by Chris Peterson » Sat Apr 17, 2010 1:03 am
makc wrote:1st, they say Earth axis is stable only because we have our moon, and Mars axis change direction like crazy, hence it doesnt have stable climate. Is it really so? Does Mars have huge precession?
Yes, that is basically true, but it isn't a matter of precession. What the Moon does is stabilize the range of angles that the Earth's axis can be at (the obliquity of the equinox). For the Earth this is about 23.5°, and only varies about a degree either way. The axial tilt of Mars is currently about 25°, very close to that of the Earth. But without a stabilizing moon, the tilt of Mars changes by about 40° over millions of years. That certainly has major climatic consequences, although it isn't really correct to say that the Earth has a stable climate over millions of years, either. In fact, Earth's climate is probably much less stable than that of Mars, simply because it is so much more complex.
2nd, they say we don't go to Mars because solar radiation is so very high beyond Earth magnetic field. How can that be a problem? I mean here on Earth the only way to feel its magnetic field is to look at compass needle, and some minor quantities of iron ore (not to mention neodymium) can totally mess it up. How come solar radiation is so strong that we can't protect would-be interplanetary spaceship, yet weak Earth field deflects it?
The Earth's magnetic field is actually pretty strong. Strong enough to deflect most charged particles coming from the Sun. Mars does not have a strong magnetic field, so those particles can reach the ground. Ionizing radiation like that is not a good thing for the human body.
[quote="makc"]1st, they say Earth axis is stable only because we have our moon, and Mars axis change direction like crazy, hence it doesnt have stable climate. Is it really so? Does Mars have huge precession?[/quote]
Yes, that is basically true, but it isn't a matter of precession. What the Moon does is stabilize the range of angles that the Earth's axis can be at (the obliquity of the equinox). For the Earth this is about 23.5°, and only varies about a degree either way. The axial tilt of Mars is currently about 25°, very close to that of the Earth. But without a stabilizing moon, the tilt of Mars changes by about 40° over millions of years. That certainly has major climatic consequences, although it isn't really correct to say that the Earth has a stable climate over millions of years, either. In fact, Earth's climate is probably much less stable than that of Mars, simply because it is so much more complex.
[quote]2nd, they say we don't go to Mars because solar radiation is so very high beyond Earth magnetic field. How can that be a problem? I mean here on Earth the only way to feel its magnetic field is to look at compass needle, and some minor quantities of iron ore (not to mention neodymium) can totally mess it up. How come solar radiation is so strong that we can't protect would-be interplanetary spaceship, yet weak Earth field deflects it?[/quote]
The Earth's magnetic field is actually pretty strong. Strong enough to deflect most charged particles coming from the Sun. Mars does not have a strong magnetic field, so those particles can reach the ground. Ionizing radiation like that is not a good thing for the human body.