One of the most complicated missions ever attempted by NASA, the landing of the one-ton rover Curiosity inside a crater on Mars after a 500 million kilometer journey, has apparently gone without a hitch.Curiosity landed at 1:32 a.m. EDT and it wasn't long before the first pictures arrived, including one of the Martian surface framed by Curiosity's wheel.At a post-landing news conference, the scientists in charge of the program were welcomed like rock stars, and could barely contain their excitement. (You can watch a video of the event on YouTube.)"So that rocked. Seriously. Was that cool or what?" said Richard Cook, Deputy Project Manager, Mars Science LaboratoryThe jubilation at the landing capped a tense evening as the craft, as big as a car, hurtled towards Mars at almost 6,000 meters per second. A parachute slowed it down about 11 kilometers above the surface and then at 20 meters above the ground a brand new landing procedure, a rocket-propelled sky crane, lowered Curiosity onto Mars.None of this was controlled in real time. A 14-minute communications delay meant it all had to be programmed in advance, with no room for error. Had anything gone even slightly wrong, Curiosity would have smashed into the planet and the $2.5 billion mission would have been a complete failure.NASA Administrator Charles Bolden said: "Nothing in robotic planetary exploration is harder, more technically challenging, or as risky as landing on the surface of Mars, and I know most of you are saying 'How can he be saying that? It just looked so easy.' Trust me. Historically, counting all the missions by all countries, the odds of success are about 40%. The recent U.S. record is better with now six successful missions including now four landing."Now begins a projected two-year mission. Planetary Scientist Chris McKay at NASA Ames Research Center in northern California will use Curiosity to look for organic compounds in the Martian dirt."There're two important advances that I think Curiosity will bring to scientists like me," said McKay. "One is the ability to go up to different outcrops and different soil types and sample them. Dig in a pick something up and analyze it. And the other is the instruments themselves are much more sophisticated than previous examples. In the case of the instrument I'm involved in, the organic analyzer, this instrument has modes that the previous organic instrument on Viking did not have. And I think these modes will allow us to detect definitively, on Mars, the presence of organics. So I'm hoping that in maybe a couple of months, I can stand before you again and say yes, we know there are organics on Mars, here's their concentration, here's the type of organics that are there. That's very exciting. It's the first step towards advancing our knowledge of whether there was life on Mars and could we find evidence of it."With a team of 300 scientists working on the program, NASA hopes that's just one of many findings to come.