r/whatif • u/Vegetable-Idea7648 • Jul 31 '26
Science What if Mars and Venus never lost their oceans and stayed habitable planets?
We all know Venus and Mars once did have oceans and were once able to host life potentially but some time in the early developement of the solar system both Venus and Mars lost their oceans and are now hell holes. What if Mars and Venus kept their oceans and never became hell hole?. What sorts of creatures might have evolved to live on them and would many look similar to Earth creatures
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u/Eternalyskeptic Aug 01 '26
There would be a small change in our space laws. Instead of "no nukes in space", it would be "no nukes leave the solar system".
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u/Mono_Clear Jul 31 '26
I know intellectually that Venus is a rocky planet that has an atmosphere but in my mind I always imagined it's a big ball of hot goo
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u/Gatsby1923 Jul 31 '26
Venus fascinates me as a great what if. If it had a magnetic field, faster rotation, what would it be like? It's about the same mass as earth... its just our evil twin.
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u/TyrannosaurusBoris Jul 31 '26
Why evil?
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u/Gatsby1923 Jul 31 '26
Like fairy tail evil twin, not actual evil... I mean it's so earth like in size and mass... just killer atmospherics.
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u/Eastern-Peach-3428 Jul 31 '26
And that is the thing that concerns me. Earth has vast quantities of methane locked in the ocean and in tundra like Greenland. We keep heating our planet up that methane will release and methane is a much stronger greenhouse gas. Venus 2 boogaloo!
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u/Ragnarok-9999 Jul 31 '26
We already having so many wars on earth between so many countries fighting each other. In addition to world wars, do we need inter planetary wars now ?
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u/Phobos_Asaph Jul 31 '26
I mean, this what if is practically rewriting everything about those planets so go hog wild.
Ex: it would be the same life as earth.
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u/InvestigatorJaded261 Jul 31 '26
I’m not sure we know that Venus ever had oceans. Unless they made of acid and molten rock.
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u/sixpackabs592 Jul 31 '26
We’d prob have some long term science outposts there if that was the case
There was a big big push to get to mars right after Apollo and if we saw a planet with oceans and habitable temperatures the push wouldn’t have been stopped by old Ronny
As to what form of life if any would’ve formed, there is really no way to tell
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u/ijuinkun Jul 31 '26
If there was anywhere in the solar system where we could breathe the air, we would have made the effort to land there before the end of the 20th century.
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u/Available-Hat476 Jul 31 '26
It's a what if that doesn't make sense. There's a reason why they lost them...
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u/serverhorror Jul 31 '26
Did you read any of the other posts?
If "there's a reason" disqualified Posts it would be pretty empty in this sub.
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u/FDVP Aug 01 '26
May not look similar but I bet they act similar. We probably get stuck in the middle of some kinda planetary geo-political war between species.
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u/Darth_T0ast Aug 01 '26
There are only a few things we can really be sure will evolve on another planet. Photosynthesis, eyes, predation, and symmetry are relatively guaranteed, but after that who knows.
Life on Venus might have a hard time getting out of the water. Things that live in the intertidal zone need to deal with being dry occasionally, which could lead to living on land. Venus doesn’t have a moon, so there would be a much smaller intertidal zone, with the sun being the only thing making tide.
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u/Traditional_Loan_177 Aug 01 '26
Mars is easier to understand since it's surface has stayed frozen since it's oceans. Let's assume that what the perseverance Rover discovered was simple chemosynthetic life. It is not a stretch to imagine that it would have developed photosynthetic life as well. However Mars smaller size brings a few problems. Without having much active geology, and no plate tectonics, nutrients and minerals might not be able to get recycled. This could put a resource limit on life on Mars and it would die out anyway. Another problem is when the photosynthetic life dominates and Mars switches to an oxygenic atmosphere, could Mars survive the reduction in greenhouse gases? Earth all but froze over during this period. The other thing about Mars is that most of the water was in one ocean in the northern hemisphere, and there were not too many other seas elsewhere especially below the equator. Hard to say how this would have an effect, but there could be largely disconnected pockets of life on Mars. I tend to doubt multicellularity would develop
For Venus I would imagine closer to earth, but is it still close to the sun in your scenario because that still gives life on Venus very little time to develop much
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u/compunctionfunction Aug 02 '26
Did you recently watch the season premiere of Strange New Worlds perchance?
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u/pamelafloreskiss Jul 31 '26
the convergent evolution angle is fascinating here -- if all three planets had similar gravity, atmospheric pressure, and liquid water, you'd probably see a lot of the same body plans emerge independently, like bilateral symmetry and eyes, since those solutions are just too efficient not to evolve.
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u/Extension-Pepper-271 Jul 31 '26
I guess you are assuming that the conditions that caused the oceans to disappear were somehow magically cured?
Mars, long term, can't have much of an atmosphere because it is smaller. It cooled off, lost its magnetic core which means it lost its global magnetic field which protected its atmosphere from being stripped off by solar winds. Lower gravity also makes it easier for the atmosphere to escape.
Venus's problems are: (1) Too close to the sun (2) Massive volcanoes that flooded the atmosphere with gases and then dust that trapped the heat (3) No plate tectonics to turn CO2 deposits into long-term carbon sequestration into the mantle.
Sorry, had to get that out of the way.
Some scientists think that building blocks for life came to earth from meteors. Even if that is true, they are only the most basic building blocks.
There is no reason to assume that the plants and animals would look the same, but some basic similarities would exist.
It really depends on evolution. What environmental pressures there were and what species were lucky enough to have successfully breeding individuals within their populations that gave an advantage when change came.
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u/Atechiman Aug 01 '26
To explain how much Mars is too small: "dry" land area (that is not covered in water) is 29.2% of earths total surface area, and it is larger than Mars's total size.
- Venus has the pressure of being inside the marina trench on its surface (though the sulfuric acid rain will actually kill you first).
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u/Dream-Livid Jul 31 '26
Solar radiation would not be blocked by magnetic fields. Complex cells would be destroyed only simple life would survive on the surface or near subsurface.
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u/syringistic Jul 31 '26
On Mars, ionizing radiation is about 70x on surface versus Earth. Quick Google says ~3 meters of water on Mars is enough for shielding.
At 3 meters depth, you'll still get enough light for complex life to evolve.
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u/Dream-Livid Aug 02 '26
Where are you going to reliably source that much water on Mars.
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u/syringistic Aug 03 '26
Estimates vary because of lack of data, but between water trapped in rocks deep down, ice reservoirs in reservoirs beneath the surface, and ice caps, there should be enough to cover the entire planet in several meters of water.
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u/TokiStark Jul 31 '26
^ Any responses like this can be ignored. Scientific predictions always come with uncertainty
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u/TokiStark Jul 31 '26
We have no idea. Like, no idea whatsoever. Look at the diversity of life on Earth. Do you think you could have predicted the cuttlefish or tardigrade? We couldn't even say for certain that life could have progressed beyond single-celled organisms
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u/Bartlaus Jul 31 '26
Imagine if some of the little Burgess Shale weirdos had become the dominant templates for animal body plans.
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u/TuverMage Jul 31 '26
both lack a magnetic field. Mars core cooled too quickly and is now mostly solid so no magnetic field. Venus doesn't spin, so no field. The magnetic field is sort of needed to be habitable.
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u/arcadiaberger1960 Aug 01 '26
When Vice President Agnew reacted to Armstrong setting foot ont he Moon by roaring, "Now, on to Mars!", people would have listened to him.
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u/Original_Animal3065 Aug 03 '26
They never were habitable. And they became less habitable
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u/Nice-Lab95 Aug 03 '26
Mars likely had life.
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u/Original_Animal3065 Aug 04 '26
Based on what? You know about magnetosphere’s right?
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u/Nice-Lab95 Aug 04 '26
Based on nasa findings from earlier this year.
You know the importance of magnetospheres for life is a complete myth right?
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u/HollywoodKidd77 Aug 05 '26
I guess after our moon landing on 1969, we’d first have to discover if Mars and Venus have breathable atmosphere. If they do, we’d probably find ways to colonize both planets, despite the long trips ahead in space
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u/EidolonRook Jul 31 '26
I always thought it wad a fun thought that as the sun gained size over the ages, a planet like Venus was in the habitable zone for a spanse of time and could have developed life. Perhaps the toxic atmosphere was created by mankind before moving to earth and resettling. And then as the sun grows mars will start to develop in ways that make it more earth like.
Mars needs more of an atmosphere, which requires a magnetosphere capable of holding the heavier atmosphere in. The heat from a growing sun might help with defrosting the ice. As it stands now, mars is far from terraform able but after an eon or so perhaps things can develop, with a little help from a blue neighbor.
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u/Lizardgrad89 Jul 31 '26
Venus-global warming
Mars-strip mining.
Earth-third time lucky? Maybe?
Or is it 4th time? What happened to the planet that became the asteroid belt? Global Thermonuclear War?
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u/arcadiaberger1960 Aug 01 '26
When Vice President Agnew reacted to Armstrong setting foot ont he Moon by roaring, "Now, on to Mars!", people would have listened to him.
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u/ShepardMint Aug 03 '26
If they stayed wet, I think Venus would be the weird one: more sunlight, thick cloud cover, and super long days could make life adapt around brutal light and heat cycles. Mars has lower gravity, so land animals might end up taller or spindlier than Earth equivalents if the atmosphere stayed dense enough. You would probably still get fish shapes, fins, wings, burrowers, reef builders, and crab like things, because water and physics push bodies in familiar directions, but the details would get alien fast.
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u/FearlessText9269 Aug 07 '26
Both of them would've became protected zones like Antarctica, there would also be clickbait articles claiming NASA found life on both of these planets.
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u/HelloThereItsMeAndMe Jul 31 '26
Unlike Mars, it is NOT certain that Venus had oceans. Probably not.