Anyone serious about terraforming Mars would have to address the lack of a magnetic field. The weaker gravity on Mars is not enough to hold an atmosphere in place. You could pump all of that CO2 into the atmosphere, and it would just blow away in a few years.

Not certain, but I believe the time frame on this is not nearly so dire. The loss of a terraformed atmosphere would occur in the “blink of an eye” in cosmic terms, but in human terms that should be several thousand years at least, if not a million or so, and that should be plenty of time for the purposes of hypothetical colonization efforts.

Much might depend on the actual rate at which a terraforming attempt adds gas to the atmosphere. (So long as one adds gas to the atmosphere faster than the gas is lost, one can maintain a thicker atmosphere as long as one has the resources to do so).

Dunno how modern diversity data holds up there though.

@ Patrick:

“How would you get the surface to support heavy flowing water?”

Primarily by changing the rate of water evaporation. Water evaporates fast in a vacuum; on Earth not so fast.

@ Doug:

“all planets are moving away from the sun”

Refs please. Orbits aren’t stable over time, so rates aren’t either.

@ Georg:

Orbital tilt affects climate. Milankovitch theory is claimed to predict cycles well, but are less understood. “Obliquity is a major factor in glacial/interglacial fluctuations (see Milankovitch cycles).” [Wikipedia.]

Milankovitch was an engineer; climate scientists have adopted his theory AFAIU.

@ Jay Fox:

“Without this field, there is no way to maintain an atmosphere of sufficient pressure to allow surface water in liquid form.”

That depends on the original atmosphere, the sun and the distance to it. Earth looses 2/3 of atmosphere to solar CMEs; there are other leakage processes.

“You could pump all of that CO2 into the atmosphere, and it would just blow away in a few years.”

If by “a few years” you mean millions of years, perhaps. The current atmosphere has lasted long… though it started out denser, natch.

“The stability provided by a massive moon like ours is what makes life so diverse on earth.”

There is no such theory in biology. Diversity is a not an understood process, but it mainly results from multicellularity.* That means we would see roughly the same diversity with or without moon (tides; stabler climate).

If anything the relatively stable climate may keep diversity down – and tides increase it. But again, this is an open area of research.

“methane continues to enter the atmosphere.”

Another open area, AFAIU. Scientists revisiting observations claim IIRC that it is simply our atmosphere that has been detected (astronomy observations) respectively uncertain effects (orbiter observations).

The simplest hypotheses is primarily no methane, and if there is that it is volcanic.

[* Which in turn mainly is a result of eukaryote endosymbiosis, giving our cells 4-6 order more energy to turn around proteins that prokaryotes. Thus enabling maintaining and utilizing a large genome.

It is an interesting area, since while endosymbiosis happens in prokaryotes too (but much more often in eukaryotes) mitochondrial endosymbiosis happened only once.

It is relatively rare, so diversity (multicellularity above and beyond the feeble attempts of some bacteria) will be rare too. Maybe ~ 30 % of ~ 5 Gy old habitable planets, assuming 100 % of them have life, both figures from assuming Poisson attempt models for abiogenesis and endosymbiosis respectively.]

Also a fun fact I should verify but I heard it at a talk a few years back. If you evaporated all the water on the earth, it would be super critical steam. They were doing modeling of extrasolar planets and were wondering if the amount of water on a molten planet has some upper limit. I really should hunt that paper down.

Here the volume of the Earth’s water is 1.332×10^9 km^3, supercritical steam has a density of 0.322 g/cm^3, so the volume would be ~4.1 x10^9 km^3. The effective volume of the Earth’s atmosphere is ~4.2×10^9 km^3. Of course the volume of the atmosphere is debatable since the pressure varies with altitude and where the end is, but it’s within an order of magnitude and something to ponder when thinking about early planet evolution.

Thank you. Very interesting.

Mars being quite a bit smaller than earth, it cooled more quickly, lost it’s internal dynamo and the resulting magnetic field. Without this field, there is no way to maintain an atmosphere of sufficient pressure to allow surface water in liquid form.

Anyone serious about terraforming Mars would have to address the lack of a magnetic field. The weaker gravity on Mars is not enough to hold an atmosphere in place. You could pump all of that CO2 into the atmosphere, and it would just blow away in a few years. It would not stay around long enough to change anything, except the total amount of CO2 on the planet.

The axial tilt problem would really mess with seasons, albeit slowly. The stability provided by a massive moon like ours is what makes life so diverse on earth. The environment stays relatively stable long enough for the very slow process of evolution to take place. Instability is a major reason Mars is so barren. No stable magnetic field and tilt, weak gravity, and a thin, evaporating atmosphere all combine to make Mars what it is today.

The apparent evidence of early volcanic activity may also have been instrumental in what we observe today. There could have been enough material ejected into the atmosphere to produce a volcanic winter of sorts. Who knows what percentage of Mars’ history was blanketed in a volcanic cloud. It’s possible that this alone prevented advanced life forms from taking hold. There does appear to be some amount of microbial life and activity based on the fact that methane continues to enter the atmosphere. Given the history of the planet, it is possible that microbes are the only life forms capable of making a living in that harsh environment.

This will not happen all of a sudden! The pole wandering would lead
that the carbon dioxide from the former poles will sublimate to the
new locations. This would happen so slowly, that atmospheric presseure
would not be affected. What kind of amateurs (no, amateurs are better!)
make up such nonsense? Climate scientists?