Imagine this scenario set in the future. We know that a decently large rogue planet will be crashing into Earth in a certain number of years and we cannot do anything to stop this from happening. However, we do have the ability to terraform a planet. If we could also move humanity to either Mars or Venus, which one should we go for and why?
Hi Jessica!
Interesting question. To start off, I will define what terraforming is for those who do not know what it means. Terraforming refers to the hypothetical process of modifying a planet or other heavenly body in order to make it habitable by humans. This outcome can be achieved by changing the atmosphere’s competition, the body’s temperature, the surface topography or the planet’s ecology. In order for terraforming to be successful and the planet to be able to sustain life, NASA has defined that such a body must have extended regions of liquid water, favourable living conditions and enough energy sources to sustain metabolism ().
Mars is generally understood to be the planet that is closest to fulfilling these criteria because in many respects it is the most Earth-like planet in the Solar System(). It is generally accepted by scientists that Mars once had an Earth-like characteristic including a thicker atmosphere and abundant sources of water. These characteristics have diminished over the course of hundreds of millions of years due to carbon dioxide/carbonates reactions, a lack of magnetosphere and numerous asteroid impacts. The biggest challenges to colonising Mars are low gravity, which prevents Mars from retaining an artificial atmosphere, and the health threat from cosmic rays. Despite this, Mars is ideal for terraforming because it exists on the outer edge of the habitable zone where greenhouse gases could support the liquid water on the surface at a sufficient atmospheric pressure; thus, Mars has the potential to support both a hydrosphere and a biosphere. Further, the soil and atmosphere of Mars contains many of the main elements needed for life (). Large amounts of water ice exist below the Martian surface, which can be heated up to provide abundant sources of liquid water. Large amounts of oxygen can also be found in metal oxides and in the soil as per-nitrates, although molecular oxygen only exists in minute amounts. This is advantageous because electrolysis could be used to separate the abundant water on the planet into oxygen and hydrogen if sufficient electricity were available.
Terraforming Mars would entail three major and related changes: increasing the atmosphere, increasing the temperature and preventing the atmosphere from being lost due to low gravity. Increasing the atmosphere is important as the current atmosphere is relatively thin and has a very low surface pressure. As the atmosphere builds up, the greenhouse effect would start to occur, which will help heat the planet and melt the frozen ice. The process of melting the frozen ice will create water vapour, which will augment the process. Ammonia could be imported from Earth as a powerful greenhouse gas; this would have the effect of improving the greenhouse effect and contributing to the mass of the atmosphere. Another method of increasing temperature would be to direct small asteroids from the larger impeding asteroid onto the Martian surface through the use of high power lasers, which would release heat energy onto the planet through the impact and therefore sublimate CO2 or vaporize water into greenhouse gases. Impacting asteroids onto the planet’s numerous nitrate beds would also release additional nitrogen and oxygen into the atmosphere.
Terraforming Mars has been arguably easier than terraforming Venus due to the requirements that terraforming Venus requires. First, Venus has an extremely dense 9MPa carbon dioxide atmosphere; this atmosphere would need to lightened in order for living to occur. Secondly, the planet’s temperature is simply too high for living; at 450 degrees, human life would be unable to cope. The changing of these two aspects of Venus would require an energy and resource consumption in order to decrease the temperature and making the atmosphere breathable that far outstrips that of terraforming Mars. Finally, the colonisation of Venus is impossible at today’s technology. In contrast, it is generally accepted that governments and technology of today are advanced enough to proceed with terraforming Mars, however the allocation of such massive resources needed in colonise Mars has rendered the project unfeasible.
However, the analysis above assumes that technology at this point in the future would be the same as technology today. Given that there are no impending planetary collisions for at least a thousand years ahead, and the fact that technology is now growing at the fastest pace it has in history, then technology tens of thousands of years later will definitely be completely different to that today. It may be possible that technology will be developed that runs on heat energy – in that case, it may be easier to terraform Venus. It may even be possible that technology at that point in time would be so far advanced that terraforming both planets would be a piece of cake, or possible that the two planets would have already been colonised. In fact, I would be inclined to believe that technology at that point in time would be enough to destroy any incoming planet or even to build new planets out of nothing. It is always important to take into account context; thus, I don’t think there would be much trouble in the future if an asteroid decides to crash into us!
Indeed, this raises up an interesting point. Let’s say that in a million years, your supposed planet is about to collide with Earth. What do you think the state of technology will be in a million years? Do you think we would have already depleted Earth of its resources and started living on numerous other planets? I really think it would be cool if we could catch some sort of space train from Mercury to Neptune, similar to how we catch the train today to get from Strathfield to Central. Oh, what I would give to be alive In a million years!