[Original research, as usual, explaining in a bit more detail the preceding essay, its allusions, and its background: I pointed out that Venus failed as a livable planet because of its different internal composition. I turn then that argument around to demonstrate habitable large “Super Earths” are perfectly plausible, because “Super-Earth” does not have to mean “Super-Gravity”. I ponder the reasons pushing some astrophysicists to be so dead set against Super-Earths, and track that to the usual submission to the present plutocratic Zeitgeist.]
Usually, among astronomers, the term “Super-Earth” denotes a ROCKY planet with a mass higher than Earth’s. This does not imply anything about the surface conditions, habitability, or the potential presence of indigenous life.
In the Solar System’s icy gas giants Uranus and Neptune are 15 and 17 Earth masses respectively. My idea behind the concept of Super-Earths is to avoid “Gas Dwarfs”, also called “Mini-Neptunes”, by keeping the mass low enough.
What matters, to determine the livability of a rocky planet, is its surface gravity, and its composition regarding water and magnetism. It’s not as simple as Huyghens had it: “How vast those Orbs must be, and how inconsiderable this Earth, the Theatre upon which all our mighty Designs, all our Navigations, and all our Wars are transacted, is when compared to them.” -Christiaan Huygens (17th Century; Huyghens was financed by the tyrannical Super Plutocrat Louis XIV, an intriguing twist).
3,500 planets have been found around other stars (March 2017; the High Provence observatory found the first, and then the French satellite Corot found plenty, followed by NASA’s Kepler). A great percentage of them are Super Earths in the usual sense of being more massive than Earth, but less than Uranus.
In my terminology, a large Super Earth is not necessarily a gas giant. It may well be livable. (The reason to insist on all this is that I want money for super-telescopes, which are technically feasible, now; it’s just a question of money! If one listens to Siegel/Forbes below, one would decided to only finance financiers, since they pay more…)
Ethan Siegel, a celebrity astrophysicist who writes for Forbes magazine, disagrees with the whole mood behind the concept of “Super Earth”.
Siegel claims that Super Earths are never habitable, let alone earthly: “There’s no such thing as a ‘habitable Super-Earth’. Earth is pretty much the limit of how large you can get and still be rocky. Anything much larger, and you’re a gas giant.”
Bemoans Siegel: “For a long time, we thought our Solar System was the template for the planets we’d find in the Universe. Inner, rocky worlds dominate the hottest part of the Solar System, with large, gaseous planets orbiting much farther out. The largest rocky planet was Earth; the smallest gas giant was Uranus; the mass difference between the two was a factor of 17, with Uranus having four times Earth’s radius. So it was quite a surprise when exoplanet discoveries started rolling in. Not only can planets of various sizes and masses appear anywhere in a solar system’s orbit, but of all the mass-and-size combinations out there, the most common type of planet is one we don’t have at all: a Super-Earth.
May these worlds be home to the realizations of our extraterrestrial dreams? Ethan Siegel arrogantly nix the idea: “… a cold, hard look at the scientific facts — and at the physics behind planetary science — puts the kibosh on that in no uncertain terms. In fact, the most up-to-date science tells us that the very idea that there is such a thing as a “Super-Earth” is a failing on our part.
Ethan Siegel again:
“The planets that we’re searching for, ostensibly, are the ones that are the most Earth-like: with similar compositions, atmospheres, masses, temperatures and other conditions to our world. But until we actually find life on another world — or learn a whole lot more about these planets we’re only beginning to discover — we can’t be sure which conditions are mandatory for intelligent life and which ones are mere happenstance. When we classify worlds as Earth-like, we look to their radius and how much energy they receive from their star.
In the past, we’ve typically said that if these worlds are approximately the size of Earth and receiving approximately as much energy-per-square-meter as Earth, these are likely Earth-like worlds. But this was an assumption that we made prior to having enough data to draw a conclusion… thanks to follow-up observations of their pull on their parent star, we’ve obtained the mass for hundreds of these worlds. And the conclusion they point to is damning.”
The basic argument Ethan (and others from MIT, etc.) hint to is that Super Earths have such a high surface gravity, they hang onto considerable amounts of hydrogen and helium. Then the atmosphere becomes crushing, life can’t develop.
Professor Ethan claims, without iron-clad evidence that:
“… the transition from “rocky” world to “gaseous” world occurs at just twice the Earth’s mass. If you’re more that twice the mass of Earth and you receive the same amount of energy from your star, you’ll be able to hold onto a substantial hydrogen-and-helium envelope of gas, creating an atmospheric pressure that’s hundreds or even thousands of times as great as what we have on Earth’s surface. The hope that Super-Earth worlds would be Earth-like is shattered, and we can safely put Super-Earths, Mini-Neptunes and Neptune-like worlds into the same overall category… it’s important to remember that even calling a world a “Super-Earth” is evidence of our bias. “
All too many scientists tend to be biased about bias. Why the hysteria?
But I repeat myself: Ethan Siegel works for Forbes.
His preceding conclusion is, In My Not So Humble Opinion (IMNSHO), flawed: it depends upon surface gravity, hence hypotheses about a planet’s internal composition. Basically, those scientists scale up the composition of Earth to Super-Earth”. But we have no proof of that. Quite the opposite, we have indication to the contrary.
I already talked about Venus. Venus is nearly Earth-size is Venus’ magnetic field is weak, and make the planet appear like a comet (observing with some instrumentation).
Venus shows us a probably different composition: it is less massive because it does have Earth’s heavy radioactive iron core:
Primitive Mathematics & Geology Show Surface Gravity Can Be Low On A Super Earth:
The argument is that a Super Earth will have such a high surface gravity that it will trap an excess of hydrogen. Indeed, a planet with twice the radius of Earth will have eight times the mass of Earth. However this multiplication by 8 of its mass m is true if, and only if, the Super Earth has the same density as Earth. Earth has density 5.5, due to a heavy iron core with density 10. Silicate rocks have only density 3.
If a Super Earth had the same exact composition as Earth, doubling the radius r would change the surface gravity, which is proportional to: m/rr. If m is multiplied by 8 and r by 2, one sees that the surface gravity is multiplied by 2.
However, if the Super Earth is mostly made of Silicates, its mass will just be multiplied by 5, not 8. Thus its surface gravity will only augment by 25%.
If now one considers a super Earth with radius three times Earth, one sees it’s volume will be 27 times greater, but, if made mostly of silicates, its mass will be no more than 15 times greater. Meanwhile 1/rr is roughly 1/10. So the surface gravity, would be only 50% greater.
Thus one sees that Super Earths with surface areas roughly ten times Earth are imaginable.
One could argue that a huge metallic iron core is necessary to create a large magnetic field protecting against radiation, in particular solar storms which may strip the atmosphere (as happened on Mars). And thus one could insist that the preceding is unrealistic that way. But we are sitting next to a mighty yellow star. Red Dwarves, although subject to flares, thus capable of ejecting radiation, may, overall, be less corrosive than Sol (as their energy output is relatively tiny).
The best way to make sure that we cannot have habitable Super Earth is to construct huge telescopes… That means high taxes in the financial sector, that useless vampire (Reminder: Obama brought in all the guys who had deregulated FDR’s financial safeguards, under Clinton in the 1990s; FDR had put those safeguards in roughly 48 hours after becoming president in March 1933!)
A grander perspective: Why Is The Anti-Super Earth Crowd So Vociferous?
Ethan Siegel: “But if you insist on calling these worlds Super-Earths, the conclusion is inescapable: whether gaseous or rocky, a Super-Earth is no place for a human.”
I hope that considering my own logic, geophysical logic, Venus, Mars, the stridency of that conclusion is perceived to be unwarranted. Actually Laura Schaefer of Harvard thinks that surfing on Super Earths is definitively a possibility. According to her computer simulations, it’s easier to have oceans and they last longer (ten billion years) on Super Earths with 3 to 4 times the mass of Earths… http://news.harvard.edu/gazette/story/2015/01/surfing-on-a-super-earth/
Let’s comeback to the strident enemies of livable Super Earths: they suffer from a known malady. This is the usual problem: to become stars, or super-stars, super-scientists jump to unwarranted super-conclusions which are bound to becoming “trending” on the “social networks”. There is little difference between that general mood of people sure of “The First Three Minutes” (who was measuring time, then? “God”, Dog, or super-physicists?) and “Allahu Akbar” (who told them Dog was great, Dog Himself? A friend of theirs?)
This is the moral flaw of (super) tribalism, the “Will To Power”, hubris unbounded, the ardent desire to become top primate, Super Baboon: it flushes, with neurohormones any other worries, makes one feel as if one were god. They all want to be like Obama, get it all, presidency, right of life and death onto the world, multi-billionaire friends, Nobel, etc. Just to forget their pathetic little condition on the Third Rock from Sol.
Well, the deepest thinkers are made of sturdier stuff. Build those telescope, and search for livable Super-Earths. They are out there. Tax those financiers behind Forbes and all plutocrats. Or, rather, tax their robots: most orders in the financial markets are passed by robots which trade in a way that leads the markets: 90% of the robotic orders to buy or sell are cancelled before being enacted.
Build telescopes, not cynicism!