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We've all heard how US space agency NASA was going to put humans on Mars in the 2030s.
NASA named the mission "Journey to Mars" and put a detailed explanation about it on its official website.
NASA's explanation of its Mars mission on the agency's official website.
But the agency's chief of human spaceflight acknowledged on Wednesday that it did not have enough money to carry it out as sch.
"I can't put a date on humans on Mars, and the reason really is the other piece is, at the budget levels we described, this roughly 2 percent increase, we don't have the surface systems available for Mars," said William H. Gerstenmaier during a meeting of the American Institute for Aeronautics and Astronautics, or AIAA.
William H. Gerstenmaier, chief of human spaceflight at NASA, explains the challenges to conduct a Mars mission at an AIAA meeting in Georgia, US on July 12, 2017.
Gerstenmaier did not provide a new timetable for the mission, and said "entry, descent and landing is a huge challenge for us for Mars."
Is there a back-up plan?
Instead of talking more about the trip to Mars, Gerstenmaier mentioned the possibility of another lunar mission.
Americans have been there before, so why are they heading for Moon again?
The Apollo 11 Contingency Lunar Sample Return Bag, used by Neil Armstrong on Apollo 11 to bring back the very first pieces of the moon ever collected, is displayed during a media preview for Space Exploration auction in New York on July 13, 2017
"If we find out there's water on the Moon, and we want to do more extensive operations on the Moon to go explore that, we have the ability," Gerstenmaier explained.
Water is critical for lifeforms on Earth, like humans, to survive. So while this plan sounds solid, it's not as attractive as the Journey to Mars, which NASA said will enable humans to "get, land and live" on the planet.
Competitors in the way
Another reason why a lunar mission is not so attractive: others are trying to get there as well.
US tech giant Google has offered millions of US dollars to encourage private companies worldwide to do moon missions.
At least four teams from various countries are planning to go to the moon before the end of this year, including US startup Moon Express, whose ambition is to do mining on the Moon.
China is also building a spacecraft, named Chang'e-5, to bring rock and soil from the moon back to Earth.
China's lunar rover Yutu, photoed by the lunar lander Chang'e-3 on the surface of the Moon on December 15, 2013.
China even has a plan to send a probe to Mars in 2020, while private space company SpaceX said in February that it's launching a Red Dragon 2 capsule to Mars in the same year.
Europe, Japan and India are also preparing more Mars missions.
And as for NASA's race to space? Perhaps US President Donald Trump needs to sign more bills like this one to give his scientists enough money to finish the job.
(CGTN)
