Like everything else in the 1960s, NASA's Saturn V rocket set a mark for extreme. At 363 feet tall, with 7.5 million pounds of liftoff thrust, it lifted six moon-bound missions into space. Retired in 1973, it remains the tallest, heaviest, and most powerful rocket our species has ever built. With moon missions on hold, we haven't needed anything close to its capacity. Until now. As governments and private companies race to send astronauts to Mars, bigger is once again better—and necessary. Whose heavy-lifter is the biggest and baddest? Here's how they stack up.

United Launch Alliance's Atlas V

In 2011, United Launch Alliance's Atlas V lifted off with the largest thing that's ever landed on Mars—NASA's one-ton Curiosity rover. In 2020, it'll carry Curiosity's cousin. Having safely launched to Earth orbit and beyond 71 times, the Atlas V is ­ultra reliable.

Maximum Mars payload: 11,000 pounds

Cost to launch: $163 million

China's Long March 5

China has been slow to the space race, but it is catching up fast. Its most powerful rocket to date, Long March 5, will deliver a Chinese space station—plus astronaut inhabitants—into Earth orbit, and send the nation's first rover to Mars by 2020.

Maximum Mars payload: 10,300 pounds

Cost to launch: Unknown

SpaceX's Falcon Heavy

Falcon Heavy, debuting this year, can lift twice as much weight as any current rocket. It may launch a Mars capsule as soon as 2020, followed by crewed missions six years later. If that's the case, SpaceX might beat NASA to putting bootprints in red dust.

Maximum Mars payload: 30,000 pounds

Cost to launch: $90 million

NASA's Space Launch System (SLS)

The first rocket to surpass Saturn V 's strength is slated for takeoff next year. SLS will carry astronauts into lunar orbit a few years later, then bring NASA's first crews to Mars in the 2030s. Or 2040s. It's rocket science, so who knows.

Maximum Mars payload: 90,000 pounds

Cost to launch: $500 million

SpaceX's Interplanetary Transport System (ITS)