For planetary scientists, it’s white-knuckle time.

At 7:31 tonight, NASA will attempt to land its latest Mars rover on the planet’s surface, as complex a procedure as the space agency has ever endeavored.

At stake is not only the $2.5 billion robot and the extensive labor that put the plan into action, but years of potential research projects at the University of Hawaii and other institutions.

The rover, dubbed Curiosity, is a nuclear-powered, SUV-sized vehicle developed to search for signs of former bacterial life on the Red Planet, and gather information on its geology and climate ahead of a future manned mission. It is far more sophisticated than the Spirit and Opportunity rovers that landed in 2004.

The rover’s intended landing site, Gale Crater, is a particularly promising spot for that search because it might have once had water in it, scientists say. In the middle of the crater is a 3.5-mile-high mountain rich with sediment.

"If it works, it will be absolutely incredible as far as what it would do for UH in terms of creating new opportunities, not only for science but bringing in new graduate students," Peter Mouginis-Mark, director of the UH Institute of Geophysics and Planetology, said in a phone interview Thursday. "There will almost certainly be a call to the (scientific) community, and there are several UH faculty members who would be very appropriate for different instrument teams, whether it is a camera or spectrometer or geographical mapping."

But first Curiosity has to get down to the surface.

Scientists around the world — including at the Pacific Ocean Science and Technology building at UH-Manoa — will be on the edge of their seats, if they can bear to sit at all.

Curiosity, housed in a spacecraft called the Mars Science Laboratory, was launched from Cape Canaveral, Fla., on Nov. 26 and has been approaching Mars at a speed of 8,000 mph. As of 8 a.m. today, it was due to be about 96,000 miles from the planet.

Weighing about a ton, Curiosity is too heavy to land using airbag cushions, as did the previous rovers.

So as it approaches the planet, a so-called aeroshell containing Curiosity will separate from the spacecraft and fire rockets to orient its heat shield to descend through the atmosphere.

When its speed has dropped to about 1,500 feet per second, it will pop a parachute.

At just over a mile up and traveling at 220 mph, Curiosity and a rocket-propelled "sky crane" will separate from the aeroshell.

"The sky crane comes into operation about 400 meters (1,040 feet) above the surface of Mars," Mouginis-Mark said. "It has a number of rocket jets that will slow the rover down to a relatively safe landing speed and then lower the rover down to the surface on a series of cables. Then, when it reaches the ground, you have to detach the cables and then the sky crane flies off so the rover doesn’t get entangled in the landing gear."

Mouginis-Mark called the landing sequence "particularly gutsy."

But he added, "The engineers say they understand this quite well and have relatively high confidence that it will work. It’s cutting-edge technology. It is American technology at its finest."

If the landing is successful, Curiosity should send back its first pictures within an hour or so, he said.

The only UH researcher likely more anxious during the descent than Mouginis-Mark is Scott Rowland, a volcanologist who worked on one of Curiosity’s instruments, the Mars Hand Lens Imager, which will take high-resolution photos of rocks and dirt at the landing site.