In April, when SpaceX announced an ambitious mission to land an uncrewed Dragon spacecraft on Mars by 2018, one of the biggest questions was how much the private rocket company would spend on this venture. Now we have a ballpark estimate: $300 million.

During a meeting of NASA's Advisory Council Tuesday, one of the agency's deputy associate administrators, Jim Reuter, provided an overview of NASA’s agreement with SpaceX, SpaceNews reports. NASA estimated that it would spend about $32 million on the mission, with SpaceX spending about 10 times as much.

The agency and the company have a Space Act agreement that bars the transfer of funds, but the agreement will allow NASA to assist SpaceX with some technical advice. NASA can also gather critical information about the Martian atmosphere and get tips on how to slow a large spacecraft descending toward the planet's surface. It's also likely that NASA, with its assets in orbit around Mars, will help facilitate communication between the Red Dragon and Earth.

SpaceX has not said how much it will spend on Red Dragon, but it views sending the six-ton spacecraft to the Martian surface as a precursor to its plans to land humans on the surface in the 2020s—and to eventually colonize the planet. The company's chief executive, Elon Musk, is expected to release more details about his Mars plans at an international conference in Mexico this September.

The Red Dragon mission will be a big first step. With a thin atmosphere, Mars doesn't provide a very effective medium for aerobraking. A spacecraft must attain a great velocity (and therefore invest a lot of energy) to reach Mars in six to nine months, and once it's there, it must then somehow shed that energy and slow down. Musk believes the upgraded Dragon 2 spacecraft will be able to use its eight SuperDraco engines to slow its velocity and then land on Mars in a powered descent, similar to the way the Apollo Lunar Module landed on the moon.

None of the spacecraft NASA has successfully flown to the surface of Mars have been nearly so large as Dragon, and no other country has ever soft landed a spacecraft on Mars that survived more than a handful of seconds. Even so, if NASA or SpaceX wants to send human missions to Mars, they must learn how to land payloads much heavier than Dragon, so this mission represents an interim step toward 10- and 20-ton payloads.

SpaceX has acknowledged that it must meet an aggressive schedule for a 2018 Mars launch, not the least of which is completing development of its Falcon Heavy rocket. If SpaceX can't meet the 2018 launch window, it will be forced to wait until 2020 when the planets again fall into a favorable alignment.

It may be an audacious plan, but an engineer familiar with the company's plans and efforts to land in the thin Martian atmosphere told Ars in April that the project is no lark. "It’s something they’ve been working on for a while," said Bobby Braun, NASA's former chief technologist. "Don't get me wrong, it is certainly a risky proposition. But you've got to give them credit. They've been testing a lot of these Mars landing technologies already here on Earth. That certainly improves their chances of success."