Do any planets in our solar system besides Earth have magnetic fields?
Question:
Answer:
They all have magnetic fields but some are stronger than others.
Magnetic Field
The first indication of the weakness of the magnetic field of Mars was obtained during the Mariner 4 spacecraft flyby in 1965. At a closest approach of 3.9 Mars radii, no indication of the Earth-like dipole magnetic field predicted by scaling arguments from theory was detected. Still, a shock-like disturbance in the solar wind signaled the presence of an obstacle approximately the size of Mars. Most subsequent magnetic field measurements in the vicinity of Mars were carried out on a series of five MARS spacecraft launched by the Soviet Union between 1971 and 1974 (see Soviet MARS missions). Several of these successfully operated in orbit for periods long enough to both confirm the Mariner 4 results and to measure the disturbance of the interplanetary magnetic field caused by the obstacle. However, none of these spacecraft approached Mars closer than ~ 1300 km or ~ 1.3 Mars radii from the center of the planet, and none probed the solar wind wake inside of the optical shadow, where the magnetotail of an intrinsic magnetosphere resembling a weak version of Earth's would be found. The Viking landers reached the surface of Mars in 1976, but did not carry magnetic field experiments its part of their scientific payloads. although they made ionospheric measurements of relevance to the magnetic field question. Because the available measurements could be interpreted front the viewpoint of either a small Earth-like magnetosphere, or a Venus-like ionospheric obstacle, different researchers have adopted both of these paradigms for over a decade. Their divergent views depended on the techniques and arguments used in analyzing the still ambiguous data (Luhmann and Brace, 1991).
These differences in opinion have to some extent been altered by the most recent magnetic field measurements on the Soviet Phobos-2 spacecraft in 1989 (e.g. Nature. 341. 19 October 1989, describes the first results). The orbit of Phobos 2 went into the deep wake of Mars, for the first time providing magnetic field data in the optical shadow at distances as close as ~ 2.7 Mars radii and as distant as ~ 20 Mars radii. These data unambiguously showed that the magnetic fields in the wake of Mars are determined by the interplanetary field orientation, and are thus not Earth- like, at least in the near-equatorial spacecraft orbit plane. The current upper limit on the dipole moment remains at ~ 10-4 times that of Earth, a value established on the basis of the previous observations. This moment is derived not from the wake data but from estimates of the subsolar altitude of the Martian obstacle to the solar wind of ~ 400 km. Additional indirect information concerning the magnetic field of Mars derived front ionospheric observations and the understanding of solar wind interactions is described below.
Today, the only other 'direct' information that Martian magnetism is from a special class of meteorites known as the SNC meteorites (q.v.) which are thought to come from Mars. Magnetic field analyses of these possible samples of the Martian crust indicate that magnetic fields of ~ 1000 nT may have been present on the surface of Mars at the time that these meteorites were ejected by a giant impact some 180 million years ago. (For comparison, the present field on Earth near the equator is about 3 X 104 nT. The present upper limit on the dipole moment implies surface fields of only a few tens Of nanotesla.)
The dynamo theory of planetary magnetism indicates that Mars may have had a dipole moment of about one-tenth of Earth's when it was first formed (Schubert and Spohn, 1990). The rotation rate Of Mars is approximately that of Earth and is thus sufficient for the operation of this initial dynamo. The other necessary ingredient of a convection driver in the core was supplied by heat left over from the accretion of the planet, which may have been effective for up to a few billion years. If such a field did indeed exist, evidence of it may still be present on the surface in the form of magnetized rocks and crustal regions like those observed on the Moon. No observations indicating the presence of such fields have been reported other than the aforementioned SNC meteorites' magnetization.
They all have electro-magnetic fields. Mars has a stronger one on account of its aptmosphere. This is not essential to life in my opinion, but since all planets have them there is no proof of that.
I do believe they have gravitational effects, but i haven't heard of magnetic field due to some lack of atmospheres on some planets.
Jupiter has a very strong one. You can listen to it (see link below).
Mars's magnetic field is very, very weak. This will be a problem for people on Mars, as the lack of a magnetic field allows them to be exposed to the intense radiation from the sun and space.
The presence or absence of an atmosphere has nothing to do with a planet's magnetic field.
Magnetic fields, simply put, are the areas of influence of a magnet. A magnetic field covers the whole area in which the attraction or repulsion of a magnet can be felt. For an everyday example: most kids know that if someone in their family is making dinner in the kitchen, they will get called in to help if they watch TV nearby in the living room, but not if they are in their bedroom upstairs (if they are lucky). So the chef's "magnetic field," as it were, extends to the living room, but not to the second floor of the house.
That is a magnetic field, but it is important to get the idea of a magnet straight. Everyone has seen and played with magnets; maybe you have sprinkled iron filings near one in a science class or played with the magnetic marbles you can link together as a string. It is not just iron bar magnets that show magnetism, though: the whole idea of magnetism is that in everything (a piece of iron or the graphite in a pencil), a tiny current is caused by electrons whirring around their nuclei. Two currents traveling in the same direction attract; two traveling in opposite directions repel. In a bar magnet like one you might have played with, the tiny atom-magnets are all lined up in the same direction, causing the "magnetic" property due to the attraction of like currents and forming north and south poles due to the lining-up.
Back to magnetic fields -- first of all, they are no haphazard things. Magnetic fields, though they can get pushed around (as we'll see later), keep their currents, and thereby their magnetism, in set places called magnetic field lines, running out of the south pole of the magnet and into the north pole. Since the currents are electrons and charged particles stay along magnetic field lines and do not jump around, this works out pretty well for the lines. This, to extend an analogy, is as if the chef in your house would only be able to say, "Please set the table, dear," if you were standing either two, or five, or fifteen feet away from him or her. The whole idea of magnetic field lines seems rather abstract, but you can prove it to yourself if you put a bar magnet under a sheet of paper and sprinkle iron filings on the paper. The filings will not only be attracted to the magnet, but will form circles of magnetic field lines around it. (See the picture if you do not have a magnet handy.)
Not your ordinary magnet
Whether you have heard it or not, take it for granted: the Earth is a sort of really big magnet. Just like a bar magnet, the Earth has a magnetic north and south pole and huge connecting magnetic field lines that form what scientists call the magnetosphere. This fact is what makes compasses work -- the north end of a compass repels magnetic north, so they point the same way.
However, do not get the idea that the Earth actually has some huge piece of iron like you might buy at a science store imbedded in it that makes compasses spin around. The cause of Earth's magnetism is actually the Earth's internal dynamo, which is so hot that a typical iron magnet would lose its magnetism, anyway. In this super-hot core, electrically-conducting molten iron flows around through a magnetic field in a closed electric circuit. Because some of the fluid is moving in the magnetic field and some is not, and because a couple of other necessary conditions in the core are satisfied, an electric current starts up as per the laws of physics. As we learned before, the presence of electric currents starts up magnetism. When slow changes in the flow of molten iron in the core occur, the Earth's magnetic field varies.
The magnetosphere is very important to everyone on the planet because it keeps most solar wind that could hurt power and satellites away from the Earth; charged particles coming out of the Sun have to follow the rules and can not jump from one field line to the next to get down to Earth.
We are not alone (at least as magnetospheres go)
As magnetospheres go, though, the Earth is not anything too special. Mercury, Jupiter, Saturn, Uranus, and Neptune all have magnetospheres, and all but Mercury's dwarf ours. Our sister planets, Mars and Venus, are the oddballs: space probes have found no evidence of structured magnetic field lines on either planet, only traces. Since magnets lose their magnetism when heated a lot, it makes sense that Venus, where it is hot enough to melt lead, does not have a magnetosphere. Therefore, it is Mars that is the real mystery: it is pretty cold and is quite like Earth in many ways . . . so why no magnetosphere?
Now, the point of the Mars Global Surveyor's magnetometer comes clear. As you are reading this, MGS is orbiting Mars and mapping out the planet's magnetism (or lack thereof) with its magnetometer. Every once in a while, anomalies are found, where some magnetized substance is buried beneath the surface. These anomalies were thought to have come up from a once-magnetized core and kept their magnetism when the planet lost its overall magnetism. Scientists working with the MGS hope that by mapping these anomalies they can learn about the extinct magnetic core or dynamo within Mars and about Mars' surface evolution.
Magnetic fields surrounding planets are caused by the motion of electrically charged particles inside the planets. This motion occurs in rotating planets with molten, conductive interiors, where currents of charged particles flowing inside the planets can generate large magnetic fields. Of the terrestrial planets, only Earth has both the fluid core and high rate of rotation required to create a strong magnetic field. Venus has a fluid core, but it rotates too slowly—nearly 273 days per rotation—to generate a large field. The moon, Mars, and Mercury appear to lack the required fluid core. Earth’s magnetic field is one of the surest indicators that it has a fluid interior.
Mercury has a magnetic field that is about 1 percent as strong as Earth's. The presence of the field and its global extent together suggest that the core of the planet is largely liquid iron, which produces a magnetic field as it moves. Scientists believe Mercury's crust insulates the planet's outer core, keeping it liquid despite the very cold temperatures on the dark side of the planet.
Neptune, like Earth, is surrounded by a magnetic field, a region of space that exerts a small force on electrically charged or magnetic material. Scientists believe that the slow escape of heat from the planet’s core circulates currents of electrically charged particles in Neptune’s deep ocean, generating a magnetic field. Neptune’s magnetic axis, the line indicating the direction of the force the planet’s magnetic field exerts, is aligned at an angle of 47° to Neptune’s axis of rotation. The influence of Neptune’s magnetic field extends for several hundred thousand kilometers above the planet.
Uranus, like Earth, is surrounded by a magnetic field, a region of space that exerts a small force on electrically charged or magnetic material. Uranus’s deep oceans contain electrically charged particles called ions. Ocean currents on Uranus make these charged particles move through the ocean, which in turn creates a magnetic field. Scientists believe that ocean currents in the other Jovian planets—Neptune, Saturn, and Jupiter—are created by heat released from the planets’ cores. The core of Uranus releases less heat than the other three Jovian planets, however, and astronomers are unsure about what causes ocean currents in Uranus’s fluid interior. Uranus’s magnetic field is similar in strength to Earth’s magnetic field. Uranus’s magnetic axis (the line joining the north and south poles of its magnetic field) is aligned with the planet’s strongly tilted rotational axis, although the magnetic field is offset from the planet’s center. The influence of Uranus’s magnetic field extends for several hundred thousand kilometers above the planet.
Yes, other planets do.
All four giant planets--Jupiter, Saturn, Uranus and Neptune--were visited by Voyager 2. (The first two were also visited by Pioneer 10 and 11 and by Voyager 1, and the probe Ulysses flew by Jupiter, while the probe Galileo is currently in orbit around it.) All four have magnetic fields much stronger than the Earth's, in the sense defined above for Jupiter. Saturn's magnetic axis, remarkably, seems to be exactly lined up with its rotation axis, within the accuracy of observations.
The magnetic axes of Uranus and Neptune, on the other hand, are inclined by about 60° to their rotation axes. The shape and properties of a planetary magnetosphere depends on the angle between the flow of the solar wind (i.e. the direction from the Sun) and the magnetic axis, and for those two planets, that angle is rapidly changing all the time. As a result, their magnetospheres undergo wild variations during each rotation, although both manage to contain trapped particles. The origin of all those field is unknown: Saturn is big enough to produce metallic hydrogen in its core, but Uranus and Neptune are not.
The planet Venus was visited by Mariner 10 in 1974, which continued from there to Mercury. Venus was found to be unmagnetized: the solar wind is only stopped by its upper atmosphere, the ionosphere, creating a completely different type of magnetosphere, more like a comet's tail. On the other hand, tiny Mercury--an airless rock only moderately bigger than our Moon, rotating very slowly--surprised observers by being magnetized. Its magnetic field is weak and probably does not extend far enough to trap many particles, but as the spacecraft passed through its nightside tail, it observed a sudden spasm in which particles were apparently energized. To learn more about all this, NASA has scheduled the "Messenger" mission to fly to Mercury and orbit it.
Mars and the Moon have permanently magnetized patches of rock on their surfaces, suggesting that even if they now lack a dynamo field, at some time in the past they possessed one. That would agree with the giant volcanoes (apparently extinct) observed on Mars, which suggest a hot interior.
The magnetized patches on that planet, first observed by the Mars Global Surveyor, are particularly intriguing because they seem to form strips, reminding researchers of the magnetized strips observed on the sea bottom on Earth, from which the idea of plate tectonics emerged. Magnetic observations on Mars, however, are not yet detailed enough to allow any firm conclusions to be drawn.
Planetary magnetic fields thus seem to be the rule, not the exception, at least in our solar system. About a thousand years have passed since the discovery of the magnetic compass gave the first hint of such fields. As their study enters its second millennium, it faces more unanswered questions than ever before.
Technically, all planets have a magnetic field, though it could be extremely weak. Mars magnetic filed is 1/1000 the strength of the one on Earth. On the other hand, Jupiter's magnetic field is 10 times stronger than Earth's.
As to your point of magnetic field being necessary for the development of life, we will not know for sure until we find enough life forms in the universe to get an appreciation of its importance, or until we now enough about life development to deduct that it is absolutely necessary.
But, if it can be said that the magnetic filed does protect the earth from some harsh radiations that can sterilize the planet, can a planet without the magnetic filed generated Van Allen belt that protect us support life if it orbits a star that does not put out as much radiation as our sun (a less active, smaller star)?
Magnetism is through out the universe, as well is gravity, but these don't create a single cell.
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