With its current atmosphere, Mars has daytime temperatures above 0C just about every day in the equatorial regions. In sunshine, the solar panels temperatures can go up to 30C. But at night it goes below the temperature of dry ice, even in the Martian "tropics" many nights of the year.
So it's more the average temperature rather than the hottest temperature. Same in Antarctica though not nearly extreme - can be warm in sunshine in summer - but average temperature is very cold. Antarctica recently recorded a summer temperature of a record breaking 17.5 C Antarctica Recorded Its Hottest Temperature On Record This Week
But Mars gets hotter than that. But also far far colder.
Also - it has a very shallow permafrost. Over entire surface, the temperature is below 0C just a cm or two below the ground - it would be a totally white planet if it weren't that it has lost nearly all of its water.
This means that Mars can have liquid water right now. The main problem is not the temperature but the pressure. Double its atmospheric pressure - as probably happens when its axial tilt changes - and you should get liquid water flowing on the surface. And there's evidence of gullies formed by liquid water in the geologically recent past.
Right now, then there may well be liquid water on Mars also. It can from in various ways including on the interface of salt and ice - the "swimming pools for bacteria" of Nilton Renno's team.
Add salt, and salty brines are stable on Mars at low temperatures - and there's been indirect evidence for this for some time - recently Curiosity pretty much proved, though indirectly still, that there is cold liquid brine below the surface in sand dunes that it drove over, at night.
The big question is now, not whether liquid water forms on Mars as that is pretty much conclusively proved - also with the recent evidence of the warm seasonal flows. But is it habitable water? The water Curiosity found cycles through the day and some of the time is warm enough for life but too salty, they think, and other times, had enough water mixed in the salt for life but too cold. Can any of the water on Mars be liquid and also unsalty enough for life, and also warm enough?
Mars already has a 1% of Earth atmosphere CO2 atmosphere, more than we have on Earth. If we gave it an Earth atmosphere, magically, just wave a wand and it instantly has an atmosphere like Earth - well it would have less CO2 which would cool it down - though more water vapour which would warm it up. The oxygen and nitrogen wouldn't help at all. End result is that it would still be very cold, too cold for trees to grow in the tropical regions there, for instance.
Even with a dense CO2 atmosphere, it's hard to have unfrozen oceans apparently. It might have had mainly ice covered oceans in the early days. Its orbit varies a lot unlike Earth, sometimes close to circular, sometimes a bit elliptical as it is now, and sometimes it has a very eccentric elliptical orbit. One idea is that perhaps its ocean was liquid when it had more eccentric orbits, and only when it was closer to the sun. Perhaps it kept freezing over for half of its orbit. (I.e. alternating an Earth year of liquid ocean with an Earth year frozen over, say roughly).
But basically they are still working on this, trying to figure out how to model the early Mars oceans. It's harder to get a liquid ocean than to get temporary floods.
Maybe it was warmed by small amounts of methane as a greenhouse gas. Mars ocean hypothesis - theoretical issues
For more on this,
So it's more the average temperature rather than the hottest temperature. Same in Antarctica though not nearly extreme - can be warm in sunshine in summer - but average temperature is very cold. Antarctica recently recorded a summer temperature of a record breaking 17.5 C Antarctica Recorded Its Hottest Temperature On Record This Week
But Mars gets hotter than that. But also far far colder.
Also - it has a very shallow permafrost. Over entire surface, the temperature is below 0C just a cm or two below the ground - it would be a totally white planet if it weren't that it has lost nearly all of its water.
This means that Mars can have liquid water right now. The main problem is not the temperature but the pressure. Double its atmospheric pressure - as probably happens when its axial tilt changes - and you should get liquid water flowing on the surface. And there's evidence of gullies formed by liquid water in the geologically recent past.
Right now, then there may well be liquid water on Mars also. It can from in various ways including on the interface of salt and ice - the "swimming pools for bacteria" of Nilton Renno's team.
Add salt, and salty brines are stable on Mars at low temperatures - and there's been indirect evidence for this for some time - recently Curiosity pretty much proved, though indirectly still, that there is cold liquid brine below the surface in sand dunes that it drove over, at night.
The big question is now, not whether liquid water forms on Mars as that is pretty much conclusively proved - also with the recent evidence of the warm seasonal flows. But is it habitable water? The water Curiosity found cycles through the day and some of the time is warm enough for life but too salty, they think, and other times, had enough water mixed in the salt for life but too cold. Can any of the water on Mars be liquid and also unsalty enough for life, and also warm enough?
Mars already has a 1% of Earth atmosphere CO2 atmosphere, more than we have on Earth. If we gave it an Earth atmosphere, magically, just wave a wand and it instantly has an atmosphere like Earth - well it would have less CO2 which would cool it down - though more water vapour which would warm it up. The oxygen and nitrogen wouldn't help at all. End result is that it would still be very cold, too cold for trees to grow in the tropical regions there, for instance.
Even with a dense CO2 atmosphere, it's hard to have unfrozen oceans apparently. It might have had mainly ice covered oceans in the early days. Its orbit varies a lot unlike Earth, sometimes close to circular, sometimes a bit elliptical as it is now, and sometimes it has a very eccentric elliptical orbit. One idea is that perhaps its ocean was liquid when it had more eccentric orbits, and only when it was closer to the sun. Perhaps it kept freezing over for half of its orbit. (I.e. alternating an Earth year of liquid ocean with an Earth year frozen over, say roughly).
But basically they are still working on this, trying to figure out how to model the early Mars oceans. It's harder to get a liquid ocean than to get temporary floods.
Maybe it was warmed by small amounts of methane as a greenhouse gas. Mars ocean hypothesis - theoretical issues
For more on this,
- Might there be Microbes on the Surface of Mars?
- Why Mars Surface Life May Leave No Traces In Its Atmosphere: Our Rovers May Need To Go Up Close To See It
- Are There Habitats For Life On Mars? - Salty Seeps, Clear Ice Greenhouses, Ice Fumaroles, Dune Bioreactors,...
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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