So you want to go live on Mars. It is smaller than the earth, but still has a lot of real estate. Where is the best place to call home?
NASA’s mantra was to follow the water – they’re looking for evidence of past life, but it’s always a good idea for future humans. Water is heavy and almost incompressible, so it is very difficult and expensive to take to Mars. It means to find it in situ, there on Mars, is critical to success. Water is also not just for drinking: it can be broken down into hydrogen and oxygen to create both breathable air and rocket fuel. This is the most important thing for future human presence on the planet.
And now a team of scientists has mapped out the most likely place it could be.
Mars is cold – a daily high temperature of -60 ° C is common – so any water is likely to be ice (with a few deep exceptions). Frozen water has been mapped by different missions in different ways, and most research has focused on data from a single mission or on ice in isolated locations. The team therefore put together what they call SWIM: the Mars Subsurface Water Ice Mapping project to look at the data of many missions over a wide area on the planet.
The aim was to create a system that could quantify the consistency of multiple independent observations so that they could make a strong prediction of where the water is. Note that we know that there is a lot of confinement in the refrigerators, but it is difficult to reach with spacecraft – landing requirements make it much easier to land near the equator or at the middle latitude. The ice can also not be more than a few meters deep, so it can be dug up. In other words, it must be accessible.
Given this, they looked at observations that stretched from the equator of Mars to about 60 ° north, and around the planet covering about 80% of the surface in length. The data were obtained by various methods, including neutron flux (these subatomic particles are absorbed by hydrogen in water, so their appearance can be used to map the location of ice), thermal inertia (at night rocks release heat which during the day in a way other than water ice, so that it can be used to determine where water is), geomorphology (structures and functions on the surface indicating that water is nearby, such as glaciers), and radar (reflecting water ice and rock radar pulses otherwise, which in turn allows water to be mapped).
Using a mathematical algorithm on the data, they devised a number that they would call ice consistency, where a positive value corresponds to the presence of ice, and a negative value does not correspond to it. Higher values mean stronger results.
The result: a map where accessible ice is likely to exist (and, more importantly, probably not) over a wide sample of the Martian surface.
The places with the highest values are in Arcadia Planitia, a broad, smooth plain of ancient volcanic currents, and another region called Deuteronilus Mensae, which is known to have glaciers. Both are located at the middle latitude (about 45 ° north), so it is relatively easy to access.
To evaluate their predictions, one thing the team did was look at fresh impact on the surface, where small asteroids could get through the thin air and hit the ground. If ice is located just below the surface, the collisions can dig it out, making it very clear. Over the past few years, 13 such craters have been found in cameras aboard spacecraft. The team found that 12 of them were located where their maps with great confidence predicted that ice would exist. This is reassuring.
NASA, other space agencies and even private companies want to send humans to Mars. I imagine they will read this paper with great interest.
Technology is advancing rapidly, and a human foot on Mars is not as much science as before. The first person to do so may already be walking around on earth. And now we can realistically start planning where the first charge pack can be.