Boston ? When scientists wanted to explore what kind of life might exist on Mars, public television’s “NOVA” recorded the building and launch of the rovers sent to the planet.

Now, a year later, the “NOVA” team is back with “Welcome to Mars,” featuring data collected by the robots as they searched for signs that the planet may once have harbored tiny forms of life. The program airs Tuesday at 7 p.m. on PBS.

“I want people to come away from the show with a sense of exploring another planet,” said producer Mark Davis. “What I really try to do is reach other people who don’t have science backgrounds and show them how interesting it can be.”

The scientists who worked on the project faced their share of challenges trying to synchronize their schedules with the robots, mainly because a day on Mars lasts 40 minutes longer than a day on Earth, Davis said.

“You get this kind of Martian jet lag, and I had to deal with that too; and so it was very confusing, especially for the first couple of weeks. It took awhile to grasp what was going on,” Davis said.

The arrival of Spirit (the first of the robots to land late the night of Jan. 3, 2004) brought some tense moments for the crew of scientists at NASA’s Jet Propulsion Laboratory in Pasadena, Calif.

Spirit’s twin — Opportunity — had an easier time when it arrived Jan. 24. It floated gracefully down from space at Meridiani Planum, a flat region about the size of Oklahoma, where it took a close-up photo mosaic showing an impact crater and an imprint of a dry river bed flowing into it — two signs that water once existed, said Steve Squyres, an astronomy professor at Cornell University who is in charge of the rover science team.

When the rovers landed, scientists realized that the territory under exploration was once beneath water. One clue was billions and billions of tiny round balls made mostly of the mineral hematite, an iron oxide, which can only form if water is present, Squyres said.

Originally, the robots were to stay on the planet for 90 days. But they turned out to be more durable than researchers expected. So today the robots are still going strong.