Terraforming Mars to create a world that is not like ours. (Image credit: Daein Ballard, CC BY-SA)Nearly every sci-fi story starts (and ends) with Mars being terraformed to make it more welcoming.Mars is difficult to make more Earthlike due to its cold temperatures, isolation from the sun, and general dustiness.Similar: Amazing technology: How to Terraform a Planet with'shells'A dead worldMars was once cool. By cool, I don't mean cold. Mars was a rich, carbon-rich environment, with lakes and oceans full of liquid water. It may have even had fluffy clouds. This was at a time when the sun was smaller, weaker, and sometimes much more violent than it is now. In other words, our solar systems is much more favorable for life than it was three billion years ago. Yet, Mars is still red and dead.Unfortunately, Mars was doomed right from the beginning. Mars is smaller than Earth which means that it cooled down much faster. Our strong magnetic field is powered by the spinning iron-rich goo at Earth's core. Magnetic field can stop and deflect the solar wind, a constant stream of high-energy particles exploding from the sun.Mars' core solidified when it cooled, and its magnetic field was shut off. This exposed its atmosphere to the sun's ravages. The solar wind ripped away the Martian atmosphere over the course of about 100 million years. The planet became dry when the atmosphere pressure fell to almost zero.It is so tempting: Mars was once Earth-like. Is there a way to restore it to its former glory.Polar oppositesWe humans have a lot of experience warming up the planets. Through our carbon emission over centuries, we have accidentally raised the Earth's surface temperature through simple greenhouse mechanisms. The greenhouse mechanism is a complex one. It emits a lot carbon dioxide. This is good for letting in sunlight and blocking out thermal radiation.Increased heat encourages moisture out of the oceans to become a vapor in atmosphere. This creates a blanketing layer and increases temperature. Before you know it, prime beachfront property may be better suited for an underwater submarine base.It may work on Mars if it works well on Earth. Although we can't get to the OG Martian atmosphere because it is lost to space, Mars has large deposits of water ice, frozen carbon dioxide, and more just below the surface.We could heat the caps to release enough carbon into our atmosphere to start a global warming trend. We would just need to relax, wait for physics's work to make Mars a less dangerous place.This simple idea is unlikely to work.Related: What is it like to live on Mars.Radical ideasFirst, we need to develop the technology that will heat the caps. There have been many proposals, ranging from dusting the poles with powder to make them reflect less light and heat them up to creating a huge space mirror to direct high-beam beams onto the poles. Any ideas will require technological leaps and a manufacturing presence far beyond what is currently possible (in the case for the space mirror, it would be necessary to mine approximately 200,000 tons of aluminium in space, while we are capable of mining zero tons in space).Then there's also the sad realization that Mars doesn't have enough CO2 to cause a significant warming trend. At sea level, Mars currently has less than 1% the air pressure of Earth. The Red Planet would experience 2% of Earth's air pressure if it could evaporate all the CO2 and H2O molecules on Mars. To prevent your skin's oils and sweat from boiling, you would need twice the atmosphere and 10 times as many to not require a pressure suit.We can't even talk about oxygen deficiency.There are radical ideas to counter this shortage of readily available greenhouse gases. Perhaps we could build factories to produce chlorofluorocarbons. This is a very harmful greenhouse gas. Perhaps we could use ammonia-rich comets sourced from the outer solar systems. Ammonia is an excellent greenhouse blanket and eventually separates into harmless nitrogen. This makes up most of the atmosphere.Even if we can overcome the technical challenges that these proposals pose, there is still one major obstacle: the absence of a magnetic field. Without protecting Mars, any molecule we inject (or crash into) into the atmosphere will be vulnerable to being blasted by the sun's radiation. It's going to take a lot of work to make a pyramid out of desert sand.There are many creative solutions. Perhaps we could create a huge space electromagnet to block the sun's energy. Perhaps we could wrap Mars in a superconductor to give it an artificial magnetosphere.We don't have the technology to achieve either of these solutions. Could we ever terraform Mars to make it more welcoming? It's possible that there is no fundamental law in physics standing in our way.Don't be discouraged.Paul M. Sutter, an astrophysicist from SUNY Stony Brook, is host of Ask a Spaceman, Space Radio and author of How to Die in Space.Listen to the episode "Could it really terraform Mars?" for more information. on the Ask A Spaceman podcast, available on iTunes and on the Web at http://www.askaspaceman.com. Ask your own question on Twitter using #AskASpaceman or by following Paul @PaulMattSutter and facebook.com/PaulMattSutter.