The arrival of the Curiosity rover on Mars may well be the biggest, boldest extraterrestrial landing for NASA since Apollo 11 settled down on the moon on a summer's night in 1969.
Curiosity is scheduled to land in the Red Planet's Gale Crater late Sunday or very, very early Monday, depending on your Earthbound time zone. Confirmation of the landing should come at about 10:31 p.m. PT Sunday for folks on the U.S. West Coast, or 1:31 a.m. ET Monday for those on the East Coast. The rover will have actually touched down before that, but there's a 14-minute communications lag time for signals traveling the 154 million miles from Mars.
The $2.5 billion Mars Science Laboratory mission has been in its spaceflight phase for about eight months, since a liftoff from the Kennedy Space Center in late November. But the centerpiece of the mission is only just about to begin -- two Earth years of Curiosity roaming some 12 miles up a towering mound of sedimentary rock in Gale Crater known as both Aeolis Mons and Mount Sharp.
The science instruments carried by Curiosity will be looking for, among other things, carbon compounds and signs of whether Mars is, or ever might have been, habitable. The rover's uphill climb will take it through eons of Mars' geological evolution.
"The really cool thing about the Gale stratigraphic succession to me is it's a tour through nearly the entire history of Mars, where we can begin to understand these major changes in the environmental history of the planet," project scientist John Grotzinger said in an interview with CNET.
But first, Curiosity has to survive its landing. Much larger than earlier Mars rovers Spirit and Opportunity -- the 1-ton machine is roughly the size of a very small -- Curiosity posed a significant challenge to the engineers tasked with getting it down through the Martian atmosphere and onto the soil of the Red Planet.
At an altitude of about 7 miles, and about 7 minutes from the surface, a parachute will deploy to slow the spaceship's cruise stage from 13,200 miles per hour, first to 900 mph and eventually to 180 mph. About a mile above the surface, the rocket-powered landing stage will take over, slowing things further to the walking-speed rate of 2 mph. At the very modest altitude of 66 feet, the rover will finally separate out, and this is where things get most interesting -- Curiosity will be lowered the rest of the way to the surface on a bridle slung on three nylon tethers below the descent stage, with an umbilical providing a power and communication connection.
In the final few minutes, a high-definition camera will begin recording video. "It does eight frames per second, high-definition-quality video from the backshell coming off [all the way] to the ground," said project manager Pete Theisinger. "So it's a lot of data, it'll take a long time to get it back. But it should be a tremendous movie when it does."
Update Aug. 5 at 5:04 p.m. PT: NASA tweeted just a little bit ago that the live coverage would start at 8 p.m. PT / 11 p.m. ET.
NASA celebrates Curiosity's touchdown on Mars
Bill Harwood of CNET and CBSNews.com contributed to this report.