Dreams of transforming Mars into a habitable long-term human colony are scientifically impossible with current technology, according to a NASA-sponsored study.

Transforming planets as a pre-cursor to colonisation is a staple of science fiction, and an aspiration for individuals including Elon Musk, whose company SpaceX uses images of terraforming Mars in its promotional material.

In the 1898 science fiction novel War of the Worlds, the invading Martian forces bring a red weed with them that begins to kill off Earth's plant life to make the planet habitable for the Martians.

This process of colonising other planets is known as terraforming when it refers to shaping their environments so they are more like Earth.

However, for planets which do not harbour any life - and certainly not complex life - it requires far more than introducing species which human society lives beside.


Thickening Mars' atmosphere would be essential to keep liquid water on its surface, which would be essential for long-term colonisation.

Greenhouse gases such as carbon dioxide (CO2) would be vital to do this, but they are not present on Mars in high enough quantities to provide any significant greenhouse warming, said Dr Bruce Jakovsky.

"Our results suggest that there is not enough CO2 remaining on Mars to provide significant greenhouse warming were the gas to be put into the atmosphere," said Dr Jakobsky from the University of Colorado and the lead author of the study, which was published in Nature Astronomy.

Image: Mars would need a much thicker atmosphere to sustain liquid water

"In addition, most of the CO2 gas is not accessible and could not be readily mobilised.

"As a result, terraforming Mars is not possible using present-day technology."

Even though some water may have been discovered there, Mars has less than 1% of the atmospheric pressure of that on Earth.

The study finds that even using all of the sources of carbon dioxide and water on Mars to thicken the atmosphere would only increase pressure to 7% of that on Earth, "far short of what is needed".

Although potentially greater reserves of CO2 could lie deep beneath the Martian surface, these are not easily accessible.

The scientists say that any successful effort to terraform Mars could only be completed in the very distant future.