For the Curiosity rover, it's just another day on Mars — but back on Earth, Tuesday was a day to look back at the $2.5 billion mission's first year, including a moment when it looked as if the mission might be lost.

The six-wheeled, car-sized rover passed the one-year mark at 1:32 a.m. ET Tuesday, exactly one Earth year after the Mars Science Laboratory spacecraft executed a so-crazy-it-actually-worked entry, descent and landing sequence that had the rover dangling from a tether beneath a rocket-powered "sky crane."



"We were literally sweating beads and biting fingernails," NASA Administrator Charles Bolden recalled.

Allen Chen, the in-house commentator at NASA's Jet Propulsion Laboratory in Pasadena, Calif., confessed during a Monday recap of the mission that there was a point during the descent when he saw a sensor signal indicating that catastrophic failure of the mission was imminent. The signal suggested that the spacecraft was tumbling as it fell toward Mars, or that the protective heat shield was pointed in the wrong direction, he said.

"That really spiked my blood pressure," he said. Chen decided to wait a few moments before telling anybody else what he saw.



"It turns out that the instrument was fine, we just had a calibration error," he said.

"Thanks, Allen," Pete Theisinger, the mission's project manager, deadpanned during the panel discussion at JPL. "I'm glad you didn't tell us."

Instead of declaring Curiosity's doom, Chen ended up reporting the best news of the night a year ago: "Touchdown confirmed — we're safe on Mars."

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Scoopfuls of discoveries

A year later, Curiosity is still safe on Mars, with scoopfuls of discoveries to its credit. The sky crane's rocket blast scoured out Martian soil to reveal bedrock — a promising sign for the mission ahead. The rover's first expedition took it through an ancient stream bed, revealing new insights about the Red Planet's watery past.

The biggest find was geological evidence that Mars once had an environment that would have been hospitable to life as we know it — not just extremophiles, but the kind of garden-variety bacteria you'd find in a typical earthly stream.



"I think the most extraordinary thing, really, is that we found it all so quickly," said Caltech's John Grotzinger, the mission's project scientist.

The sobering thing is that Curiosity is really just getting started. Its odometer just turned over the first mile (1.6 kilometers) of travel a few days ago, and over the next year it's scheduled to roll roughly five miles (eight kilometers) to get to its main destination, a 3-mile-high (5-kilometer-high) mountain known as Aeolis Mons or Mount Sharp. That's where Curiosity's scientists hope to pin down exactly how long ago Mars was habitable, and perhaps find molecular traces that could have been left behind by ancient life.

Birthday party on Earth

In the midst of Curiosity's trek to Mount Sharp, NASA took more than a moment to mark the anniversary: The party hit its prime on Tuesday with a live video event at NASA Headquarters in Washington. Space agency officials and crew members on the International Space Station reflected on the anniversary — and traced the time line for future missions to Mars and an asteroid.

Those missions include this autumn's launch of the Maven orbiter to Mars, the 2016 launch of NASA's InSight Mars lander, a 2020 Mars rover follow-up, a mission in the 2020s to get up close and personal with a near-Earth asteroid (or at least a piece of the rock), and journeys to Mars and its moons in the 2030s.

Prasun Desai, the acting director of NASA's Strategic Integration and Analysis Office, said completely new technologies will have to be developed over the next two decades. Curiosity proved that NASA could land a 1-ton, car-sized payload on Mars. "What we need to do is land a two-story house when we send humans to Mars," Desai said.

Space station astronaut Karen Nyberg agreed that NASA wasn't yet ready for human missions to the Red Planet — not only because of the potential health risks from radiation and prolonged weightlessness, but also because of the sheer logistics of an extended odyssey to another planet.

"It's a trip that can't be resupplied. Once you're going, you're going," she said. "I think we'll get there eventually, but I think right now there's a lot of work to do."

Nyberg said the International Space Station served as a valuable test bed for future trips to Mars, and Bolden seconded that view. "It is our waypoint to Mars," he said. "And it is, in fact, probably the last outpost of humanity before we find ourselves permanently on Mars, one of these days."

To keep the party spirit alive, look for the Twitter hashtag #1YearOnMars, or follow @MarsCuriosity. And for something completely different, check out the tweets from Curiosity's wisecracking alter-ego, @SarcasticRover.

More about the Curiosity anniversary:

Curiosity's first year on Mars is the subject of this week's "Virtually Speaking Science" talk show, which airs at 8 p.m. ET Wednesday on Blog Talk Radio and in the Exploratorium's auditorium in the Second Life virtual world. Tune in via the Web, join us in Second Life, or listen to the archived podcast anytime by downloading it from Blog Talk Radio or the iTunes archive. Last month's show featured NBC News space analyst James Oberg, talking about the Apollo 11 legacy.

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding +Alan Boyle to your Google+ circles. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.