https://twitter.com/MaxFagin/status/1583527411177508864QuoteNASA's Jim Green presenting on the concept of an artificial magnetic field at Mars-Sun L1 as a way to shield Mars from solar wind and halt Mars' atmospheric loss, so it can be terraformed "naturally". This idea keeps coming up, but I wish it didn't. I think it's a bad idea 🧵It's not that the idea doesn't work. Best I can tell, the underlying physics is sound, and a ~65 GW electromagnet at Mars-Sun L1 would indeed create a Mars sized magnetotail, reducing the loss of the atmosphere by a factor of ~1000 or more. That's not the problem.The problem is that a 65 GW L1 shield is a misalocation of resources. 65 GW is ~one Germany. I believe a Martian civilization will have that much power to spare someday, but there will *always* be better ways to use that much power *if* terraforming is the goal.Mars' atmospheric loss rate is only ~10 kg/day. Even if the loss rate goes up ~10,000x when the atmosphere is thickened, it still wouldn't be worth stopping; because applying that same 65 GW of direct heat to the regolith would liberate ~1,000,000 kg_CO2/day to the atmosphere.*CORRECTION*I types the atm loss rate as ~10 kg/day. Correct value is ~10 kg/*second*.But I did type the correct number into the calculation, so the tweet is in error, not the math.That 65 GW wouldn't be enough to terraform Mars on its own via direct CO2 liberation (still a ~100 million year process) but it would still be faster than the ~billion years it would take if we did stop the leak, and let Mars "naturally" replenish its atmosphere.Mars is a leaky aircraft carrier that takes ~billion years to sink. We can either:1) Throw a cup of water overboard every few years2) Use a fleet of helicopters to carry the aircraft carrier everywhere so it never touches the oceanAdding a magnetic field to L1 is solution 2
NASA's Jim Green presenting on the concept of an artificial magnetic field at Mars-Sun L1 as a way to shield Mars from solar wind and halt Mars' atmospheric loss, so it can be terraformed "naturally". This idea keeps coming up, but I wish it didn't. I think it's a bad idea 🧵It's not that the idea doesn't work. Best I can tell, the underlying physics is sound, and a ~65 GW electromagnet at Mars-Sun L1 would indeed create a Mars sized magnetotail, reducing the loss of the atmosphere by a factor of ~1000 or more. That's not the problem.The problem is that a 65 GW L1 shield is a misalocation of resources. 65 GW is ~one Germany. I believe a Martian civilization will have that much power to spare someday, but there will *always* be better ways to use that much power *if* terraforming is the goal.Mars' atmospheric loss rate is only ~10 kg/day. Even if the loss rate goes up ~10,000x when the atmosphere is thickened, it still wouldn't be worth stopping; because applying that same 65 GW of direct heat to the regolith would liberate ~1,000,000 kg_CO2/day to the atmosphere.*CORRECTION*I types the atm loss rate as ~10 kg/day. Correct value is ~10 kg/*second*.But I did type the correct number into the calculation, so the tweet is in error, not the math.That 65 GW wouldn't be enough to terraform Mars on its own via direct CO2 liberation (still a ~100 million year process) but it would still be faster than the ~billion years it would take if we did stop the leak, and let Mars "naturally" replenish its atmosphere.Mars is a leaky aircraft carrier that takes ~billion years to sink. We can either:1) Throw a cup of water overboard every few years2) Use a fleet of helicopters to carry the aircraft carrier everywhere so it never touches the oceanAdding a magnetic field to L1 is solution 2
I suspect that the 1000 tonnes/day of extra CO2 would be adsorbed back into the regolith and/or precipitate out again at the poles within a short period of time as the warmed gas radiated the excess heat into space.
If there were (hypothetically) a 1,000 square mile rectangle on Mars that was colder than everywhere else, you actually only have to warm up that one area to alter the equilibrium concentration of CO2.In the real world, of course, this 'rectangle' corresponds to the Martian north and south poles. Polar heating strategies (eg with orbital mirrors) therefore provide a disproportionate terraforming effect vs. evenly heating the entire surface.
Quote from: Twark_Main on 11/09/2022 12:38 pmIf there were (hypothetically) a 1,000 square mile rectangle on Mars that was colder than everywhere else, you actually only have to warm up that one area to alter the equilibrium concentration of CO2.In the real world, of course, this 'rectangle' corresponds to the Martian north and south poles. Polar heating strategies (eg with orbital mirrors) therefore provide a disproportionate terraforming effect vs. evenly heating the entire surface.No, releasing the permanent (southern) polar cap CO2 ice would give no significant "terraforming effect", or rather, greenhouse effect: e.g., the 8 m surface CO2 cap would add < 1 W/m2.Also, exposed and redistributed polar water ice would have high albedo relative to regolith: i.e., poor absorption of insolation energy.
Quote from: LMT on 11/12/2022 02:27 amQuote from: Twark_Main on 11/09/2022 12:38 pmIf there were (hypothetically) a 1,000 square mile rectangle on Mars that was colder than everywhere else, you actually only have to warm up that one area to alter the equilibrium concentration of CO2.In the real world, of course, this 'rectangle' corresponds to the Martian north and south poles. Polar heating strategies (eg with orbital mirrors) therefore provide a disproportionate terraforming effect vs. evenly heating the entire surface.No, releasing the permanent (southern) polar cap CO2 ice would give no significant "terraforming effect", or rather, greenhouse effect: e.g., the 8 m surface CO2 cap would add < 1 W/m2.Also, exposed and redistributed polar water ice would have high albedo relative to regolith: i.e., poor absorption of insolation energy.Why release the H2O, then? We're only interested in the CO2, and there's wildly differnt melting points. Aim for a point above the CO2 sublimation temperatue but not above the H2o sublimation temperature.
No, releasing the permanent (southern) polar cap CO2 ice would give no significant "terraforming effect", or rather, greenhouse effect: e.g., the 8 m surface CO2 cap would add < 1 W/m2.
Quote from: Twark_Main on 11/09/2022 12:38 pmIf there were (hypothetically) a 1,000 square mile rectangle on Mars that was colder than everywhere else, you actually only have to warm up that one area to alter the equilibrium concentration of CO2.In the real world, of course, this 'rectangle' corresponds to the Martian north and south poles. Polar heating strategies (eg with orbital mirrors) therefore provide a disproportionate terraforming effect vs. evenly heating the entire surface.No, releasing the permanent (southern) polar cap CO2 ice would give no significant "terraforming effect"
Quote from: LMT on 11/12/2022 02:27 amNo, releasing the permanent (southern) polar cap CO2 ice would give no significant "terraforming effect", or rather, greenhouse effect: e.g., the 8 m surface CO2 cap would add < 1 W/m2.Can you link to the actual paper, instead of the abstract? The abstract does not make any claims as to the value of cap CO2.
...sulfur hexafluoride has a boiling point of just -50 °C.Does this mean that if we build factories pumping out SF6 it will "rain out" over the poles?
...polar caps... act as the (level-setting) "cold traps" on Mars.
"The temperature gets so low, you start freezing the atmosphere onto the surface," said Sylvain Piqueux of NASA's Jet Propulsion Laboratory... "Once you reach that temperature, you don't get colder, you just accumulate more frost. So even on the polar caps, the surface temperature isn't any colder than what these lower-latitude regions get to overnight."
Quote from: Twark_Main on 11/30/2022 06:00 pm...polar caps... act as the (level-setting) "cold traps" on Mars.Of course not. CO2 freezes far from the caps. Quote"The temperature gets so low, you start freezing the atmosphere onto the surface," said Sylvain Piqueux of NASA's Jet Propulsion Laboratory... "Once you reach that temperature, you don't get colder, you just accumulate more frost. So even on the polar caps, the surface temperature isn't any colder than what these lower-latitude regions get to overnight."
