When most people think of space exploration, the first things that come to mind are rockets and Michelin man-type space suits. They may eventually think of trucks, but that would be way, way down on the list. Yet trucks have been key to man's space exploration for decades.

Aside from serving as fuel vehicles, getting astronauts where they need to be, and being ready in case of emergencies, two of the most famous trucks are NASA's pair of crawler transporters first used in 1966. They brought the Saturn V rockets to the launch pad and, more recently, carried the space shuttle to its launch pad. To give you an idea of how big the trucks are, each one is 131 feet long and 113 feet wide. The crawler has tank-like tracks instead of wheels and tires, and is powered by two 2750-horse diesel engines. Despite all that power, it only goes about 1 mph-the transporter weighs 6 million pounds and can carry 18 million pounds. Trucks are also becoming key for getting around on other planets. We haven't returned to the moon since the 1970s, but rover technology hasn't stopped. For example, NASA built a six-wheeled concept lunar truck at Johnson Space Center with independent steering for each wheel. Unlike the open-air rovers from the Apollo era, the modern-day rover is being designed with a pressurized cabin where astronauts can live and spend every day in regular clothing, donning a space suit only when going outside. One of the companies working on this is the nonprofit Mars Institute, founded in California in 2002. The institute is doing the rover development and research as part of NASA's Haughton-Mars Project.

The image you see here is of one of the vehicles engineers are examining to determine if it would work as a rover on Mars. Appropriately named Mars-1, this AM General Humvee ambulance was radically modified with tracks replacing the wheels, and the entire area behind the B-pillars was converted into a lab area, living quarters, and storage area for space suits. There are also two ATVs along for the ride. That's right-the Mars Institute is perfecting the ultimate off-roader (can't get much more "off-road" than an uninhabited planet), and it isn't some odd, design-studio creation; it's based on a Humvee. Research for how viable this is for use on Mars or the moon has been going on in northern Canada for about eight years. The engineers chose Devon Island, because it has a rocky, desolate terrain similar to the surface of Mars. It is the world's largest uninhabited island, covering more than 21,000 square miles. Its highest temperature is 50 degrees, and there is only a short time period when it gets that warm.

But the team realized that the most important off-roading rule-never go 'wheeling alone-is even more important on another planet. You can't just call 9-1-1 or activate a personal emergency GPS if something goes wrong in space. So they asked AM General to build a second space Humvee to the exact specs of the first. This one, named Moon-1, is in its second career. It appeared in such films as "The Rock" and "Air Force One." It was trucked from the U.S. to Yellowknife, then transported on a C-130 Hercules to Kugluktuk. From there, a group drove it along the Northwest Passage to Devon Island, over hundreds of miles of sea ice. The only issue was when Moon-1 fell through the ice. They anchored two huge steel bars in thicker ice up ahead and used the winch on the front to get the Humvee back on solid ground.

The engineers hope to do more research with Mars-1 and Moon-1 working in tandem at Devon Island this summer. And as team leader Dr. Pascal Lee explains, "Both Mars-1 and Moon-1 are currently diesel-powered, but pressurized rovers would likely be electro-chemical and powered by fuel cells." There won't be diesels on the moon, but these two incredible Humvees may end up keeping astronauts alive and allow for truly go-anywhere exploration. So when you hear about the space shuttle replacement or future space launches, keep in mind that without trucks like these, we wouldn't be able to explore the surface of other planets.