So first of all – apologies for the down time – or maybe you didn’t miss these posts at all. The reality is, every time I’ve sat down to write something more about this Mars thread, I’ve been sidetracked by the desire to write about some other topic of the day – like why people are surprised more than one cause gets written on a death certificate.
The reality is, more and more of those kinds of topics are going to pop up between now and the end of the year. So I’m going to bang this last Mars post out, and then return to Earth for the zaniness to come.
In the last few posts, we’ve summarized the history of our observations, reconnaissance, and initial explorations of Mars. So what have we learned about our planetary neighbor?
It’s interesting to start with the similarities to Earth. A Martian day is only around forty minutes longer than a day on Earth. Mars’ axis of rotation is also tilted at a very similar angle to that of Earth’s, so Mars experiences a similar cycle of seasons. And, while Mars is quite a bit smaller than Earth, it has a similar amount of land (on Earth, the oceans take up the majority of the surface). And, yeah, so that’s where things start to diverge…
While Earth is very near the inner edge of the Goldilocks zone, Mars is near the outer edge. The Martian year is about twice as long as a year on Earth. Gravity on Mars is about a third what it is on Earth. But these are still modest differences – now to the big stuff, which starts with something we don’t think much about in our daily lives – the Earth’s magnetic field.
Our Earth is composed of multiple layers. The outermost layer – our home — is the crust, which is relatively thin compared to the other layers, and is composed of a collection of floating plates. Under the crust lies the mantle, which is much thicker and is the source of the lava that spews out of volcanoes. The mantle is also the “ocean” of liquid rock on which the plates float, and when those plates grind against each other, we get earthquakes. Below the mantle are the outer and inner core. The outer core is also liquid, heated by the radioactive decay of its constituent elements. That heat causes convective motion in the liquid rock and metal, and that combined with Earth’s rotation lead to a dynamo effect – the outer core creates a magnetic field around our planet. Without that magnetic field, we would not be here. It shields our world from a hostile shower of energetic particles and radiation careening from our Sun, as well as from the depths of space. More directly, it shields our atmosphere, which in turn provides the retention of heat that allows for liquid water, which provided the most likely harbor for the development of life, which in turn has developed a delicate ecosystem in concert with the atmosphere itself.
In contrast with Earth, at some point, Mars lost its magnetic field. This allowed energetic particles and radiation from the Sun and the depths of space to decimate the Martian atmosphere, which in turn became thin enough that it didn’t provide enough warming of the surface to liquify whatever water might have been there. So – as far as we can tell – no magnetic field, very little atmosphere, no liquid water, no life. We do continue to explore Mars for any signs of life, whether in the present or in the past. But unless the current outlook changes, it would appear that we can ethically ask the question: what if we tried to colonize Mars and make it a second planetary home? This is the dream of Elon Musk, who seems determined and capable of at least getting us on that road. Musk’s reasoning is that we need a second home in case we or some natural disaster wrecks our primary home. But settling Mars would be a lengthy process to say the least.
For starters, we couldn’t live there today. The air is mostly carbon dioxide (you know, the stuff we exhale), the temperatures are typically far below zero, radiation rains down at lethal levels, and there is no water or vegetation to serve as the basis for human sustainment. There are two levels of dealing with that: setting up bases on Mars, and truly settling the red planet. The former would consist of some number of safe habitats (think of the movie “The Martian”), and any venturing from those would require a space suit. Even if we eventually settled on Mars, it would have to begin that way.
For human life to be even remotely close to normal on Mars, we would truly have to terraform it – make it into another Earth for all practical purposes. That would require thickening the atmosphere and infusing enough oxygen for us to breath – a thicker atmosphere would also make Mars warmer, which would melt the water from the polar ice caps – and as Carl Sagan elegantly noted in “Cosmos”, we could use canals to get the water to lower latitudes – exactly what Percival Lowell and others thought was happening over a hundred years ago. You can imagine a process of this scale would take a very long time – likely multiple human lifetimes. But I also wonder what we’d do about the lack of magnetic field – it wouldn’t do any good to build an atmosphere only to have our uncaring Sun tear it to shreds again.
I do think we need to better understand our planetary neighbor. And I also think humans will one day live there – if we survive long enough to go. And therein lies the conundrum – I think the biggest threats to our survival as a species are peaking right now, and we will have to confront and overcome them right now, or else we won’t ever colonize another world. Mars can’t be our savior, but it can be a reward for us saving ourselves.