At the heart of future space exploration lies the feat of returning humans to the moon. The United States, China, and (within the past year) India have all made clear their intentions for manned moon missions by 2020. The Russians claim 2025. And now, Europe is outlining its plans and calling on industry to help develop lunar projects.

Last year, the European Space Agency (ESA) approved funding for launching a lunar lander between 2017 and 2020. The approval was based on studies that the agency conducted in cooperation with NASA that helped define what returning humans to the moon and building a sustainable long-term human presence there would involve.

The study called for such things as fixed and mobile habitation units with integrated life-support systems, autonomous robotic systems that can prepare for human exploration and work with crews, and power-generation and storage systems to support energy needs. The study also called for building systems that can produce resources from materials on the lunar surface.

ESA and NASA agreed that the Europeans could build a cargo lander to supply resources--food, water, oxygen, fuel, etc.--to astronauts during the construction of a human lunar base. But ESA has its sights set on its own lunar lander and is asking the industrial community (including non-space companies) to provide input on its lunar project through a Request for Information (RFI).

While ESA is making plans for its lunar lander, NASA already has its Constellation Program well under way, and its Lunar Reconnaissance Orbiter, a spacecraft to collect lunar information, is scheduled to launch April 24. China and Japan both launched orbiters in 2007, although China's recently crashed into the lunar surface. Meanwhile, India's lunar orbiter launched in 2008, and Russia is planning a project in the next few years, but the lunar-lander designs for China, India, and Russia are not yet publicly known.

As for when humans will actually reach the moon, the India space agency claims to be planning a manned mission as early as 2015, and Michael Griffin, the former NASA administrator, said prior to his departure that China could attempt a manned circumlunar flight that same year.

Who do you think will be the first to send humans back to the moon?