Colonizing the Moon has been claimed to be the stepping stone for colonizing planet Mars (NASA: “En Route to Mars”). Some folks are all in favor, with headlines like “Make American First on the Moon again!”
Even the renowned astrophysicist Stephen Hawking has been adamant in his doom scenario projections: In one hundred years or so, mankind can no longer live on earth. That’s a big “upgrade” from “… one thousand years …” that Hawking made just a few months ago. No wonder then, the (renewed) race to the moon and planets (not limited to Mars) is just getting underway.
The idea of the Moon as a gateway to colonize Mars and other planets now leads to questions of suitable housing for those (presumably happy) future colonists on any of these heavenly bodies. In turn, that new requirement fosters research into materials that could be useful for the purpose, including concrete. Recent research activities under way explore the formation and structural strengths of concrete under reduced or near-absent gravity, like in parabolic flights with suitable airplanes.
Parabolic FlightsParabolic flights start from mid altitudes of around 8 km height. The airplane then goes into a steep ascent that is followed by a steep descent. Between the inflection points of the ascent and descent a brief (10-20 second) period of a near weightless environment exists in the plane that allows undertaking some testing experiments. The French company Novespace has modified an Airbus airplane, model A310-304 VIP, to allow such flights; the plane has been dubbed A310 ZERO-G.
If the chemical reactions are rapid enough, microscopic crystal growth and bulk strength of the resulting material can be studied. The formation of concrete and specific concrete mineral components like ettringite is just one of many items of interest.
What is Concrete?
Regular cement, also widely known as Portland Cement (i.e., the dry material) that you can buy in 60 lb bags at many outlets, is the most common type of concrete-forming material. It is basically a mixture of calcium and aluminum oxide and silicate with small amounts of magnesium, iron, and sulfate minerals. This powdery mixture, upon reaction with water, forms a variety of hydrated minerals that crystallize into a densely-packed arrangement of such micro-crystals. The resulting concrete is like a hard rock that withstands the ravages of time much better than most other building materials.
In fact, there are few large land-based structures that do not contain concrete in one form or another. Accordingly, the world’s annual production of cement is in the order of billions of tons and one major energy use. What some people seem to forget though is that the formation of concrete does not just involve a dry powder but also another vital ingredient, generally known as WATER. For quality concrete to form, the water to cement ratio needs to be approximately 0.3. Without any water for the powder to react with to form concrete, nothing happens.
So when some potential future colonists or material engineers dream of building concrete skyscrapers or the like, anywhere in the universe, that little requirement of water is often overlooked. Even if cement could easily be produced from heating some rocks there, dear colonists-in-waiting, there simply is no water to tap, neither on the Moon nor on Mars.
Water, Water everywhere
NO, not at all!
If you want to find copious amounts of water, then better stay close by. Due to the coincidence of the seasonal spring runoff and heavy rainfall in recent weeks, some folks along the shores of rivers and lakes in Quebec are currently wishing for less water. Their basements are flooded and the Province has called for help by the army to provide relief from the rising “tide.”The “Blue Planet,” planet Earth, is especially endowed with copious quantities of water—in contrast to the Moon or planet Mars. Perhaps, those bodies may have had plenty of water too, eons ago, but they do not now. For example, the so-called “polar ice caps” on Mars consist of “dry ice,” which is a term used for solid carbon dioxide—not frozen water. Unfortunately for all would-be-colonists, the Moon has neither an atmosphere nor any known deposits of water either—and water is vital.
Water is Vital
Have you ever wondered how the astronauts on the International Space Station (ISS) are keeping hydrated? Then perhaps, you know that they are living by drinking their own (purified) bodily fluids. That’s a fact; not to mention the high-energy radiation exposure from space. No wonder, even the ISS is under threat.
So, dear hopeful astronauts, eager Moonlings and Marslings, sorry to have to crimp your expectations, no comfy high-rise condos on either the Moon or Mars anytime soon, not even concrete bunkers—regardless of Hawking’s proclamations with which not everyone agrees. For example, as A. Ozimek writes in Forbes magazine, “Sorry Nerds, but colonizing other planets is not a good plan.”
But never mind, just keep on dreaming!