LIVE NOW: Mars Rover's High-Wire Landing

When it comes to visitors, Mars can be a reclusive, get-off-of-my-lawn world. Of 13 previous attempts to land space probes on the Red Planet over the past four decades, nearly half failed or immediately lost contact.

Those odds are enough to make tonight's scheduled landing of NASA's new rover, Curiosity, a tense, hold-your-breath moment. But the space agency's plan to use a hovering, rocket-powered "sky crane" to lower the $2.5 billion, nuclear-powered robot 60 feet or so to the Martian surface almost guarantees it will be a suspenseful night at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

Just to complicate things, the rover's rapid-fire descent and landing is entirely automated. With more than 150 million miles separating Earth and Mars, round-trip communications between Curiosity and its far-off human overseers would take nearly half an hour.

"Curiosity is on its own through all this," says NPR science correspondent Joe Palca, who is monitoring the Mars mission in Pasadena. "Earth is too far away help if things go wrong."

The communications lag is also why we won't know whether the rover has successfully landed until 1:31 a.m. ET on Monday, even though landfall is actually scheduled for 14 minutes earlier, at 1:17 a.m. ET. (That's 10:17 p.m. PT on Sunday for the mission controllers in Pasadena.)

NASA TV is streaming live video tonight. We'll post updates below as the landing time approaches.

Update at 1:15 a.m. ET.

Mission control just got word that Curiosity successfully separated from the cruise stage that has carried the rover since its launch from the Cape Canaveral Air Force Station in Florida ? 36 weeks and more than 150 million miles ago.

Now things begin to move fast. As science correspondent Joe Palca told our Newscast unit, "A lot has to go right for the rover. . . to land safely":

"A heat shield has to slow the spacecraft from 13,000 mph to about 800 mph. Then a giant supersonic parachute has to unfurl properly to slow the rover further to about 200 mph. Then onboard radar has to detect the surface, and rocket engines aboard a kind of jet pack have to fire, slowing Curiosity to a crawl. Finally, a bridle has to lower the rover from the jet pack to the surface."

Easy enough, right? A NASA video calls the whole chain of events "seven minutes of terror." You'll find that and a gallery of artist renderings depicting key moments in Curiosity's descent and landing in Joe's profile of one of the engineers behind this intricate plan.

On Sunday's All Things Considered, Joe also talked with Richard Kornfeld, a senior engineer on the landing team, about the 14-minute delay before transmissions reach Earth. For people like Kornfeld, this has to make the Olympics coverage feel real-time.

Update at 1 a.m. ET. The 'Bermuda Triangle' Of Space?

Not that we want to jinx Curiosity, but it's worth a moment before the descent begins to go back through Mars' well-earned reputation as dangerous destination for space probes.

We mentioned that 7 of the 13 previous attempts to reach the Martian surface were successful. The first, the Soviet Union's Mars 3 lander in 1971, arrived during a sandstorm and only send back one partial, fuzzy image from communication was lost seconds later.

Of the six failures, the landing vehicles crashed, lost contact on the way down or on the ground, missed Mars entirely, or never made it out of Earth orbit. The most recent losses were the European Space Agency's Beagle 2 in 2003 and the U.S. Polar Lander in 1999. The others were led by the Soviet Union or Russia.

That said, the overall U.S. track record with Mars landings has been a solid six-for-seven, including:

• The twin Viking 1 and 2 landers of 1976
• The Pathfinder lander and its small Sojourner rover in 1997
• The far more sophisticated Spirit and Opportunity rovers, which landed in 2004 (one of which, Opportunity, continues to return data)
• And the 2008 Phoenix lander, which confirmed the presence of water-ice beneath the arctic plains near the planet's north pole.

Update at 12:20 a.m. ET. The Landing Site

Curiosity's destination is Gale Crater, where the six-wheeled rover is expected to spend at least two years looking for signs of water or possibly a long-gone lake.

Samuel Kounaves, a chemistry professor at Tufts University, talked to NPR's Joe Palca and science writer Jessica Stoller-Conrad about the mission's scientific goals. The rover "is not going to be looking for life directly, but it's going to be looking for past habitability," Kounaves told them. "We're looking to see if the elements required for life are there."

Gale Crater is nearly 100 miles across. Curiosity will try to land in a relatively flat area between the crater's rim and the steep slopes of Mount Sharp. The landing zone ? 4 miles wide and 12 miles long ? was narrowed recently to try to place Curiosity closer to the three-mile-high mountain, where scientists hope the rover will uncover layers of Martian history.

Mount Sharp was named for Robert P. Sharp, an influential planetary geologist who died in 2004.

Source: http://www.npr.org/blogs/thetwo-way/2012/08/05/158178277/live-now-mars-rovers-high-wire-landing?ft=1&f=1007

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