Seven months after blast-off, NASA's Mars 2020 mission will have to negotiate its shortest and most intense phase on Thursday: the "seven minutes of terror" it takes to slam the brakes and land the Perseverance rover on a narrow target on the planet's surface.

Entry, Descent, and Landing (EDL) begins when the spacecraft carrying Perseverance strikes the Martian atmosphere at nearly 12,500 miles per hour (20,000 kilometers per hour).

It ends around seven minutes later with the rover at rest on the surface.

Touchdown on the Jezero Crater is scheduled for 3:55 pm US eastern time (2055 GMT). Weather conditions so far appear favorable in the Martian northern hemisphere spring, but nothing is taken for granted.

"This is one of the most difficult maneuvers that we do in this business, and almost 50 percent of the spacecraft that had been sent to the surface of Mars have failed," Matt Wallace, the mission's deputy project manager said.

A NASA rover streaked toward a landing on Mars on Thursday in the riskiest step yet in an epic quest to bring back rocks that could answer whether life ever existed on the red planet.

Ground controllers at the space agency's Jet Propulsion Laboratory in Pasadena, California, settled in nervously for the descent of Perseverance to the surface of Mars, long a deathtrap for incoming spacecraft. It takes a nail-biting 11 1/2 minutes for a signal that would confirm success to reach Earth.

The landing of the six-wheeled vehicle would mark the third visit to Mars in just over a week. Two spacecraft from the United Arab Emirates and China swung into orbit around the planet on successive days last week.