# How long for Life on Earth to disappear after the magnetic field is gone?

Evil Wizard got his hands on a Handwavium Wand, and wished the Earth's magnetic field no more.

Now the surface is vulnerable to solar wind, solar radiation and cosmic radiation.

How long will it be till life is gone on the planet (land) surface?

Bonus points if you state how long till the oceans are also void of life.

• To quote Dr. Ian Malcolm, "Life finds a way." – Nuclear Wang Sep 27 '16 at 18:39
• Earth's magnetic field vanishes every few 100k years, for quite some years, and that has never caused mass extiction, afaik. Lighter planets like Mars are supposed to loose their atmosphere if it is no longer protected by the magnetic field. The particle radiation somewhat increases the temperature in the upper layers. – Karl Sep 27 '16 at 19:51
• See this talk for details on the physics as occurred on Mars. With more depth of the mechanisms understood you can then apply to Earth. – JDługosz Sep 27 '16 at 23:18
• This question was asked on Earth Science.SE. The answer given there was "between billions and trillions of years", with some indication that newer research shows the magnetic field doesn't really reduce atmosphere loss, just changes where it's lost from. Not sure those are good enough answers to really say "your question was already answered elsewhere", especially since the accepted answer just says "it's complicated". – MichaelS Sep 28 '16 at 5:07

## Atmosphere Blowing Away

NASA estimate for Mars atmosphere stripping by solar wind:

http://www.nasa.gov/press-release/nasa-mission-reveals-speed-of-solar-wind-stripping-martian-atmosphere

Earth is closer to the sun than Mars, so assuming a inverse square relation the solar wind would be about 2.5x stronger at Earth, Also earth's atmosphere is denser (160x) making a better target, but Earth has a higher gravity (3x) so my estimate would be for Earth to lose ~5 kg/s of atmosphere or 432,000 kg a day.

Earth's atmosphere is 5.15×10^18 kg

So at that rate of depletion the atmosphere would be gone in ~33 million years.

Of course some of the oceans gases would also start to evaporate at lower pressure and as the atmosphere decreased the rate would decrease so it would actually likely be longer, but as far as planets go that's pretty soon.

The big danger here is that the solar wind would blow away the ozone layer, which block ~98% of the medium-frequency ultraviolet light emitted by the sun, but as above it would not be instantaneous, and the rest of the atmosphere would continue to filter some of the UV radiation.

https://en.wikipedia.org/wiki/Ozone_depletion#Consequences_of_ozone_layer_depletion

This would be bad, but unlikely a total extinction level event, greatly increased levels of skin cancers in humans and animals (easily +100x), and widespread biological damage with likely extinction of UV sensitive species (specifically bacteria). A lot of species have already evolved UV defense mechanisms, things like melanin, and actually actively use UV to produce vitamin D. With the increased UV levels life would adapt, humans may not survive the various collapses of ecologies, but life definitely would survive it.

• How can the density of the atmosphere have anything to do with the escape rate? – Karl Sep 27 '16 at 20:12
• @Karl pressure and probability of collision. Solar wind are actually supercharged particles. – Mindwin Sep 27 '16 at 20:13
• Nonsense. Every particle that hits the atmosphere collides with some molecule in it. The temperature in the upper part of the atmosphere, where the mean free path lenght of particles goes -> infinity, is the important point. – Karl Sep 27 '16 at 20:18

Never is the answer you are looking for. Animals and plants will go extinct after a while, but I would say much later than what Josh calculated. However, extremophiles will keep on living. Some of them do not need air and get the energy from the hot vents. They will survive for a very long while.

Also, humans would probably survive that event too. Building underground shelters, artificially creating habitats, using earth's heat as power source, we will grow plants underground using growing lights. Rooting out humanity is not that easy.

• Absolutely nothing will happen. Slighly increased genetic mutation rates will speed up evolution to some extent, and the whole biosphere will alter a bit to adapt to the higher radiation level. – Karl Sep 28 '16 at 20:00
• Earth will definitely start to loose atmosphere at an accelerated pace. The mechanics involves in radiation breaking apart water molecules and hydrogen escapes with the acceleration and the extra heat that the sun beams would provide. – Cem Kalyoncu Sep 28 '16 at 20:26
• The earths atmosphere above 20 km is essentially dry, because the upper troposphere is cold and still has enough pressure for water to condense and precipitate. – Karl Sep 28 '16 at 20:54
• The radiation will seep through to lower levels of atmosphere. After all, when the ozone layer disappears (which will, after magnetic field collapse), the only substance in the atmosphere that can effectively block the radiation will be water vapor. – Cem Kalyoncu Sep 29 '16 at 6:11
• Hydrogen atoms dissociated from water in the lower atmosphere don't escape to the ionosphere easily. The net loss will be marginal. OK, unless the temperature profile in our atmosphere is totally changed. I don't see that happening from the little extra power of solar particle radiadion. – Karl Sep 29 '16 at 7:40

The magnetic fields have effectively disappeared many times in the past (during periods of magnetic field reversal). This has not correlated with extinction events, so I see no reason to think it would be dangerous at all. https://en.wikipedia.org/wiki/Geomagnetic_reversal

Also, the current magnetic field funnels charged particles down onto the poles, yet the animals living at the poles seem unaffected.

• Magnetic field disappears during reversals for a relatively short amount of time. If it completely disappears, things would be different. – Cem Kalyoncu Sep 29 '16 at 6:13
• The magnetic field practically disappears for hundreds of years during a reversal of the magnetic poles, without any archeological effect except differently magnetised minerals. It simply is not an issue. – Karl Sep 29 '16 at 17:56