## Posts Tagged ‘Drake Equation’

### Life Could Have Evolved On Mars, That Was A Major Advance In Understanding.

March 16, 2021

The most important point with Mars is the following, and it is already established, except for what would be one gigantic scientific surprise pertaining probably to biology. Life Could Have Evolved On Mars.

Imagine just this: that Mars would have been twice larger in radius. The martian radius would then be 6,800 kilometers, ten percent bigger than Earth. Assume next that Mars had been of the same density as now. Thus its mass would be 2^3 = 8 times its present mass. Now the gravity on the surface would be different. From the [mass/(distance)^2] law of gravity (which is older than Newton, and true to this day), one sees Martian gravity would become 8/(2^2) greater. In other words, two-thirds of Earth’s gravity.

So a bigger Mars would have found it easier to keep its atmosphere… and in particular the most potent greenhouse gas, water vapor.

Martian rocks look normal, like Earth surface rocks: there are carbonates, sediments, and normal-looking lava. Yet… Think about that. Martian density is a tad below 4 grams/((cm)^3): 3.93 g/cm³. Earth density is 5.51 g/cm³

What’s the origin of the difference? The core of the Earth has lots of iron… but not just that. Earth is actually the densest planet: it is denser than Mercury (5.43) and Venus (5.24). The gas giants are of course much less dense, denser than water by a third (Jupiter) or two-third (Neptune)… Saturn, if one could put it in a tub on Earth, would float, with only ⅔ immersed…

I have long viewed the core of the Earth as a giant nuclear reactor, and my good friend the geophysicist Mark Jellinek, a Miller Fellow, became very angry about this, and we stopped seeing each other because of this scientific debate, where he defended the status quo, which was then that the Earth was releasing heat mostly from contraction (as Jupiter does, supposedly) and latency. Since then the consensus has gone my way. My approach was that of a physicist

This Earth Nuclear Reactor is life giving, because it enables Earth to generate a powerful magnetic shield which wards off the 400 kilometers per second solar wind, and probably reduces the atmosphere robbing potential of Coronal Mass Ejections (CME).

Venus has no self-generated magnetosphere… differently from Mercury, Jupiter, or Saturn; Mars is too small to have a churning metallic core, so has no magnetosphere, thus CMEs tear the Martian atmosphere away, in particular water. Instead Venus has an induced magnetosphere. A pathetic device that could not prevent Venus from being deprived of all its hydrogen, hence water, torn by the solar wind, especially during Coronal Mass Ejections CME.

Having not much magnetosphere on Mars is a bit less of a problem: Venus is 100 million kilometers from the Sun, Mars, 240 millions kms. So solar radiation on Mars, per surface area, is one sixth of that of Venus… Venus is a torrid hell, from too much greenhouse, while Mars is too cold, from not enough greenhouse.

Superficially, Venus and Earth are sister planets, both rocky, with roughly the same mass. However there is a huge difference, deep inside: Earth has a giant metallic churning core, and Venus doesn’t. This means that habitable planets to generate life need more than the right mass: they need the right core. I have made that argument many times

Now back to our twice-bigger, eight times more voluminous Mars. Suppose now we endow it with a big radioactive, high density core: we could get to the same mass and gravity as Earth. Then there would be a magnetic field (there is plenty of Iron, Fe56, on Mars, that’s why it’s red!), the CMEs would have been less of a problem, the CO2 and H2O would have been retained…. However with plenty of H2O, Mars would have frozen over, sent back the radiation to space, and it would be a shiny crystal snowball…

Not easy to win at terraforming… NASA agrees that terraforming Mars by using Mars itself is impossible with present technology … However, what NASA did not consider is that a foreseeable technology would be just to harness the solar wind, or get water from Jupiter (not its satellites which have plenty… and we need it there)

The main point of this essay is this: at first sight a larger Mars could have sustained life… Supposing that some of the mass which went to Venus had gone to Mars… However, a more refined analysis shows that Earth also found, and stole the radioactive core necessary to generate a magnetic field making the sustainable evolution of life possible. Ergo, the Solar System had just enough for one Earth where it happens to be …

Some have argued that discovering life on Mars would be a gloomy event: it would show that life is common in the universe…. as I think and this essays shows. What the pessimists say is that then, if life is common, there have been plenty of technological civilizations in the galaxy, but no galactic empire, so all these civilizations were crushed by a mysterious event, a systemic occurrence. But the gloomists’ logic is too rapid. Life on Mars now gone or near extinctions proves instead my point: there may be hundreds of billions of habitable worlds in the galaxy… So what? The evolution of life on Earth took more than four billion years. On Mars, the evolution of life may have been sustained for a billion years, and then the planet got dessicated, hostile to life… A typical case in my view [1]… Forty billion Earths does not mean that more than one could develop animals, let alone a civilization beyond stones and sticks.

Ah, last but not least. A big discovery overall, is that from the poles of Mercury to the ice mountains of Pluto, the Solar System turns out to be surprisingly inhabitable… because it’s full of water in many unexpected places. It is imaginable life could have developed on Europa, even Enceladus… And certainly Mars. It’s all there for the taking… Although microbial Martians would be a serious problem… there is little doubt that, armed with fusion, we can settle, say, Ceres…. All we really need is to fabricate compact thermonuclear reactors, to generate all the energy colonization and terraforming will need (although on Mercury, solar panels will do just fine).

Scientific understanding proceeds in subtle ways. The more we understand about Mars, the more we understand about life, and that is just the beginning. Life probably started there, and then degenerated, as life sustaining water was torn away. The Martians existed for a while, but they were biologically retarded… How similar was that life? Did we, Earth life, originate there? What consequences for life throughout the galaxy? And for civilization, looking backwards and forward?… Not even Pluto is the limit…

Mars will double the real estate readily accessible to humans…

Patrice Ayme

***

[1] The fate of Mars can enlighten the Drake equation. At first sight we have a planet, Mars, where life died after a billion years. Also life may have got started on Venus, and died there for a similar reason (no magnetic shield). We don’t know how many times a planet is both in the radioactive belt and the habitable belt. Being really gross about it, we can say that, even in an hospitable star system as Sol’s there was (1/3)^4 ~ 1/100 that life lasted long enough to evolve animals…

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