Mars is dead. As the corpses move, it is very interesting: volcanoes are so large that they can change the rotation of the planet; Enough environments to support seasonal weather patterns; A cleft in its surface that makes the Grand Canyon like a roadside moat; polar ice caps; tantalizing, suggestive geological features. It is quite interesting that humanity has spent some time and effort to know this.
As of this writing there is a little plutonium-powered robot around on the floor of one of the pits of Mars, which still knows the planet. Curiosity The famous Mars is the latest in a line of expeditions, which began with the Vikings in the 1970s and continues with intermittent success to this day. Our robots, however, are just pawns. Eventually, someone will travel to an alien world, and it is inconsistent to think that their destination will be anything other than the warped corpse of Mars.
Why does the red planet hold our scientific imagination? First of all, it is a matter of convenience. It is nearby and, for some definitions of ‘easy’, is easy to obtain. Searching elsewhere will have to do things in order. But the Martian dream is not about efficiency. Percival Lowell was probably not thinking about orbital mechanics, when he drove the canals out of the planet altogether in the 19th century.
Nor was H.G. Wells when he wrote War of the Worlds. However, he was contemplating death, for the hapless inhabitants of Mars and England of the 1880s, for whom ecological collapse on a distant planet meant invasion. The relationship between Mars and war and death and blood, stretches back thousands of years. For nothing the name does not come down to us as the Roman God of War.
It is the undeniable death that now interests us. In the last few decades it is becoming clear that our favorite red planet was ever blue. There was water everywhere on ancient Mars. What we see now is the ghost of the once dynamic world.
There is a significant difference between ‘dead’ and ‘passive’. You would never say that a rock was dead (even if that rock was literally made of dead plankton!). You would never even say that Mercury was dead. Death means life. But it turns out with Mars, the language was fairly accurate. There is no evidence that biological life ever existed there, but everything else suggests that billions of years ago, the planet was a dense atmosphere, a water cycle, and everything we call a world to live in Could be required. So what happened between then and now?
Mars died, and Jupiter presumably killed it.
Mars is very beautiful as the planets move. It is about 6,200 miles, and is about 15 percent of the Earth’s mass. Now Pluto is kicked out of the club, it is the second smallest planet in the solar system, with only Mercury.
It turns out that shortening is detrimental to long-term survival at the planetary level. Separating light elements from a planet’s atmosphere requires strong magnetic fields to overcome solar radiation. On Earth, that magnetic field is driven by convection in its semi-liquid iron outer core, which creates what is known as planetary dynamo. There was also a dynamo of Mars. You will be shocked to hear that it has died.
Low-mass planets lose heat more quickly than larger ones, and while Mars still has a liquid iron core, it appears that it produces the convection needed to power a plausible magnetic field. Not hot enough for. it certainly Used To do one – you can tell by magnetized rocks when the planet was young – but no one can find any evidence of an active dynamo compared to about 3.7 billion years ago. Without a working dynamo and a protective magnetic field, much of Mars’ water was destroyed long ago by solar radiation from its atmosphere, leaving us with a very dead world.
What does Jupiter have to do with this? Good question!
The last few decades have been quite exciting for planetary scientists, who eventually have more solar systems than our own. We had our own neighborhood when we had to leave, it seemed very reasonable. Rocky planets, some asteroids, gas giants, ice giants. Nice and orderly. But when we started looking at exoplanets, it turned out that the structure of the solar system is very unusual indeed. Where are Super-Earths? Where are hot jupiters?
It is important to understand that we are now wandering far into the realm of the imaginary. Although we have some geological evidence of the dynamo of Mars, and may actually work that once water flows over the surface of the red planet, we are now trying to unravel the mysteries from the dawn of the solar system. It’s hard, and while obviously is One correct answer, it is not going to be signposted. I should also note that I am not qualified to assess these hypotheses in any way, except for ‘this interesting’ meaning.
Anyway, the most interesting hypothesis, at least where Mars is concerned, is Grand Tac. This involves the jupiter rotating like a wandering ball like the initial solar system. Jupiter was the first planet to form, and the most important. It jointly holds far more mass than every other planet, and has an incredible gravitational effect on its peers. And according to the hypothesis of Grand Tac, it once decided to fall into the sun.
The initial Jupiter did not reach its destination, but spiraled 1.5 AU or so at a distance of about 3.5 AU * from its formation point. It takes Jupiter well within the orbit of Mars, where it cannibalized almost all of the young Mars building material. You might also wonder what this little jaunt would have done to the asteroid belt. The reason it revolved around Jupiter (i.e. takedown) and retreating from the outer reaches of the solar system is Saturn, which ended in an orbital resonance that slowly retracted it to about 5 AU. And there is a good thing too, because Jupiter’s close proximity to the Earth’s orbit would mean that I certainly wouldn’t be typing that right now.
* An astronomical unit is the current average distance of the Sun from Earth.
If the hypothesis of Grand Tac is correct – there may be reasons, as you would expect from such research – the small size of Mars is easily explained: Jupiter ate it the most before Saturn was through (I As always I think of the resort involved in rescue; I don’t know why) to rescue. And so, for this complex turn of events, Mars’ dynamo faded, the atmosphere’s water was stripped by solar radiation, and the planet dried up and died.
There is another hypothesis as to what happened to the dynamo of Mars, although the most recent evidence of Martian magnetism falters over time. In theory, large enough impacts in a sufficiently short period of time may be able to stop the planet’s dynamo. Mars has seen its fair share of influences, and is in fact a period (again, at least partially hypothetical) of the history of the solar system that occurred about 4 billion years ago known as the Late Heavy Bombardment is. LHB is correct for ‘HB’, in that the inner planets are completely marked by asteroids, comets, etc., and may have large enough effectors to close the Martian dynamo. Maybe.
This, incidentally, would still be Jupiter’s defect. There are indications that the LHB may have occurred when interactions with Jupiter flowed Neptune into its current orbit, disrupting the carcasses in the Kuiper Belt and throwing a good portion of them into the inner solar system.
In other words, Mars may be a small pile of rust, but perhaps not its fault. Defect of Jupiter.