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So you want to live on Mars. It’s smaller than Earth, but there is still a lot of real estate. Where is the best place to live?
NASA’s mantra has been to follow the water – they’re looking for evidence of past life, but for humans once and in the future, it’s still a good idea. The water is heavy and almost incompressible, so it is very difficult and expensive to take it with you to Mars. It means find it in situ, out there on Mars, is essential to success. Plus, water isn’t just drinkable: it can be broken down into hydrogen and oxygen to produce breathable air as well as rocket fuel. It is the most precious thing for a future human presence on the planet.
And now a team of scientists have mapped out the most likely spot for it.
March is cold – a high daily temperature of -60 ° C is common – so any water is likely to be ice (with a few deep exceptions). Frozen water has been mapped in different ways by different missions, and most research has focused on data from a single mission or on ice in isolated locations. So the team set up what they call SWIM: the Mars Groundwater Ice Mapping Project, to examine data from numerous missions over a large area of the planet.
The goal was to create a system capable of quantifying the consistency of multiple independent observations so that they could make a robust prediction of where that water is. Remember, we know that the polar ice caps are pretty enclosed, but these are difficult to reach by spacecraft – the landing requirements make it much easier to land near the equator or at mid-latitudes. In addition, the ice cannot be more than a few meters deep, so it is possible to dig it up. In other words, it must be accessible.
With this in mind, they looked at observations stretching from the equator of Mars up to about 60 ° north, and around the planet covering about 80% of the surface in longitude. The data was obtained by various methods including neutron flux (these subatomic particles are absorbed by hydrogen in water, so their prevalence can be used to map ice locations), thermal inertia ( at night, rocks release heat accumulated during the day in a different way from water ice, which can be used to map where water is found), geomorphology (the structures and elements at the surface indicating water is nearby, such as glaciers) and radar (water ice and rock reflect radar pulses differently, again allowing water to be mapped).
By applying a mathematical algorithm to the data, they found a number they call consistency of ice cream, where a positive value is consistent with the presence of ice and a negative value incompatible with it. Higher values mean stronger results.
The result: a map where accessible ice is likely to exist (and, more importantly, not to exist) over a large sample of the Martian surface.
The places with the highest values are in Arcadia Planitia, a wide smooth plain of ancient volcanic flows, and another region called Deuteronilus Mensae which is known to have glaciers. Both are located at mid-latitudes (around 45 ° north) and are therefore relatively easy to access.
To assess their predictions, the team notably looked at new impacts on the surface, where small asteroids may have entered rare air and crashed into the ground. If the ice is located just below the surface, these impacts can dig it up, making it pretty obvious. In recent years, cameras aboard an orbiting spacecraft have found 13 of these craters. The team found that 12 of them were located where their charts predicted the existence of ice with a high degree of confidence. It’s reassuring.
NASA, other space agencies, and even private companies are looking to send people to Mars. I imagine they will read this article with keen interest.
Technology is advancing rapidly, and a human setting foot on Mars isn’t as much science fiction as it once was. The first person to do so may already be walking around the Earth. And now we can start realistically planning where that first startup footprint is.
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