What consequences could a higher surface gravity have on life and geological evolution?

Question

I am trying to build a world which has a bit larger gravity force than earth, 1.25g. And I was wondering which impact could this have on its geology and life evolution.

I think that with a higher gravity two things would be true:

• No flying species, because it would be harder to lift of the ground.
• No big mountain ranges. Maybe the higher altitude of a mountain would be around 3000 meters.

Maybe most animals would be relatively short but very robust, so they can support the weight. Compared to earth life form they would be slower but much stronger.

What do you think?

Asumptions:

• The Atmosphere composition is similar to Earth
• The Star is similar to Sun
• The Planet has a moon big enougth to keep its axis stable
• The Planet is a bit closer to its star, so its hotter, but not too much (0,9 AU)

Answer 1

There will be significant differences between the earth and your planet.

25% of additional gravity means 25% additional mass, but only about 10% additional radius. Thus, the atmosphere will be denser and there will be more water on the planet. I don't have a planet simulator ready to decide whether your planet (closer to the sun) will come out as a hot Earth of a cooler Venus, let's assume a hot Earth.

Sea level will be higher (just because there is more water available, but the surface has not grown proportionally). Your planet will consist of chains of islands (representing the hills and mountains). The land/sea ratio will be much smaller than on Earth. There will be lots of heavy tropical storms.

The will be no ice caps at the poles.

Land bound life forms will be less sophisticated than on Earth (no stable continents, but only rather short-lived islands support them) and probably be able to cross the water (either swimming or flying). Maybe you have some kind of air-breathing flying fish filling the evolutionary niche of birds.

There are 25% more radioactive elements inside the planet, but the surface has not grown proportionally: The geological activity of the planet is probably higher than on Earth.

I agree with the other posters that increasing the amount of gravity will not have significant influence on biomechanics, all kind of body shapes that work on Earth will also work on your planet. When there are kind of reef-building corals, your planet will have lots of atolls.

Answer 2

I don't think that 25% of our gravity make such a big difference.

There still probably would be birds and other flying creatures, although with stronger wings.

There still would be mountain ranges, and even ones that exceed the heights of Terran mountains would surely exist - geological forces operate very slowly and are very powerful, which means that changes in gravity usually don't really affect the structure of the planet.

However, your atmosphere may be a little bit more dense, which could strengthen erosion.

Answer 3

I don't think you'd see a significant change in shapes overall - you'd still have spindly-legged mouse and thick-legged elephant analogues, but they'd both be smaller than their Terran counterparts.

Flight should still be possible - higher gravity means a denser atmosphere, which should balance out the gravity.

There would be some slight differences if you placed them next to Earth life, but I think you can assume the same evolutionary pressures would occur as on any other Earthlike alien world.

Answer 4

Well mountain ranges would likely be smaller, but not that much smaller. There certainly wouldn't be anything as tall as Everest. On Earth, the current max is around 10Km, increasing gravity to 1.25 I would make a rough guess of about 8km. You can play with the formulas here if you want a more accurate number.

As far as flying animals. That change is certainly not enough to stop flying animals. It might reduce the numbers of species that fly however. One of the things that might help balance out the gravity pulling down, is a stronger gravity could help increase the air density, allowing for easier lift. I would guess more species would be gliders, like the albatross or vulture.

As far as everything else, it would be very similar to what we have available, with sizes being slightly shorter and and squatter. Skeletal systems will need to be stronger and denser to handle the extra stresses. And of course muscle systems will need to be stronger.

Gravity also plays a roll in how tall trees can grow, because of capillary action and how high it can move water up the trunk.

But overall, a %.25 increase in gravity wouldn't be terribly different to what we have now.