Where did it all go wrong: a tale of life on Mars

By Miles Gilroy, SciTech Deputy Editor

In Epigram's 2024 Freshers print, I wrote an article about photolysis, a process that we believe happened in the atmosphere of Mars billions of years ago and could be the initial process required for life to emerge. In that article, I mentioned that, due to the similarity between early Mars and Earth, it is likely that, if photolysis happened on Mars, it also happened on Earth and could be the reason we have life here. But this leads to the question of why there is such diverse and complex life on Earth while Mars is a barren, seemingly lifeless wasteland - at what point did Earth and Mars become so different and why?

We aren’t entirely sure why this ecological disparity exists. However, it is very likely that the answer lies in the fate of the liquid water (as mentioned in the photolysis article), which is vastly different for the two planets.

Thanks to our extensive surveys of the surface of Mars, we know that it was once like Earth still is: teeming with flowing rivers and dominated by magnificent oceans and lakes (this is evident from the meticulous carving of the surface that could only be a result of water flow). However, with just a brief look at the red planet today, it is obvious that this is no longer the case - it is dry… drier than a nun’s [joke redacted].

So what happened to all of Mars’ water? Two words: magnetic field, well, global magnetic field, so technically three words. This may sound irrelevant, but all will become clear. Mars has localised, remanent magnetic fields, meaning some parts of the surface (ferromagnetic parts) still produce magnetic fields. But it doesn’t have a global magnetic field like Earth does. Basically, Earth is a giant magnet and Mars is not, although it is covered in small ones. These remanent magnetic fields point to the existence of a global magnetic field in the past, but this has since been lost. 

Global magnetic fields are generated by the rotation of liquid iron around the core of a planet. It is unknown why Mars lost its magnetic field, but it is likely due to partial solidification of its core, reducing the rate of rotation. Anyway, without a magnetic field, Mars is vulnerable to solar winds,  streams of charged particles originating in the sun. When these particles approach Earth, they are deflected by the magnetic field, but when they approach Mars, they just pass straight through the atmosphere, pushing molecules out into space. 

We believe that this is what happened to most of the water on Mars. It evaporated and rose into the atmosphere only to be broken down by solar UV radiation into hydrogen and oxygen (photolysis), at which point, the lighter hydrogen was swept away by the solar winds, and the heavier oxygen oxidised the surface, creating a rusty-looking, red planet.

After a few billion years, all the liquid water was gone, lost to space. But it’s not all bad news for Amy Wong or the Ice Warriors. Recent analysis of data from NASA’s InSight mission suggests that there is still enough liquid water on Mars to cover the entire surface in a one to two kilometre deep ocean. 

The InSight lander, equipped with a seismometer, was sent to Mars to study the composition of the planet. It measured seismic waves and determined what materials they had travelled through based on their speeds, since the speed of a seismic wave depends on the density of the medium. Using this method, the same that is used on Earth to find oil reserves, Vashan Wright and Matthias Morzfield of the Scripps Institution of Oceanography at the University of California, San Diego and Michael Manga of the University of California, Berkeley deduced that many of the waves had passed through rocks that were saturated with liquid water between 11.5 and 20 kilometres below the surface.

Unfortunately, due to the depth of these reservoirs, it is extremely impractical to study them properly. For reference, the deepest hole ever dug on Earth is the Kola Superdeep Borehole in Russia at 12.2 kilometres deep. This was a result of 20 years of digging that eventually had to be aborted because the temperature became too high for the equipment to function. So, mining a hole deep enough to find this water would be hard enough on Earth, let alone 140 million miles away on a practically atmosphere-less planet. But, just because we can’t reach it, it doesn’t mean life can’t exist down there. In fact Manga says ‘I don't see why [the underground reservoir] is not a habitable environment.’ There are similar places on Earth that happily support life.

Life on Mars remains a mystery, but it also remains a possibility

We believe that photolysis happened in the atmospheres of Earth and Mars billions of years ago but, due to some magnetic field issues, Mars’ atmosphere was mostly swept away by solar winds, while Earth's grew into a complex array of organic chemicals, synergistically supported by life. This realistically leaves the water that escaped into the crust of Mars as our last hope at finding cosmic neighbours. Life on Mars remains a mystery, but it also remains a possibility.

Featured image: ESO/M. Kornmesser

Do you think life could be hiding in these underground reservoirs?