Lack of magnetic field on Mars

[Silvestru]

I was recently reading about Terra-forming Mars and possible colonization.

I saw that a big problem with this is that Mars does not have a magnetic field which makes dangerous radiation reach the surface.

Why do some planets have a magnetic field and some don't?

I found this theory as a reference but there are smaller planets than Mars that do have a magnetic field so it does not hold up.

http://www.astronomynotes.com/solarsys/s7.htm

[Sensei]

51 minutes ago, Silvestru said:

Why do some planets have a magnetic field and some don't?

Liquid (and moving) metal in the core is the most accepted theory of formation of external magnetic field around planets.

"Mars possibly hosted a core-generated magnetic field in the past.[18] The dynamo ceased within 0.5 billion years of the planet's formation.[2] Hf/W isotopes derived from the martian meteorite Zagami, indicate rapid accretion and core differentiation of Mars; i.e. under 10 million years.[13] Potassium-40 could have been a major source of heat powering the early Martian dynamo.[17]"

https://en.wikipedia.org/wiki/Planetary_core

 

Google for "liquid sodium magnetic field" for articles about experiments created in labs on Earth.

 

 

Liquid metallic core can't last forever. Planets are cooling down. Radioactive isotopes increasing temperature and keeping core liquid, are exhausting.

 

Edited September 13, 2017 by Sensei

[Silvestru]

Hmm I get that but Mars has a Liquid core. Does it have to do anything with it's rotation speed as well?

Update: I found some information regarding the Magnetic fields of our Solar system planets.

• Mercury has a magnetic field. It's not super strong (possibly because it rotates fairly slowly), but it does exist.

• Venus does not have a magnetic field. We're fairly sure the core is liquid metal, so for some time scientists believe it lacked a magnetic field because it rotated too slowly. It now seems to be the case that because its interior has such an even temperature throughout, there's little to no convection going on in the core.

• Earth has a magnetic field. In fact it's very strong for our size, possibly because we rotate at a decent rate, and there's a strong thermal gradient between the center and outer edge of the core.

• Mars does not have a magnetic field. It almost certainly did once - we still see crustal remnants of this ancient field in some rocks - but then its liquid metallic core cooled and solidified.

• Jupiter has a magnetic field. It's incredibly strong - much stronger than any other planet. This is probably because about ~70% of the radius is filled with liquid metallic hydrogen, and the planet rotates very quickly.

• Saturn has a magnetic field. Similar to Jupiter, Saturn's interior is filled with liquid metallic hydrogen (although not quite as much), and rotates quickly. Curiously, unlike any other planet in our solar system, its magnetic axis and rotation axis are almost perfectly aligned...we don't know why.

• Uranus has a magnetic field. This is a bit odd, since Uranus is not large enough to have the pressures required for metallic hydrogen. We currently believe this is because there is an "ionic ocean" beneath the atmosphere. Essentially this is a mix of water, ammonia, ammonia hydrosulfide, etc. Technically you do not need to have a rotating, liquid metal to generate a magnetic field - just a rotating, electrically conductive fluid.

• Neptune has a magnetic field. Similar to Uranus, most likely caused by a deep ionic ocean.

 

Now my mind is going to places like is there any way of reintroducing a magnetic field to a planet? Is it possible to increase a planets core temperature without sabotaging surface conditions? 

[mistermack]

I remember reading recently that the Sun has a magnetic field. Apparently it's been twice as strong as normal over the last 100 years.

Some Danish scientists are making the argument that the Sun's magnetic field deflects cosmic rays, so when it is strong, we get less of them. And the argument goes on that cosmic rays help to seed low level clouds, and low level clouds are strong reflectors of solar energy back into space.

So the recent global warming could be due to the currently strong solar magnetic field, (and hence less low-level cloud) and less due to CO2 levels.

I don't want to divert the discussion, I just thought it was an interesting addition. The Sun's magnetic field flips every 11 years, whereas the Earth's flips over millions of years. I have no idea what the mechanism is, but in the case of the Sun, it doesn't seem to make a lot of difference.

Edited September 13, 2017 by mistermack

[Silvestru]

43 minutes ago, mistermack said:

I remember reading recently that the Sun has a magnetic field. Apparently it's been twice as strong as normal over the last 100 years.

Some Danish scientists are making the argument that the Sun's magnetic field deflects cosmic rays, so when it is strong, we get less of them. And the argument goes on that cosmic rays help to seed low level clouds, and low level clouds are strong reflectors of solar energy back into space.

So the recent global warming could be due to the currently strong solar magnetic field, (and hence less low-level cloud) and less due to CO2 levels.

I don't want to divert the discussion, I just thought it was an interesting addition. The Sun's magnetic field flips every 11 years, whereas the Earth's flips over millions of years. I have no idea what the mechanism is, but in the case of the Sun, it doesn't seem to make a lot of difference.

You are not diverting at all. This is really interesting. I wish I had a more scientific understanding of such things because as you said , twice the magnetic field has not affected us significantly. I have to read more on this subject.

 

[petrushka.googol]

The Earth's magnetic field is produced by a system of huge whirlwinds of molten metal in the outer core known as a "geodynamo". These vortices arise from a combination of two factors: convection, and the Coriolis force. Convection currents act as the basic pathways that the molten metals take, while the Coriolis effect causes the molten metal to spin and form into defined column-like structures, oriented on the same axis as the Earth's rotation. This process is called Dynamo Theory.

In view of the above Mars has only a solid core that prevents the development of a global magnetosphere. (no differentiation into outer and inner core).

[swansont]

6 hours ago, petrushka.googol said:

The Earth's magnetic field is produced by a system of huge whirlwinds of molten metal in the outer core known as a "geodynamo". These vortices arise from a combination of two factors: convection, and the Coriolis force. Convection currents act as the basic pathways that the molten metals take, while the Coriolis effect causes the molten metal to spin and form into defined column-like structures, oriented on the same axis as the Earth's rotation. This process is called Dynamo Theory.

In view of the above Mars has only a solid core that prevents the development of a global magnetosphere. (no differentiation into outer and inner core).

!

Moderator Note

You should cite your sources when copy/pasting. Failure to do so is plagiarism.

(lifted from here)