I hear tell that scientists have discovered a planet in the ‘Goldilocks Zone’ of another sun. Not too hot, not too cold, just right.
But it has five times the mass of Earth, and so five times the gravity. (Right?)
Presume that this planet is favorable for life, make the best case for me. What would such a planet be like? How would water behave? Chemical reactions? Plate tectonics? Life?
Consider Krypton. Higher gravity induces super-strength, flight, and x-ray vision.
(I actually don’t think 5gs is enough to change chemistry, although land-dwelling living things will probably be more robust structurally that Earth analogues.)
Here on earth, a lot of larger organisms are limited by gravity. The tallest trees can’t grow any more, since they have to maintain an unbroken chain of water from root to leaf tip. With 5x the gravity trying to pull that column of water apart, earth trees would only grow to 1/5 the height. Land animals would be similarly limited, since bones or exoskeletons that can support life here on earth would be prohibitively heavy to support a similarly sized creature at 5 g.
I don’t think basic chemistries would be changed by higher gravity. It wouldn’t directly affect anything floating in an ocean.
Don’t think so. More to it than just that. Consider the Moon. 1/80 mass of Earth, 1/6 gravity. Mars: 1/10 mass of Earth, 1/3 gravity.
(Wrong.) Assuming it has roughly the same density as earth, surface gravity will be about 1,7 g.
It wouldn’t be 5 Gs so it probably wouldn’t be 1/5. I don’t think it’d be 1/5 anyway, actually. Gravity does weird things to water weight, meaning that the bottom of that column of water would exert a lot of force on the tree itself, and be very dense.
But there likely wouldn’t be standing/stable oceans on this planet. It’s tidally locked, and close, so we’re probably talking a habitable band, not the entire surface. Probably lakes, rivers, maybe a sea or two from glacial melt (which would be constant on a tidally locked planet).
A planet five times more massive does not necessarily have a 5g gravity field at the surface; gravity also depends on the density of the planet (though if it is a rocky crust with an nickel-iron core, it is probably close). A 5g surface field won’t alter any fundamental chemistry per se, although the strength of the field at the surface may result in greater differentiation between fluids (and especially gaseous fluids) of differing densities in the same way that a laboratory centrifuge separates out substances in a colloidal solution. It may also change the rates of reactions that are influenced by gravity, and of course fluid dynamic behavior in general. Surface, water, in particular, would behave in nearly the same fashion as it does at 50 meter depth in an ocean or deep lake. Water suspended in atmosphere probably can’t form as large a droplets as it does in Earth’s atmosphere before falling, though that depends on the particular formulation and density of the atmosphere.
One would also expect an otherwise Earth-like atmosphere to be roughly five times denser at the surface, which itself is no handicap–creatures live and thrive in the ocean under similar pressures–but we would also expect the atmosphere itself to be thicker, possibly filtering out more solar radiation, which may significantly reduce the amount of solar energy available to photosynthetic organisms if the spectrum and radiation flux of the planet’s star at its orbit is comparable to Earth. I would suspect that any life might tend more toward a chemoautotrophic form (using environmental chemical energy rather than photoenergy from the star as nearly all Earth lifeforms do in some fashion). Life might also tend to form up in the atmosphere rather than on the surface, especially if the atmosphere is thicker than Earth’s. Surface life, if it existed, would likely move much slower owing to the greater energy requirements for locomotion, and would likely be much shorter, not only because of the higher structural load with height but because of liquid transport limitations; anything taller than about two meters would require capillary action or transpirational pull rather than direct pumping of fluids.
In general, it is hard to say what life on a planet with such gravity would be like, because there are so many other factors that go into play with both planetology, but it would be dramatically different from life on Earth.
Stranger
Well, how could we determine the mass of this extra-large planet? We ought not to get too excited until we determine if the local gravity is also in the Goldilocks Zone.
They could determine its mass by seeing how much it was tugging on its host star.
I think more important then its mass in determining whether the planet has an atmosphere so it can hold onto its water is what kind of core does the planet have?
I imagine, at 5X Earth mass, it should have a liquid core. A liquid core means it has a strong magnetic field, which would keep the atmosphere from blowing away. That’s just a guess, though. I’m sure a real planetary geologist would have a better idea.
The mass of the planet is known, at least as a lower limit (since the Doppler effect deduction method doesn’t yield more than that) – it’s about three times that of the Earth (here’s the MPSIMS thread on its discovery). If you meant its density (and by extension, volume and surface gravity), I believe we can only extrapolate from current models based on observations within our solar system, which tell us more or less that it’s probably around Earth’s density, perhaps somewhat less than that (IIRC, Earth is the densest of our solar system’s rocky planets). That’d give a surface gravity of about 1.5 g, which is a bit of a workout, but doesn’t impose too severe restrictions on habitability, I imagine.
F = GMm/R[sup]2[/sup], people.
It depends on the size of the planet as well as the mass (hence why the density)
That’s an article from The Washington Post on the discovery.
Awesome.
37-day orbit? Christmas every month! Sign me up…
You’ll love it till you realize all the birthday presents you’d have to buy. Even more so once you notice that, due to the tidal locking, each rotation around the star also corresponds to one (sidereal) day…
It is very close to the sun but the sun is low powered.
It also seems it is tidally locked to the star so one side always faces the sun. As such the habitable zone on the planet would be where it is perpetual sunrise/sunset.
I wonder what the weather is like there? Very hot on one side, very cold on the other, I imagine there’d be hurricane force winds circling the planet. Probably not a nice place but then I really have no idea.
An article I read said the planet is 3x the mass of the earth.
I wanna send a probe! This is neat! Heck - if we built a probe on the old “Orion” design (set off nukes behind a giant pusher-plate for acceleration), it’s not crazy to hope we could hit maybe 5% of light-speed. (Especially if we’re willing to settle for a flyby, not orbital insertion, so we don’t need to worry about carrying fuel - bombs - for deceleration). That gets us to Gliese581g in, what, 200 years? Heck, people used to spend 100 years just building useless cathedrals - and we wouldn’t need to spend more than maybe ten, twenty years actually developing and building our interstellar probe. I mean, we already know in theory how to build an Orion-type ship, we know how to build rovers and land them - the only really tricky bit is making sure the probe could operate autonomously and actually send a signal back to Earth.
ETA: Actually, if we only went for a flyby, there’s no way we could land rovers - rovers hitting planets at relativistic speeds go smash.
Funny thing - when we had a thread asking what our reactions would be to finding life on Mars, my thought was “meh”. But perhaps I’m not as good a judge of my own character as I thought - this is really cool!
Gliese581g or bust!
Needs a cooler name, though. Any thoughts?
Bad Astronomy, as always, has an excellent article answering all your questions.
You’ve been beaten to it:
20+ light years away. How long would it take the fastest probe we could launch say in 10 years with the best tech we have (or are likely to have then)?
I’m guessing something disappointing like centuries…
Gah, answers appeared before I submitted.
Absolutely agree with the cathedral quote above. We’ve spent centuries pursuing much lesser goals.