Terraforming or creating a habitable environment on Mars, that would allow humans to explore it without life support, is still a far-fetched dream, say scientists who found that existing technologies are incapable of forming an Earth-like atmosphere on the red planet. Science fiction writers have long featured terraforming, the process of creating an Earth-like or habitable environment on another planet, in their stories. Scientists themselves have proposed terraforming to enable the long-term colonisation of Mars.
A solution common to both groups is to release carbon dioxide gas trapped in the Martian surface to thicken the atmosphere and act as a blanket to warm the planet. However, according to scientists from University of Colorado, Boulder in the US, Mars does not retain enough carbon dioxide that could practically be put back into the atmosphere to warm the planet. Transforming the inhospitable Martian environment into a place astronauts could explore without life support is not possible without technology well beyond today's capabilities, researchers said.
Although the current Martian atmosphere itself consists mostly of carbon dioxide, it is far too thin and cold to support liquid water, an essential ingredient for life. On Mars, the pressure of the atmosphere is less than one percent of the pressure of Earth's atmosphere. Any liquid water on the surface would very quickly evaporate or freeze. Proponents of terraforming Mars propose releasing gases from a variety of sources on the Red Planet to thicken the atmosphere and increase the temperature to the point where liquid water is stable on the surface.
These gases are called "greenhouse gases" for their ability to trap heat and warm the climate. "Carbon dioxide (CO2) and water vapour (H2O) are the only greenhouse gases that are likely to be present on Mars in sufficient abundance to provide any significant greenhouse warming," said Bruce Jakosky of the University of Colorado, Boulder. Although studies investigating the possibility of terraforming Mars have been made before, the new result takes advantage of about 20 years of additional spacecraft observations of Mars.
"These data have provided substantial new information on the history of easily vaporised (volatile) materials like CO2 and H2O on the planet, the abundance of volatiles locked up on and below the surface, and the loss of gas from the atmosphere to space," said Christopher Edwards of Northern Arizona University in the US.
The researchers analysed the abundance of carbon-bearing minerals and the occurrence of CO2 in polar ice using data from NASA's Mars Reconnaissance Orbiter and Mars Odyssey spacecraft, and used data on the loss of the Martian atmosphere to space by NASA's MAVEN (Mars Atmosphere and Volatile Evolution) spacecraft. "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 Jakosky.
Although Mars has significant quantities of water ice that could be used to create water vapour, previous analyses show that water cannot provide significant warming by itself. Temperatures do not allow enough water to persist as vapour without first having significant warming by CO2, researchers said. Taken together, the results indicate that terraforming Mars cannot be done with currently available technology. Any such efforts have to be very far into the future, researchers said.
