When it comes to space travel, it's a simple case of math and … how long you're prepared to sit in a capsule, hurtling through the vacuum. Okay, so the math isn't quite so simple. But when you consider that Mars is on average 225 million kilometers from Earth, and that depending on your mode of transport, it could take you between six and nine months to get there, a three-day trip to the moon looks less daunting.
The average distance to the moon is about 382,500 kilometers. So you could get there and back in a week. Compared to that, you'd have to block out almost two years of your life for a round-trip to Mars - up to nine months to get there, a three month wait for the Red Planet to get as close as it can to Earth, and then those nine months back again. But, hey, we don't have the technology to get back from Mars, so you may as well block out the rest of your life.
On top of that, there's still so much we can learn from the moon, and you may quickly wonder why on Earth we would want to run before we can walk. Indeed, you may ask why we've stopped wondering about the moon and turned all our attentions to Mars.
Fortunately there are so many space programs - through government agencies, like ESA and NASA, and private and commercial initiatives - that we can probably manage to explore both the moon and Mars. But we'll return to the moon long before humans ever populate Mars.
"The moon is fascinating because it's there," said German astronaut Matthias Maurer in a DW interview in February 2017. "Everyone knows it and sees it, and we can learn so much on the moon. […] The moon is a dead body, so we can learn about the history of Earth and how our solar system evolved. These are data that scientists need to accurately predict where in the universe we can find life."
So moon first, Mars second.
The moon could also be a base for further missions - deeper into space. For that to work, we'll have to return and continue what was started in the 1960s with the Lunar Orbiter and Apollo missions.
It's now more than 50 years since we started to get high-resolution images of the moon. Starting in August 1966, Lunar Orbiters 1-3 ran reconnaissance to map the moon and find suitable landing sites. Then, on May 4, 1967, NASA launched Lunar Orbiter 4.
Lunar Orbiter 4 provided hundreds of images at higher resolutions than ground-based telescopes could achieve. There were teething problems with the camera equipment and impacts from micrometeorites and particles from solar flares, but "LO 4" did the job. It covered 99 percent of the near side of the moon, producing about 200 images, and a further 75 percent of the far side. It also provided the first images of the moon's South Pole, which is of special interest to scientists as there is evidence of ice.
All the data went towards preparing the Apollo missions.
Within a year, astronauts Frank Borman, James A. Lovell and William A. Anders took Apollo 8 on the first manned orbit of the moon. Less than a year later, Neil Armstrong, Buzz Aldrin and Michael Collins flew Apollo 11 for that historic first lunar landing.
There were six more Apollo missions, including five landings. But human activity went fairly quiet on the moon after the Soviets' Luna 24 mission in 1976.
What just happened?
There were 62 lunar missions between 1959 and 1976. Then nothing until Japan's Hiten flyby and orbiter in 1990. Since then, there have been just 15 missions run by America, another by Japan, China, India and one by the European Space Agency - that is, the space race to the moon is no longer a thing of two nations.
And it's heating up. In the commercial sector, SpaceX and Blue Origin can boast all they like about tourism to the moon and Mars. But the agencies are gearing up too.
In March, US President Donald Trump signed a new contract with NASA - basically a new law - directing the agency to prepare for manned spaceflight by 2033. NASA already seems set to bring forward the introduction of its "Orion" spacecraft for manned missions. But Trump wants something big - same as President John F. Kennedy when he urged the US to "catch up and overtake" the Soviets in the space race. And it may as well be the moon. When Trump signed the new NASA legislation, it was not without reminding the world about 1969. But it's more likely he wants Mars … with bells on.
The Europeans are firmly intent on landing to the moon. Matthias Maurer is certainly interested, and he may make it there before he gets a chance to ride on the International Space Station.
ESA's Director General Jan Wörner, meanwhile, wants to see a "moon village." His agency is working on using 3D printing to make bricks out of simulated moon dust.
At the same time, scientists in the US are making bricks out of a simulated Martian soil. You could say it's the new "brick race." Either way, both projects make the idea of building habitable structures in space a whole lot more realistic. If we can use materials found in-situ, we won't have to take them with us.
It's all work in progress, of course. The first lot to watch will be China's next unmanned mission to the moon in November. That will be significant in itself - but also because China and ESA may soon collaborate on moon missions or indeed on a lunar base.