We are just two decades apart from the moment humans will set foot on the Moon once more, scientists attending NASA’s Lunar Science Conference suggested, in anticipation of future opportunities for lunar exploration.

The goal is to create a permanent presence on the Moon, and perhaps create premises for permanent missions on Mars as well: “We’re going back, and thus time we’re going to stay,” said S. Pete Worden, director of NASA/Ames, as quoted by San Jose Mercury News.

Apollo 11 was the first and only manned mission on the Moon and represents a historical moment that hasn’t been repeated since. However, this time, ambitions are much higher, as researchers plan longer human explorations on the Moon.

Things are a lot more difficult than they sound, and if robot missions can do well, it will be much harder for humans, as they will have to deal with much weaker gravity. There are still a lot of questions to be answered before another step on the moon is taken.

In the meantime, U.S. isn’t the only one working on future man missions, as the Europeans, Russia and China are developing projects of their own: “Certainly it is possible that if China wants to put people on the Moon and f it wishes to do so before the United States, it certainly can,” NASA administrator Michael Griffin told BBC last week.

Until then, the near future will bring robotic missions to the Moon, including those encouraged by Google’s Lunar X PRIZE. Google promised $30 million in prizes for the teams managing to land a robotic rover on the Moon by 2014.

Google’s initiative was set to beat NASA’s plans to return to the moon by at least 6 years…at least in terms of actually reaching the moon. NASA said it will send astronauts to the moon by 2020. Even without a human crew, the teams competing in Lunar X PRIZE need to prepare their robotic missions for temperatures of 250 degrees below zero.