While we still have plenty of more years of Earth left, scientists are continuing to explore ways to colonize Mars, and not just in case we need to flee our planet, but for Space exploration purposes. The main thing that is preventing us from making more headway (apart from the distance between the two planets) is the fact that Mars has a very thin atmosphere, and scientists believes that is due to a lack of magnetic field in the red planet.
The current theory is that Mars probably did have a magnetic field a long time ago, as data from NASA’s InSight lander has suggested, but the weird thing is that this magnetic field seems to have only covered the southern half of the planet. Since the field acts as a protective bubble, solar wind just chipped away at the planet’s gases over billions of years creating the lack of atmosphere we know today.
The new findings about Mars’s atmosphere
This surprising data from the InSight lander prompted researchers at the University of Texas Institute for Geophysics to begin looking for answers, and one of the theories they managed to come up with posited that Mars’ core might have been totally molten back then, causing the lopsided magnetic field.
Those who know a bit of Earth geology might be confused by this theory, as Earth’s core is usually represented by a ball of molten lava, but it is actually split into two parts. There is a solid inner core surrounded by a liquid outer one and it is the outer core that is responsible for generating Earth’s magnetic field, thanks to the movement of molten iron and nickel.
Given this fact, scientists have extrapolated that Mars had a similar setup billions of years ago when its magnetic field was active, but sometime after 3.9 billion years ago, that field vanished. We know this as man rocks from massive impact basins like Hellas and Isidis, which have been dated as formed during that period, would have kept traces of magnetism if a field was still active and they do not, suggesting that the magnetic field was already gone by then.
The reason for the cooling of Mars’s core is what is still a mystery (in the hypothetical case that these theories are true), but it would explain a lot about the planet’s atmosphere. If it turned solid, it would have shut down the internal motion that creates a magnetic field solving the mystery of the current state of the atmosphere, but what about the previous mystery? Why was the magnetic field so uneven before it disappeared?
The southern hemisphere showed strong magnetic traces, while the northern half was basically blank, which was first noticed during the Mars Global Surveyor mission back in 1997, and InSight confirmed it years later. Over time, scientists have tossed around a few ideas about what could have caused that like giant asteroid crashes. Others blamed early tectonic shifts. But none of those explanations held up over time.
Here is where the University of Texas team, led by Chi Yan, comes in with a new theory. Their idea has two parts: Mars had a fully molten core, and there was a huge temperature difference between the northern and southern hemispheres. This temperature difference is what would have caused heat to escape mostly from the south, which would have powered the magnetic activity only in that region.
To back this up, the team built a computer simulation of early Mars using a supercomputer at the Maryland Advanced Research Computing Center. They tweaked things like how the molten core flowed and how well the crust in each hemisphere conducted heat and found that the setup that best matched real Mars data was one where the whole core was liquid, and heat flowed way more easily through the southern hemisphere than the northern one.