NASA spacecraft barreling toward a Mars landing

PASADENA, California—NASA’s Curiosity rover is zooming toward Mars.

With about a day to go until a landing attempt, the space agency says the nuclear-powered rover appears on course.

Tension will be high Sunday night when Curiosity plummets through the thin Martian atmosphere and attempts to set its six wheels down on the surface.

During the “seven minutes of terror” plunge, it will steer itself part of the way and in the final seconds — if all goes as planned — cables will lower the rover to the ground.

This novel, controlled way of landing was necessary because Curiosity is too heavy to bounce to a stop using air bags.

Engineers work on a model of the Mars rover Curiosity at the Spacecraft Assembly Facility at NASA’s Jet Propulsion Laboratory in Pasadena, California, Thursday, Aug. 2, 2012. After traveling 8 1/2 months and 352 million miles, Curiosity will attempt a landing on Mars the night of Aug. 5, 2012. AP PHOTO/DAMIAN DOVARGANES

The $2.5 billion Mars mission is the most high-tech and priciest yet. It will expand beyond previous missions’ search for water.