IF we launched a series of nuclear strikes on the polar ice caps on Mars, would it affect anyone in orbit around mars (assuming we could have them in orbit around Mars in such circumstances)?

  • $\begingroup$ Are you thinking of a particular scenario? I think the answer is it wouldn't matter, as anyone in orbit is far away and out of reach of radioactive particles created by the blasts, but I'd prefer to know more about what you are thinking. $\endgroup$ – kim holder Jan 26 '18 at 0:49
  • $\begingroup$ Short answer: It depends largely on these: 1) how big are the bombs 2) how far away are they from the explosions 3) how good are they protected by the wall of their spaceship (space station). But they answer is mainly: yes. The reason is that typical distances are far larger as the effective range of the radiation of the nuclear explosions, and they would have inherent defense from any non-radiative effect. $\endgroup$ – peterh Jan 26 '18 at 21:03
  • $\begingroup$ I am writing a short story dealing with the terraforming of Mars being delayed due to major dust storms. If nukes were dropped on the polar caps, I needed to know if it was reasonable safe for my characters to be in orbit. Thanks you for your help everybody. $\endgroup$ – Jimminy Critic Jan 27 '18 at 1:11

No, it wouldn't affect anything in orbit significantly. First of all, there won't be that many people in an orbit that is that high of inclination where it even passes over the poles. Secondly, it is too far of a distance to have any significant effects. Assuming a 1 Megaton bomb, there is $4.184\times10^{15}$ J of energy. The energy in an actual blast will be directed more along the horizon, but for simplicity let's use the worst case of equal direction in all direction. Let's even assume all of the energy that hits the ground will be reflected. The lowest orbit around Mars is about 300 km, anything lower then that and you will significantly change your orbit. The energy is then divided by the surface area of the half-sphere with that as a radius, or about 4000 J/m^2. That is the same amount of energy that a spacecraft receives from the sun over about 3 seconds in Earth orbit, which should be quite survivable. And that would be if the spacecraft was directly overhead. Of course, while a good chunk of that will be in the visible spectrum, higher energy portions could be more damaging.

The amount of the nuclear weapon's energy that is radiation is about 5%. According to Wikipedia, the survivable distance for a nuclear explosion due to the radiation effects is about 3 km from a 1 MTon bomb. Of course, much of that would be because the atmosphere of Earth will absorb the energy. The values there given are slant range, which means it is an absolute distance.

The other effect that could damage any satellite, not just including manned ones, is Electromagnetic Pulse. EMP is an interaction with a number of things, including the magnetic field of the Earth. The use of a thermonuclear weapon will further decrease it's effectiveness. It could affect satellites directly overhead, but probably would not break a satellite overhead. Here the thinner atmosphere of the planet actually helps, there will be fewer electrons being sent then a comparable burst on Earth.

Bottom line is, it isn't that likely that a manned spacecraft would be in an orbit that will pass over the poles, and even if it was, it wouldn't likely cause any real damage. The timing of the explosives should be such that no satellite is directly overhead, out of caution, but that shouldn't really affect anything.

  • $\begingroup$ Non essential side note: Getting the same energy in the form of gamma photons is much more harmful as in visible light, but it would be still far from doing any harmful. $\endgroup$ – peterh Jan 26 '18 at 21:05
  • $\begingroup$ True, but it wouldn't be all in gamma rays, only a portion of it. $\endgroup$ – PearsonArtPhoto Jan 26 '18 at 22:19
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    $\begingroup$ The majority of energy from a nuclear explosion is released as heat, not as ionizing radiation. I've included more information in this regard. $\endgroup$ – PearsonArtPhoto Jan 27 '18 at 22:34
  • $\begingroup$ Do you have any science-based source for the claim that the strength of the EMP field felt by a satellite would be lower for a lower atmospheric density? The prompt pulse caused by the Compton electrons will still happen, but at much higher altitudes because the low density of the Martian atmosphere will not strongly attenuate the gamma rays locally. No magnetic field is necessary for EMP effects to occur. It's a very different, and still complex scenario, and hand-waving is not really sufficient to determine if the size and shape of the EM transient will ultimately be larger or smaller. $\endgroup$ – uhoh Jan 28 '18 at 8:03
  • $\begingroup$ Also, the detonations would more likely be high in the atmosphere, not sub-surface. I think this answer still contains off-the-cuff assumptions not necessarily borne out by science. So I've asked Would the EMP from atmospheric polar nuclear detonations on Mars felt by orbiting spacecraft be larger or smaller than (if it were) on Earth? $\endgroup$ – uhoh Jan 28 '18 at 8:37

Yes, a nuclear detonation certainly might affect things in orbit!

Nuclear EMP could potentially be a serious issue for anything electronic which had line of sight to a nuclear detonation. That would include any GPS-like satellites, or those that provided comms links to Earth, as well as the electronics of the spacecraft that contained the people.

AFAIK on Earth, a detonation on, and especially under the surface would be much less of an issue to satellites than an atmospheric burst.

However this is Mars, and so the atmosphere at the surface is like the "upper atmosphere" of Earth, so I think anyone who's not particularly versed in the weaponization of nukes may not be able to definitively state how bad of an EMP would be caused by one, or even a series of ice-melting nukes.

21st century space-worthy electronics is likely to be more robust than 20th century stuff, but an EMP is not at all the same as a CME, so EMP protection would need to be implemented specifically, considering how sensitive all those deep-space receivers need to be.

edit: Since Mars' atmosphere is only roughly 1% that of Earth, the gamma-ray attenuation length is much larger, and so the characteristics of the resulting EMP from an atmospheric detonation will be very different than on Earth. So I've asked the follow-up question Would the EMP from atmospheric polar nuclear detonations on Mars felt by orbiting spacecraft be larger or smaller than (if it were) on Earth?.


Can people be in orbit around Mars and launch nukes at the poles? Theoretically it's possible.

Should this be done? No.

I'll assume the idea here is to use the nukes to release the water and carbon dioxide frozen the poles to start greenhouse-effect warming and thicken the atmosphere a bit. There are two problems with this approach: nukes aren't nearly as powerful as most people think they are, and you've just dispersed fallout over a large portion of Mars, concentrated in the areas where your most valuable resource (water) is.

Using a 1-Megaton bomb as a reference nuclear warhead, and the information on Wikipedia, the thermal effects would have a area of around 700-1200 sq km or so. By comparison, the rough area of the northern polar ice cap is 900000 sq km. You'll need about 1000 warheads to cover just the northern ice cap.

Now, you've irradiated the planet and melted some, but not all of the ice cap (it's kilometers-thick in places). And you've also caused a nuclear winter -- a lot of dust will be kicked into the atmosphere from detonating 1000 nukes.

The water will quickly refreeze and precipitate out of the air (not even accounting for the nuclear winter), but the fallout does not. So no surface operations are possible, the water supply is contaminated, and its now colder than when you started.

Bad idea all around.

  • $\begingroup$ This answer gives me an interesting choice: trust back-of-the-envelope math that uses blatantly wrong assumptions (nuke energy falloff with distance is due almost as much to atmospheric absorption, which is of course far less on Mars, as to sheer distance, for one, and no one has proposed melting the caps for the water, for two), or trust the math in one or more published books and research papers that I have not read. I'm going to take the difficult choice of the latter. $\endgroup$ – Nathan Tuggy Jan 26 '18 at 2:15
  • $\begingroup$ I disagree about nuclear winter. The bombs will kick up very little dust because they're detonating over ice. $\endgroup$ – Loren Pechtel Jan 26 '18 at 5:25
  • $\begingroup$ There was a q a while back about a proposal to use nukes to spread dark colored soil/dust over the caps and let insolation do the rest, but there were glaring problems with the proposal as written. $\endgroup$ – Russell Borogove Jan 26 '18 at 5:58
  • $\begingroup$ Yes, the energy falloff distance is related to atmospheric absorption, so your blast radius will be larger, but you lose significant heat transfer too. Also, it's not pure ice -- there is significant dust and soil mixed in. $\endgroup$ – Joseph Ennis Jan 26 '18 at 6:06

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