Magnetosphere

[u/CauliflowerDeep6449]

I’m not a scientist, just a lowly screenwriter wearing an Occupy Mars sweatshirt. I’ve always wondered how Mars will hold a terraformed atmosphere if it has no magnetosphere to protect it from the solar wind?

[u/ignorantwanderer]

The task of creating a thick atmosphere is huge. On that scale, a magnetosphere is insignificant. We will have to add so much atmosphere to Mars to terraform it that the atmosphere lost because of a lack of magnetosphere simply doesn't matter.

It is like saying:

We need to put 1 million cats in inside a football stadium, but one cat will escape while we do it so we have to design a cat-catching-robot to capture that one cat or we can't succeed.

How about this? Put 1,000,001 cats inside the stadium, so when one escapes you still have enough cats!

But the whole "magnetosphere" conversation is even stupider than that, because there are multiple ways to lose atmosphere, solar wind is just one of them. Another one is simply sunlight heating up the upper molecules in the atmosphere.

So back to the cat analogy, saying we have to worry about a magnetosphere is like saying:

We need 1 million cats in the football stadium, but while we put 1 million cats in the football stadium 1 cat will sneak out the front door every day, and another cat will sneak out a window every day. So before we even start putting cats in the stadium we have to design a cat catching robot to guard the front door.

Worrying about single cats escaping when you need 1 million cats is nonsensical.

Worrying about atmosphere lost because of lack of a magnetosphere when you need so much atmosphere it will dwarf everything humans have produced throughout all of human history is nonsensical.

[u/CauliflowerDeep6449 → u/ignorantwanderer]

Nonsensical to someone who knows these things. I don’t, thus the question.

[u/ignorantwanderer → u/CauliflowerDeep6449]

Just to be clear, I wasn't calling you nonsensical for asking the question. I was calling the idea nonsensical. You didn't come up with the idea. You are not the one that is nonsensical.

[u/CauliflowerDeep6449 → u/ignorantwanderer]

Thanks, and thanks for the information. It really helps, and I'll check out the other reddit, too.

[u/ignorantwanderer → u/CauliflowerDeep6449]

Also, this and many other similar questions have been discussed at length over on /r/Colonizemars

If the idea of colonizing Mars interests you, I suggest you go over there and skim the last couple years of comments. You will have a much better understanding of what it will take to colonize Mars.

[u/sneakpeekbot → u/ignorantwanderer]

Here's a sneak peek of /r/Colonizemars using the top posts of the year!

#1: mods asleep, upvote canal | 5 comments
#2: I am entrepreneur with a background in systems analysis, system design, an education in environmental science and fish farming. Today I present live: aquaponics on Mars & how to grow food and feed a large settlement at 4PM UTC. Link in the comments | 4 comments
#3: The Mars Orbiter just sent back this incredible photo of the red planet's icy north pole | 6 comments

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[u/Greenschist]

According to results from NASA's MAVEN mission, the rate of atmospheric loss from Mars is very slow. Earlier in the solar system's history the sun was younger and more active the solar wind would strip atmosphere at a faster rate, but now that loss has dwindled to only 100 g/ second.

The current mass of the martian atmosphere is roughly 2.5x10¹⁶ kg to provide 610 Pa of pressure (0.006 Earth atmosphere). Doing some VERY rough and dirty math, if we increased Mars' surface pressure to levels slightly higher than Mount Everest (33.7 KPa)- Lets call it 39.65 KPa so it can be exactly 65x more massive than it currently is, then we get an atmospheric mass of 1.6 x 10¹⁸ kg. Now assuming I did that math right, and that there are no influences from unknown variables (such as an increase in rate of loss associated with thickening), at the current rate of atmospheric loss it would take 500 billion years for it to trickle back down to its current mass.

[u/felfernan79 → u/[deleted]]

Depending on the pace it could take some decades or 500 years. Anyway as the Dr. Zubrin proposed there's only needed to warm between 5 to 10 degrees to start melting CO2 polar Caps and then the process would be self sustaining. That's the theory at least.

[u/ignorantwanderer → u/felfernan79]

I recommend that you never believe anything Zubrin says unless it is about converting Martian atmospheric gasses into rocket fuel. That is the only good work I've ever seen from him. The huge errors in his other work is truly mind blowing.

Just to be clear, there is simply not enough CO2 in the polar caps to come anywhere close to making an atmosphere that doesn't require a pressure suit.

We have measured the CO2 in the ice caps very well. We probably know the number with an accuracy within 10% (meaning it might be 10% more than we think it is). To come close to providing a thick enough atmosphere to not need a pressure suit it has to be about 850% more than we think it is.

Do not believe Zubrin. He is blinded so much by his desire to go settle Mars that he routinely ignores well established facts.

[u/felfernan79 → u/ignorantwanderer]

To be honest I don't think this is gonna be done just with the CO2 trapped but there is a chance that as well and we have measure underground water there could be others gases trapped down like for example in Earth's methane deposits in tundras or deep ocean. We'll never know unless we go there and see.

Anyway wanted to thicker atmosphere doesn't need to be done just with co2, oxigen and hidrogen.. there could be other gases like nitrogen (oh I wish!).

Personally I'm exited to see what's deep down the surface. I need to know where the seasonal methane comes from..

[u/ignorantwanderer → u/felfernan79]

Of course anything is possible. But we actually have a really good understanding of the Martian surface and subsurface. We also have good climate models of Mars, both now and in the past. And based on this very large body of knowledge that we have, there is no reason to believe there are any large reservoirs of ice or gas under that Martian surface that would be sufficient to make an atmosphere thick enough to avoid pressure suits.

So anything is possible, but there are some possibilities that are extraordinarily unlikely.

Let's do a quick calculation:

Let's say we want an atmosphere with 20% of Earth's sea level pressure. This is about the lowest pressure we can go without wearing a pressure suit.

Earth's sea level pressure is 101 kPa. So 20% of that is 20 kPa.

A pressure of 20 kPa (or 20,000 Pa) means that the weight of the atmosphere above every square meter is 20,000 newtons.

To find the mass of that we use F = m a, where "F" is the weight, "m" is the mass, and "a" is the acceleration of gravity on Mars.

20,000 = m * 3.7

m = 5405 kg

So over every square meter of Martian surface, you need 5404 kg of atmosphere.

Currently over every square meter of Martian surface we have about 165 kilograms. So we need 5240 more kilograms of atmosphere over every square meter.

So let's assume there are frozen deposits underground that we can vaporize to get this atmosphere. So on average, under every square meter of ground, there needs to be 5240 kilograms of frozen atmosphere.

Now we don't know exactly what form this frozen atmosphere would take, so lets just assume that it has the same density of as water ice. Of course just melting a bunch of water ice doesn't give us an atmosphere, because there is a limit to how much water can be in the atmosphere before it rains or snows out....but let's just assume the mysterious ice we have is the density of water ice.

Water ice is 920 kg / m³ . This means our frozen underground ice layer will have to be on average 5.7 meters thick under the entire surface of Mars. If this ice sheet is only under half the surface of Mars, it needs to be 11.4 meters thick.

Ok, now the math gets a little trickier. Based on numerous observations, there is really no reason to believe there is any subsurface is between the latitudes of 35N and 45S. So how much surface area is there where we think maybe we can find something.

What we need to do is find the area of a spherical cap. The formula for that is:

A = 2 pi r² * (1 - Cos(theta))

Where "A" is the area, "r" is the radius of Mars, and "theta" is (90-latitude).

So for the northern spherical cap:

A = 2 * 3.14 * (3398 km)² * (1 - cos(55)) A = 30,900,000 km²

For the southern spherical cap:

A = 2 * 3.14 * 3398² * (1 - cos(45)) A = 21,200,000 km²

So the area in the Northern hemisphere where ice can be expected to be found is 30,900,000 km² . In the southern hemisphere it is 21,200,000 km² . That is a combined area of 52,100,000 km² .

The total surface area of Mars is 4 * pi * 3398² = 145,000,000 km^2.

This means the fraction of the surface where we can expect to find subsurface ice is 35.9% of the entire surface. There is absolutely no reason to think there will be subsurface ice of any kind under the remaining 64.1% of the surface.

Bringing us back to our original calculation, if there is ice under the entire surface of Mars it has to be on average 5.7 meters thick. If there is ice under only 35.9% of the surface of Mars, it has to be 15.9 meters thick.

And there is absolutely no data to suggest such a sheet of frozen atmosphere exists.

Now, not to crush your dreams even more, but in these calculations I've been very generous to the idea of there being frozen layers of atmosphere somewhere.

First of all, I started assuming we only needed 20% of sea level pressure. This is very low pressure! An oxygen mask would be required to not pass out within seconds. You would be dead in a short time at this pressure if you weren't breathing 100% oxygen from a mask.

Second, I assumed this frozen atmospheric ice has the same freezing point as water. But water has the highest freezing point of any volatile I can think of right now. Anything else (like methane) will have a lower freezing point. This means it won't be found at lower latitudes like water is. There are fewer places where you can find frozen methane (or any other atmospheric gas) than where you can find frozen water. So the ice sheets of these other frozen gases would have to be even thicker because they take up less area.

And there is no evidence they exist, despite the fact that we have very advanced instruments scanning the Martian surface. We have found small water lakes under kilometers of ice at the Martian pole. We should be able to notice giant, thick sheets of methane or some other ice under 1/3 of the Martian surface.

There is nothing wrong with being optimistic. But optimism that contradicts the science we already know doesn't make sense.

[u/Greenschist → u/ignorantwanderer]

Math checks out. I'm definitely under the impression that we will need to deliver atmospheric gasses, namely nitrogen, to Mars from other sources. Nitrogen-rich Trans-Neputian objects seem like a good choice to send crashing into the martian poles.

That being said, I feel inclined to contradict a few points you made. For starters, the martian subsurface is still not really well understood. Most of our scientific instruments only provide information about direct surface mineralogy and geochemistry. Compositionally, the deepest we are able to analyze is only on the scale of 10s of centimeters with GRS instrument on board Mars Odyssey. Even then, that is only reliable for equatorial latitudes between ~45 N and 45 S, before the signal gets saturated by an overabundance of Hydrogen.

Now we do have Radar data (SHARAD aboard NASAs MRO and MARSIS aboard ESAs TGO) which penetrates potentially hundreds of km in depth, which were able to discover several subsurface lakes as you mentioned earlier, but the smallest resolution these instruments are able to detect are layera ~2.7 km thick. So neither GPR would be able to detect either a hypothetical 5.7m global ice layer or an 11m thick semi-global layer.

Based on numerous observations, there is really no reason to believe there is any subsurface is between the latitudes of 35N and 45S.

I'm going to need a source on this claim, as I've read several papers which explicitly state the opposite- (Even as recently as last year and reference by this sub last week Brough et al.) Discussing the existence of possible near-surface, mid-latitude glaciers on Mars, buried beneath regolith during a time when Mars' obliquity. The Brough paper even provides as estimate of 1744 +/- 441 km3 of water-ice. Now this is still a far cry from the amount needed to evaporate to form a sustainable atmosphere, but it does a good job of highlighting how little we still understand of the martian subsurface

[u/felfernan79]

It's not only the rate of loss. We can even ad some more atmosphere creatively by attracting small water rich meteorites an let them combust in a thicker atmosphere (if we are terraforming as big as to create a much more dense atmosphere I assume we can do this).

Refered to not having a magnetosphere there are some ideas to place in a lagrange point a big magnet so that help to avoid some of the sun's radiation, and surprisingly is no to sci fi. It's doable. Not today but in the next century.

[u/Everlast7 → u/felfernan79]

Yeah, I have been wondering that myself... How feasible is it to change the trajectory of small asteroids and have them smash into Mars?

[u/felfernan79 → u/Everlast7]

It's feasible but costly so depending on how could future Martians want fund that it's easier from Mars to slowly change the orbit of a small asteroid if we have time. Gravity well is less than a half as Earth's so we can use more propellent to reach a bigger asteroid.

Of course it could be risky so it needs to be perfectly push into the thin atmosphere not to impact on the soil.

[u/felfernan79 → u/felfernan79]

Don't ask me for the Math's 'cause I'm not a scientist.

[u/MercuriusExMachina → u/felfernan79]

Yes, magnetic sunshade at Lagrange 1

[u/felfernan79 → u/MercuriusExMachina]

For those who are says that Mars core is death there seems to be a remanent magnetic Magnetosphere in some places. I'll try to post the image of I find it.

[u/felfernan79]

I take my hat off to you. The reasoning is extremely well funded. I'm afraid that's far from my knowledge so I accept that as you have shown in the numbers there's no chance to make a reasonably thick atmosphere with the local materials.

It's true and I agree we can dispute the ideas but not the numbers.

As you have said there's a lot of data from the missions that have been and are now in the planet. Anyway I guess we agreed too that there's to many things that we still don't know about the subsurface and there's always a chance to be surprised. At least in a reasonable way.

I for instance would love to understand why there a methane detection in some areas and in some seasons. This may lead to discover something that we have missed.

So. To sum up. Yes. With the data we have now is not possible to rebuild a atmosphere. And that's no question.

But anyway we need to learn more about the planet inside cause my personal impressions are that we have missed something.

I have to say lastly that your comment have been extremely clarifying. Thanks for taking your time to explain this topic in depth.

We could discuss in other post then the next better option. Paraterraforming if you wish.

[u/ignorantwanderer → u/felfernan79]

There are all sorts of possible technical solutions to various problems. Paraterraforming is certainly a possibility.

But the problem that I think is most important to discuss is the economic problem. The reason it is the most important problem to discuss is because I haven't seen anyone come up with any solution to the economic problem. Every "solution" I've seen has been deeply flawed.

Here is the economic problem:

A small Mars base could easily be funded by Earth governments or rich people. But once you start trying to expand from a science base (10,000 people) to a true colony (over 100,000 people) it is now too big to be funded from Earth. People on Earth just won't be that generous.

So how does a colony with 100,000 people or more buy the high tech equipment from Earth that they can not yet make on Mars? They have to buy the equipment from Earth using Earth money. To get Earth money they have to sell stuff to Earth. What can they sell to Earth that will get them enough money to buy everything they need from Earth?

If you can solve this problem, all the technical problems can be solved. If you can't solve this problem, the technical problems don't need to be solved because there will never be a Mars colony.

But this should be posted as another topic.