Mars has gravity, as do all planets, but not a magnetic field.
The order of planets from the strongest magnetic field to the weakest is as follows: Jupiter, which has the strongest magnetic field of any planet in the solar system, followed by Saturn, which also has a significant magnetic field. Next is Uranus, with a weaker magnetic field than Saturn, and finally Neptune, which has the weakest magnetic field among the giant planets. Earth has a stronger magnetic field than both Uranus and Neptune but is weaker than those of Jupiter and Saturn.
Not all of the planets within our solar system have a magnetic field. Venus and Mars are the only ones that don't have a magnetic field (all other planets do have one).
No, Eris does not have a magnetic field. It is a dwarf planet located in the outer solar system and does not exhibit any magnetic field like some other planets do.
Planets are too far from each other to have any observable interaction of their magnetic fields.
Yes - several planets have magnetic fields that do not even vaguely resemble Earth's current field.
All planets have magnetic fields. I believe that in most cases, this magnetic field can act as a shield.
The planets within our solar system that have a magnetic field are: Earth, Jupiter, Mercury (though it is weak), Saturn, Neptune, and Uranus.
it affects the other planets and its rotation
Scientists believe Jupiter has a liquid metallic hydrogen core which allows it to form a strong magnetic field. Trapped magnetic particles form radio waves which are amplified by the planet's many moons and which are released into space.
The Earth's magnetic field is generated by a process called the dynamo effect, which is driven by the movement of molten iron and nickel in its outer core. Not all planets have the necessary conditions, such as a molten core and sufficient rotation, to generate a magnetic field.
Plants don't have a significant magnetic field. Perhaps you mean "planets"?