houston will be among the first to know if it landed safely. About 1,000 visitors are expected between 9 p.m. Sunday and 2 a.m. Monday to see the first visual confirmation that the rover landed.

Sixty-million miles away on Earth, we can't control or see what happens in those seven minutes. Radio signals take 14 minutes to travel from Mars to Earth.

"We're about to land a rover that is ten times heavier than Spirit and Opportunity ten times the payload. Pretty incredible feat we're about to attempt," said Doug McCuistion, the Mars Exploration Program Director.

If it all works, Curiosity will start its work finding out if there was once life on Mars.