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Earth is the only planet we know of that harbors life. But could some exoplanets be even better for life?
“It just happened that in our own solar system, the Earth is the largest rocky planet.” Astronomer Dimitar Sasselov directs the Harvard Origins of Life Initiative and wrote the new book The Life of Super-Earths.
“Now we know that planets which are rocky but bigger than the Earth are plentiful, they’re around other stars in big numbers. And we certainly know that if you’re smaller than the Earth a lot of things go wrong. Your climate is less stable, your atmosphere can go away, like Mars, plate tectonic activity and chemical enrichment goes away as well.
“The Earth is great. But if you’re a little bit bigger than the Earth, all those things are the same or even better—more active, more chemistry, more stability—and nothing is worse. That you have a little bit higher G? That’s not a big deal, especially for the microbes.”
—Steve Mirsky
[The above text is a transcript of this podcast.]
[Look for the full interview with Dimitar Sasselov on an upcoming edition of the Scientific American Science Talk podcast.]
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10 Comments
Add CommentBigger Earths would be great for microbes, but one of the critical elements for making the Earth suitable for the development of complex life is the stability provided by its relatively large core, rotation, axial tilt and seasonal 'gyroscopic' stability provided by its single large moon.
Reply | Report Abuse | Link to thisCan complex life be expected to form on any planet that does not possess comparably moderated seasonal environmental stability? There have been times in Earth's past and likely its future when things weren't always so pleasant...
Don't believe the hype. Mars didn't lose tectonics because it was small, it lost them because her nuclear core either burned out or wasn't there. Venus is smaller than Earth, yet has an actively reducing crust and an abnormal helium-4 content in its atmosphere. Venus and Earth are nuclear powered by natural pile-thorium-uranium georeactors at their cores, Venus absurdly so. Mars either never was, or isn't now.
Reply | Report Abuse | Link to thisAside from that, superearths will, because of their increased surface gravity, shrink the maximum egg size they can support. This may have serious implications for both the young and the maximum size of terrestrial megafauna. Of course, life always finds a way.
For complex life, the energy requirements will rise proportionally with surface gravity. All things being equal, I could very easily see complex life having a much tougher time on a superearth.
Additionally, if you've got a compromised immune system, you'd find microgravity to be a boon to your recovery rate, while the pathogens don't notice much of a difference. Taking this to its linear conclusion, infections and disease will likely strike complex organisms harder on superearths.
In closing, I find myself chiding Mister Sasselov for relying on such a small sample size, that being the major rocky bodies of the Solar System. In the future, we will look back at all the predictions based on our own star system and laugh at how idiotic they all were. I can still remember being taught that gas giants naturally tended to form further from a star, before they started finding hot jupiters.
We must remember, up until a few years ago, we still thought that rocky bodies TENDED to form closer to the parent star (even disregarding the many MANY rocky moons).
The best place to find signs of sentient life in the galaxy will always be Sagittarius A*. There's nothing else in the galaxy you could possibly class as a better rally point than the stars orbiting that.
Well put, at least up to the last paragraph. You do know that Sagittarius A* is thought to be the location of the Milky Way's supermassive black hole, and that stars in that region follow wildly elliptical orbits around it, don't you? Doesn't seem like a very pleasant neighborhood to grow up in...
Reply | Report Abuse | Link to thisThis hypothesis falls apart immediately: life is anti-entropic and it would take larger energy availability to sustain any activity. Higher gravity means higher friction and that means higher heat generation. Tough enough to model carbon-based life without adding a whole new thermodynamics to the picture. When signals made by intelligent life are detected from "super size" rocky planets, I'll become a convert but not before.
Reply | Report Abuse | Link to thisWell put!
Reply | Report Abuse | Link to thisPerhaps someone's thinking of giant amoebas - that'd be cute!
As you know, our planet became more populated by more than seven billion inhabitant. This may make the life more difficult.
Reply | Report Abuse | Link to thisNowadays, because of promoting, new different lives, technologies,... etc, we need more sources to use. As usual, we've gotten our goods from the Earth since first human life. So far, this beautiful planet, was the best friend for us. Nevertheless, it's sources will ran out soon. Like oil or other things. frankly, we have too say goodbye to it,even if it supply our requirements just like before because now it's passing it's last Centuries.
In the meantime, other bigger rocky planets are more helpful than the Earth. I opine that, changing planet is considered for next generation.
Unfotunately, unless 'we' can figure out how to get up to 9 billion people to a better 'New World', this 'solution' dooms most of us to suffering the consequences of our irresponsible overpopulation of this planet.
Reply | Report Abuse | Link to thisTo me,first of all we have to manage our NATURALRESOURCES and use less from them and then think about other planets.Because az you know going to another planet needs a lot of tecnology,money,fuel and other things.So az it seems it's too expensive and also these big rocky planets are too far away.The people of future might be able too reach these planets.But in our time we just can economize and by that we can have a better weather and more sourses.so won't need a bigger planet.If you ask why we have to economize?I will tell you that:"we can't make the earth bigger to have a better climate and lands and sources to live better and going to another planet is impossible too and that's why we have to economize".
Reply | Report Abuse | Link to thisHow ever big planets doesen't have a lot difference.On the other hand they are not prepaired to live on them.The only planet that has water in it near here is just the earth.We can have a nice life in our beautiful planet.
So please try to protect it.
Origin and nature of Earth life, an update:
Reply | Report Abuse | Link to thisLiberate your mind from concepts dictated by religious trade-union AAAS.
Life is just another mass format + re-comprehend natural selection + natural selection is ubiquitous.
Life Evolves by Naturally Selected Organic Matter
I.
Homegrown Organic Matter Found on Mars, But No Life
http://news.sciencemag.org/sciencenow/2012/05/homegrown-organic-matter-found-o.html?ref=em
II. EarthLife Genesis From Aromaticity/H-Bonding
http://universe-life.com/2011/09/30/earthlife-genesis-from-aromaticityh-bonding/
September 30, 2011
A.
Purines and pyrimidines are two of the building blocks of nucleic acids. Only two purines and three pyrimidines occur widely in nucleic acids.
B.
Pyrimidine is a heterocyclic aromatic organic compound similar to benzene and pyridine, containing two nitrogen atoms at positions 1 and 3 of the six-member ring.
A purine is a heterocyclic aromatic organic compound, consisting of a pyrimidine ring fused to an imidazole ring. Purines, including substituted purines and their tautomers, are the most widely distributed kind of nitrogen-containing heterocycle in nature.
Aromaticity ( Kekule, Loschmidt, Thiele) is essential for the Krebs Cycle for energy production.
C.
Natural selection is E (energy) temporarily constrained in an m (mass) format.
Natural selection is a universal ubiquitous trait of ALL mass spin formats, inanimate and animate.
Life began/evolved on Earth with the natural selection of inanimate RNA, then of some RNA nucleotides, then arriving at the ultimate mode of natural selection – self replication.
Aromaticity enables good constraining of energy and good propensity to hydrogen bonding. The address of Earth Life Genesis, of phasing from inanimate to animate natural selection, is Aromaticity.Hydrogen Bonding.
Dov Henis (comments from 22nd century)
http://universe-life.com/2012/02/03/universe-energy-mass-life-compilation/
tags: life genesis, natural selection,
Earth Life
Reply | Report Abuse | Link to this- Earth life is just another naturally selected mass format.
- The primal base organisms of Earth life are the genes, i.e. the RNA nucleotides.
- All Earth life formats are progenies of genes evolution.
- Genomes are organisms evolved, and continuously modified, by the genes as their functional templates.
- Genetics is a progeny of culture, which is reaction to circumstances.
- The drive and goal of evolution of ALL mass formats is to enhance their energy constraint, to postpone their reconversion to energy, which goes on at constant rate since the Big Bang.
Dov Henis (comments from 22nd century)
http://universe-life.com/