Aurors on Mars

www.universetoday.com/am/publish/mars_ex...aurorae.html?1722006

ESA Mars Express finds auroras on the Red Planet !!

Full story on link above.

Deirdre Kelleghan
www.irishastrosoc.org

Wow! I didn't think Mars had a thick enough atmosphere to help produce aurorae - even its magnetic field is quite weak!

Thanks for the link.
Very interesting.
So Mars doesn't have a planetary magnetic field but does have magnetic regions. Is this normal for the other planets in our solar system? Please excuse my lack of knowledge (was going to say ignorance but didn't like the look of it!).
So are gravity and atmosphere unrelated to the presense or absense of planetary magnetism, do we know or what are the best theories?
How does Mars have an atmosphere without planetary magnetism?

Don

So Mars doesn't have a planetary magnetic field but does have magnetic regions. Is this normal for the other planets in our solar system? Please excuse my lack of knowledge (was going to say ignorance but didn't like the look of it!).
So are gravity and atmosphere unrelated to the presense or absense of planetary magnetism, do we know or what are the best theories?
How does Mars have an atmosphere without planetary magnetism?

Some planets have magnetic fields some dont. And the processes responsible for them are very different. Earth has a rotating iron core, Mars did too probably - the magnetic flips are recorded in the magnetic zones; Jupiters massive magnetic field is caused by metallic hydrogen in the planet. Atmosphere and magnetic field are closley related; the magnetic field of a planet causes the solar wind to deflect around the planet and stops it ripping away the planets atmosphere. The atmosphere on Mars is very thin these days, perhaps it was a lot thicker in the past when the magnetic field was active. Gravity is needed to keep an atmosphere, and since gasses can fly away easily you need to be a sizeable (planet sized!) object; but to hold onto to an atmosphere in the presence of a solar wind requires a magnetic field. Venus being the exception since it doesnt appear to have a field and also has a thick atmosphere; one reason is that its atmosphere is thought to be replenished by outgassing or volcanic activity on the surface. When Venus Express reaches the planet we'll know more - orbital insertion in 48 days!

I wrote an essay on the subject a little while back. It's at www.cademuir.net/docs/planetaryBfields.php . It didnt score brilliantly mind you, but the article I'll do for arcturus will have taken my supervisors comments onboard and should be more readble!

Cheers,
~Albert

Jupiters massive magnetic field is caused by metallic hydrogen in the planet. At
~Albert

If you could "see" Jupiters magnetic field, it would appear as big as the full moon in the sky, its packs quite a wallop!

If you could "see" Jupiters magnetic field, it would appear as big as the full moon in the sky, its packs quite a wallop!

Oh yea!

Galileo, like Pioneer and Voyager before it, found a massive magnetic field. On the sunward side it extends to 2 million kilometres, while on the opposite side it extends to over a billion kilometres, out into Saturn’s orbit. This field creates a bow shock around the planet that extends for 30 million kilometres. The magnetic moment of Jupiter, the surface field strength at the equator times the cube of the radius, is 20,000 times that of the Earth.