Since the late nineteenth century, Earth’s average surface temperature has risen about one degree Celsius. Moreover, new data released by the U.S. National Oceanic and Atmospheric Administration indicate that so far, this year is the second warmest year on record, despite the absence of El Niño that helped boost the global temperature to record level last year. This observation begs the question: If the current trend of greenhouse gas emissions continues unabated, what will be the global temperature several millennia from now? According to the authors of a paper published in the journal Nature Climate Change in February 2016, our planet could be a mind-boggling seven degrees Celsius warmer on average in 10,000 years. Their inference is based on the fact that a considerable fraction of carbon dioxide that will be dumped into the atmosphere in the next 100 years or so will remain potent for several thousand years, before removal by natural processes.

In a seven-degree warmer world, parts of the Earth would likely become close to uninhabitable and other parts horrifically inhospitable. The question then arises: Would humans and other forms of life be able to survive on a sizzling hot Earth? Optimists believe that just as we found a way to engineer our own doomsday, we will find a way to engineer our way out of it too.

So, what is the way out? If we are to survive, we must leave the Earth and colonise “other planets in the next century,” asserted the British physicist Stephen Hawking. Renowned astronomer Carl Sagan said: We should become a two planet species, since it is simply too dangerous to place the future of humanity on just one planet.

Out of several bodies in the Solar System, such as our moon, Jupiter’s moon Europa and Saturn’s moon Titan, the red planet Mars seems to be the prime candidate for colonisation.

What makes Mars a good candidate is its proximity from Earth, its day-night cycle which is almost the same as ours, its Earth-like seasons, enough sunshine for photosynthesis and sufficiently strong gravitational pull to retain an atmosphere. Besides, occurrence of hydrologic and volcanic processes on Mars similar to that on Earth are likely to have consolidated various elements into mineral ores that are basic and essential raw materials in our daily lives.

However, conditions on Mars are currently inhospitable for human beings. That’s because few billion years ago, the planet underwent reverse greenhouse effect. Today, the greenhouse effect on Mars is extremely inefficient. Its atmosphere, about 100 times thinner than Earth’s, is not thick enough to act as a “thermal blanket” to retain any solar energy falling on the Martian surface. As a result, average surface temperature on Mars is a frigid ‒55 degrees Celsius, with extremes that range from ‒125 degrees near the poles during winter to +20 degrees at the equator during summer. In addition, the atmospheric pressure on Mars is much less than on Earth, only 0.006 atmosphere. Furthermore, the atmosphere is too tenuous for liquid water to exist on Mars.

Thus, before we colonise Mars, we have to fix the Martian atmosphere and make it hospitable to human life. In particular, we have to crank up the planet’s thermostat to a comfortable level and make the atmosphere thicker.

Scientists across all disciplines believe that we can indeed transform Mars into an Earth-like planet by a process called terraforming. The basic idea of terraforming is simple. Introduce into the Martian atmosphere enough greenhouse gases to warm the planet to the point where the chain of events that resulted in reverse greenhouse effect is reversed. Mars will then warm up, the atmosphere will thicken and warm some more, and eventually the planet will become habitable for the Earthlings.

Several possible ways of accomplishing this task have been proposed. They range from building huge solar-powered greenhouse gas-emitting factories on Mars, to melting parts of the Martian polar ice caps using giant orbiting mirrors to reflect sunlight, to steering ammonia-rich asteroids so that they collide with Mars.

Over the last century, we have had a lot of experience in releasing hundreds of billions of tons of greenhouse gases into our own atmosphere. Thus, pumping greenhouse gases into Martian atmosphere shouldn’t be a problem for us. Researchers in the field of geophysics suggest injecting ozone-friendly synthetic greenhouse gases to initiate the warming process.

NASA is currently working on solar sail propulsion system that would use large reflective mirrors to harness solar radiation. If these large mirrors could be placed a couple of hundred thousand kilometres from Mars and aimed toward the poles, ice will melt and release the carbon dioxide and other greenhouse gases that are believed to be trapped inside the ice.

As an alternative, Elon Musk of SpaceX Company suggested dropping thermonuclear bombs incessantly on the planet’s poles to break up the ice. We won’t have to worry about radioactive fallout because Mars’s thin atmosphere would allow the radiation to escape from the planet.

Under the auspices of Asteroid Redirect Mission, NASA is developing a robotic mission to a near-Earth asteroid. The robot will collect a large boulder from the asteroid’s surface and redirect it into a stable orbit around the moon. If the mission succeeds, the technique can be used to steer asteroids into a collision course with Mars. The asteroids will ablate during atmospheric entry, thereby releasing ammonia and carbon dioxide, two cogent greenhouse gases locked inside their carbonaceous rocks.

Unlike Earth, Mars does not have a magnetic field strong enough to shield the planet from the harmful electrically charged particles produced by the solar wind. Scientists at NASA think that it is possible to deflect the solar wind by positioning powerful magnets at one of the five points, known as Lagrange Points, between Mars and Sun where the gravitational forces and the orbital motion of the magnets, Sun and Mars would interact to create a stable location.

NASA is also developing the capabilities needed to send humans to Mars sometime in the 2030s. The travel time between the two planets would vary from six to nine months – less than the longest time astronauts spent on a space station, which is longer than 14 months.

As for the time frame, once the technologies are fully developed, it would take several centuries for the greenhouse gases on Mars to rise to the levels needed for normal greenhouse effect to take over. And perhaps another one to two thousand years would be needed after that for the Martian climate to approach anything even remotely Earth-like. After all, it took the Earth billions of years to transform into a planet where life in all forms could thrive. This means we have to keep our planet habitable until we can roam freely on the Martian surface without any breathing aids.

Opponents of the terraforming program are deeply concerned about the ethics of altering another planet simply because the process represents the sorts of man-made global environmental problems that is pushing the Earth towards a catastrophic breakdown. As such, they consider terraforming to be the ultimate in “cosmic vandalism.” To advance their argument, they cite the British physician and social reformer Havelock Ellis who famously wrote, “The sun, the moon and the stars would have disappeared long ago had they happened to be within the reach of the predatory human hands.”

On the other hand, proponents of terraforming argue that sooner or later nature would take its course and eventually destroy Earth. Therefore, as inhabitants of this Universe, we have as good a claim to alien worlds as our own. Hence, it is ethically correct to make Mars suitable for human beings.

The writer is a Professor of Physics at Fordham University, New York