There are too many potential natural/man made catastrophes that put the existence of the human specie at risk of extinction. In fact, our fate on earth is inevitable. For this reason, it's imperative that humans spread out and seek refuge amongst the stars.
Where should such a pursuit begin? And what potential habitable candidates are currently at our disposal?
First of all, any planets that are not within our solar system can immediately be ruled out as we don't currently possess the know-how for interstellar travel. Oh ya, and of course the Wait Calculation makes the prospect of a such an endeavor simply irrational.
Now, we got that out of the way let's start with the following question: What conditions do humans require to harbor life?
Our candidates which are worthy of discussion are Saturn's Moon - Enceladus, Jupiters Moon - Europa, Earth's Moon, Venus and Mars.
Saturn's Moon - Enceladus and Jupiters Moon - Europa: We can discuss a whole array of pros and cons, but discussing a single point should suffice in making an argument. Fortunately, these two moons have active chemistry and liquid water (YES! LIQUID SALT WATER, although the sun is very far, friction generated by the neighboring moons and the host planet itself provides heat to the moon's core). Unfortunately, with current tools at our disposal, a trip to either moon entails too much exposure to cosmic radiation and the risk of the passengers dying before arriving to their destination is very high (as determined by NASA). Long term hibernation is still that of science fiction. However, these are likely the MOST promising terrestrial bodies to harbor life and what their moons have in store for us is likely nothing short of fascinating.
Earth's Moon: So, why are we all tripped up about going to Mars when the moon is nice, lonely and only 238,900 miles away from earth (relative speaking, that's super close). Plus, we've already successfully traveled to this destination.
In fact, there are a few to-be endeavors for colonizing the moon and such a pursuit can be economically viable as scientist speculate that hydrogen can be beneath the moon's dusty surface, which can be used as an efficient source of fuel. It's rumored that Russia has plans to colonize our moon by 2030. Furthermore, the CNSA (China National Space Administration) has sent a rover to the moon in 2013. In 2014, China’s state newspaper reported that a lunar colony is in the works, citing Zhang Yuhua, deputy chief designer of the Chang’e 3 lunar mission. “In addition to manned lunar landing technology, we are also working on the construction of a lunar base, which will be used for new energy development and living space expansion,” Zhang said.
All sounds good so far? Although it's not a bad idea, here comes the bummers. The moon has zero atmosphere which exposes any potential life form on the its surface to deadly cosmic radiation, solar radiation and meteorites. Furthermore, the moons gravity is far weaker than Earths. Although reduced gravity sounds great, it leads to all sort of bone and muscle diseases. Astronauts in low earth orbit were reported to have lost bone mass at about 10X the speed of persons with osteoporosis. Objectively, forcing the smallest change in human physiology is best (not to let Natural Selection get the best of us) and therefore maintaining an environment as similar to earth as possible is ideal for our survival. Also, studies have been done which showed that a low gravity environment can cause sperm to act in a very strange way, making procreation a huge issue (click here for more). Lastly, the moon is littered with Regolith, microscopic shards of jagged glass which are very hard to isolate, are destructive to equipment, and are detrimental to human respiration.
I believe, with engineering and technological advancements, colonizing the moon is entirely possible, in fact, it's probable that such will occur in our lifetime. What people tend to forget is the political ramifications when trying to return to the moon. NASA is funded by the US Congress and getting approval for space exploration is grim, let alone appeals are likely reconsidered every 4 years. The US Congress is cutting funding left and right for most cosmic proposals and the prospect of getting funding to return to the moon is currently out of the question. NASA would likely use the limited budget to explore terrestrial bodies in which we currently know little about.
Venus and Mars: Mars has been a fixture of our collective continuousness for centuries. How does it stack up when compared to Venus.
- Venus is 30%-50% closer to earth when compared to Mars. That's a huge deal, less costly, less exposure to radiation and transporting survival materials to Venus is much more affordable.
- Venus is much closer to the sun. Solar energy is a great source of renewable energy.
- Venus has .9 earth's gravity as opposed to mars which has .4 earth's gravity (and of course, the point was discussed earlier in this blog)
- Venus has a lot more available CO2 in which you can serve as a useful oxygen source.
- Venus has a thick atmosphere, in comparison to the almost non-existent atmosphere on Mars, which means: better protection from solar radiation, cosmic radiation and meteorites.
So, why does Mars get all the hype? the differences can be seen in the cons of Venus. Venus' surface is entirely uninhabitable. There is so much CO2 trapped in Venus' atmosphere that its surface temperature is > 450 degrees C (that's like, really hot!), not to mention the barometric pressure which is OVER 90 earth atmospheres (enough to crush a US military grade submarine). However, and interestingly enough, hovering just above Venus' surface CAN harbor life (no, i'm serious!). NASA has already started a project called HAVOC (click here for more information)
Summary: Interstellar space travel is ruled out because the Wait Calculation and limited technological capabilities. Saturn's and Jupiter's moons sound ideal but we still have engineering challenges to overcome with respect to distant space travel. Earth's moon has an abundance of detrimental dust particles, gravity can be dangerous for human survival and congress is likely not going to fund any moon like operation for the foreseeable future. Mars, although a little far and posses many challenges, definitely seems like the most viable option :)