SATURDAY MARCH 17, 2012
Pic: the Milky Way
The human mind is lazy and wants easy answers. We don't look for things further than we have to, and we want explanations to be easy and quick. It's easy to imagine from what we hear on the TV and radio news each day from meteorologists and climatologists, that weather on earth is created and monitored constantly by the air, by temperature differences that come off the ground, by winds created at ocean surfaces and from gases released by cities and farms. This "surface" thinking is what also drives earthquake research. Geologists think that fault lines create earthquakes, that they are not just old scar-lines on hillsides, and so they study them. Also they think, because they have placed detection instruments there, that it has something to do with these things called tectonic plates, which are the parts of the crust of land that squats on top of the rest.
The thought doesn't often occur that perhaps the weather is there first and impacts on the rest, e.g the air, and that earthquakes come through from the deep and create faultlines and tectonic plate movement on their way to the surface. Just as the tide and sea surface are pulled either directly by the moon or pushed around by the land beneath them that are also pulled by the moon, and the air that rests on the water surface is pulled in the sea's direction by the surface water to create surface winds, so the land is pulled by massive forces acting on it from afar. And just as land surface temperature differences arise from adjacent oceanic temperatures, so, too, may pressures on the bulk of land that makes up our planet come from potential differences in magnetic stress that may arise in the "sea" of space that surrounds us. For we live in space, and the space we find ourselves in itself has a tide.
If it could be demonstrated that weather preceded atmosphere, then the whole of meteorology might be turned on its head. No more would forecasters worry about temperatures, pressures and wind speeds, because by the time these were measured they might realise weather had already happened. Thus far they have not noticed that if a gas is released from a chimney or a cow it gets dealt-to immediately by the weather that arrived beforehand and is now about. The tail arrives after the dog. The tail does not bring the dog. In the same way the seismologists arrive at a location after the quake has happened, and never before. They are all very learned after the fact, and nod their heads wisely. Yes, we predicted something would happen sometime, they say, and now you can see how right we were.
Weather simply cannot arise from air because there is weather on other planets, yet no air. Other planets have weather like earth, there are storms, hurricanes, possibly ice or snow. It is the same with earthquakes. Weather is a form of tidal disturbance that is caused, like our sea tides, by outside forces and transmits itself through whatever atmosphere a planet has. Most of the planets as well as a few smaller bodies in our solar system do possess an atmosphere. While weather conditions on earth may seem violent and extreme at times, even the worst weather on earth is nothing compared to an average day on most other worlds. Temperature extremes on earth can vary from a peak of 58°C measured in Death Valley, California, in the summer to as low as -90°C in Antarctica. Wind speeds at the surface are generally low but can reach nearly 320 m/h (200 mph) in hurricanes or cyclones in the worst storms experienced on the planet. The highest speeds on an average day can be found high in the atmosphere in a region called the jet stream where sustained winds of 55 to 120 km/h (35 to 75 mph) are typical.
Our atmosphere is higher than we think. The 4th layer of earth's atmosphere, the thermosphere, ends at approxinately 60-65 miles from the surface of the Earth. The whole mantle comprises three quarters nitrogen and a quarter oxygen, with tiny traces of other gases. Very close to ground, between 1-8 miles, water vapor and very small amounts of natural gases like CO2, less than 5% of the total 'ocean' that sits above earth, move through it with their own cycles like impurities within the sea. As these are all we detect we tend to imagine that they have a greater effect than they actually do. In fact most weather occurs at jetstream level, in systems that cover huge distances, and can be seen from space as giant swirlings around earth, so far above the earth as to have no contact with the ground. One high pressure system is often the size of Australia and a low pressure zone can span the Tasman Sea. It is this greater thinking mode we must also get into if we are to understand what causes earthquakes. Let us take a brief tour through the solar system and describe the atmospheric weather we would encounter, with half an eye out for planetquakes.
As far as we can tell the moon has a very tenuous atmosphere consisting mostly of byproducts from radioactive decay or bombardment of meteorites and the solar wind. The exact composition is variable and may consist of gases including sodium, potassium, radon, polonium, argon, helium, oxygen, methane, carbon monoxide, or carbon dioxide. There are no tectonic plates on the moon that we know of, but there are moonquakes every time the earth passes close by at times of perigee. The moon has vast areas covered with ancient lava flows. The NASA Apollo missions discovered that there are at least four different kinds of moonquakes: (1) deep moonquakes about 700 km below the surface, probably caused by tides; (2) vibrations from the impact of meteorites; (3) thermal quakes caused by the expansion of the frigid crust when first illuminated by the morning sun after two weeks of deep-freeze lunar night; and (4) shallow moonquakes only 20 or 30 kilometers below the surface.
Mercury maintains a very thin and transitory atmosphere consisting of a varied assortment of gases. Major constituents include potassium, sodium, oxygen, helium, hydrogen, and water vapor. Researchers are not entirely sure what produces this atmosphere, but the leading theory is that it comes from the solar wind, outgassing due to radioactive decay from the surface, and comet impacts. Also, recent evidence has shown that Mercury has a molten core. This suggests a land tide which would impact on what is above the land surface. Mercury and the moon are believed to be no longer tectonically active. The moon has been possibly inactive for the last 3 billion years and Mercury supposedly inactive since about 3.7 billion years ago, yet there are hints of past tectonism. Both bodies have faults where the surface has been broken and pushed on top of itself by compressive forces. In the case of Mercury, the entire planet appears to be covered with a network of these ridges, some over 300 kilometers (185 miles) long, suggesting that Mercury contracted slightly as it cooled. So the jury is out on Mercury, and giving the benefit of the doubt we might grant that seismic activity has occurred and so still may be a possibility.
Venus has the densest and perhaps the most hostile atmosphere of any planet in the solar system. Being closer to the Sun, Venus receives considerably more heating than Earth. The atmosphere is almost entirely carbon dioxide with small amounts of nitrogen and numerous other gases. The dense atmosphere gives the planet a surface temperature hot enough to melt lead and a pressure more than 90 times greater than Earth's. Venus is also surrounded by thick permament clouds of sulfur dioxide and sulfuric acid that form high in the atmosphere from volcanic eruptions at the planet's surface, and block most sunlight from reaching the surface. Temperature remains nearly constant at a blistering 460°C. Wind speeds of more than 300 km/h have been measured at the top of the cloud layer. Hundreds of volcanic features have been mapped on the surface of Venus. Venus shows evidence of huge tectonic activity, volcanism happening now, and where the surface has been, in some locations, stretched and broken, and in other regions, crumpled. Scientists are debating the type of deformation that may be occurring in Venus' interior and how it may relate to the features observed on this planet's surface. Like Earth, Venus and Mars are believed to have hot interiors. This means that they are continuing to lose heat. While their surfaces show evidence of recent deformation — tectonism — neither planet has plate tectonic activity because neither planet has a surface divided into plates. It further means tectonic plates are a red herring. Because Venus has volcanoes it probably has venusquakes.
The Martian atmosphere is very thin with a surface pressure less than 1% that of Earth. The predominant substance composing the atmosphere is carbon dioxide with small amounts of nitrogen and other gases. Temperatures on Mars average only -46°C. The coldest temperatures can be found at the poles during the Martian winter when the surface drops as low as -87°C. This is so cold that as much as a quarter of the atmosphere freezes into slabs of dry ice increasing the size of the polar ice caps. Mars has strong winds and dust storms. Wind speeds as high as 480 km/h (300 mph), greater than anything experienced on earth have been measured racing from the poles towards the equator stirring up great clouds of dust and creating wispy clouds of water ice. Mars is a smaller planet than Earth; it has cooled more, much like a small glass of hot water would cool faster than a large glass of hot water. The outermost layer of Mars is thick, thick enough to support the tallest volcano in the solar system. Much of the tectonic activity on Mars is believed to result from convection in its interior. However, the convection appears to be restricted to a few locations. Hot material may be rising from the interior toward the surface in these locations, causing the surface to bulge, stretch, and crack. The largest of these areas is the Tharsis Bulge. Valles Marineris is a large rift, where the surface has split apart in one of these stretched regions. When the largest volcano in the solar system is Olympus Mons on Mars, we can safely conclude that Mars has had marsquakes in the past and may still be having them.
The atmospheres of all four gas giants, Jupiter, Saturn, Neptune and Uranus are generally similar and are dominated by the gases hydrogen and helium. The atmospheres also contain substances like ammonia, sulfur, and methane that create the colors these planets are known for. These worlds are also quite cold given their distance from the Sun, but all are considerably warmer than the solar energy they receive can account for, which indicates some form of internal stress and therefore heating. The largest single storm ever seen is Jupiter's Great Red Spot that has existed at least as long as humans have been able to observe it. The storm is three times larger than Earth and circles Jupiter's southern hemisphere in just six days. Bearing in mind that if Jupiter was the size of a grapefruit then earth would be the size of a peppercorn, we can imagine the speed this storm might travel. Jupiter is also covered by many smaller storms, some of which appear and disappear within hours while others last for centuries. Similar storms have also been observed on the other gas giants, including Saturn's Great White Spot and Neptune's Great Dark Spot, though these are generally much smaller and less stable than Jupiter's mighty tempests. Jupiter has 63 moons, the largest known number for a planet in our solar system. Europa and Ganymede, moons of Jupiter, have icy crusts that may cover deep oceans. The ice is broken into plates that appear to act like Earth's tectonic plates. In places the plates have slid past each other. In other regions they have ridden over each other. In some locations the ice floes have moved apart, creating a gap that has been infilled by younger ice. Accompanying these turbulent storms are intense winds. Wind speeds of 360 km/h (225 mph) are routine in Jupiter's zonal jets while peak winds can reach 545 km/h (340 mph). Several of Jupiter's moons also possess a thin atmosphere. Io's tenuous atmosphere is primarily made up of sulfur dioxide from volcanic eruptions, but it is quickly stripped away by intense radiation from Jupiter and must be constantly replenished. The atmospheres of Europa and Ganymede are predominantly oxygen, but unlike Earth's oxygen that is created by plants, the gases are generated by charged particles striking the icy surfaces on the moons and splitting water into hydrogen and oxygen. The light hydrogen atoms escape the weak gravitational attraction leaving the oxygen behind. Callisto also has a thin carbon dioxide atmosphere believed to come from the slow sublimation of dry ice on its surface. Jupiter has 5 major moons, the innermost of which is called Io, which is sandwiched between the parent planet and the moons Europa and Ganymede. When Voyager 1 and 2 sped past Jupiter in 1979, scientists were amazed to find that Io is peppered with active volcanoes. We now know that Io is the most volcanically active body in the solar system. The Voyager spacecraft revealed giant calderas up to 200 km (124 miles) across, dozens of erupting volcanoes, and volcanic plumes reaching 500 km (310 miles) above the moon's surface. The stress on Io is gigantic, and it is continually changing shape. Io's land tide is such that its surface rises and falls about 100m per day. Compare that to the ground level of NZ and Australia which sometimes reaches a land tide height variation of 50cms per day. This is a tide created, as for earth, in the solid rock of Io's crust. As Io rotates around Jupiter, the tidal bulge moves, Io's crust is flexed, and tremendous heat is generated - much like the heat generated in a piece of wire when it is quickly bent back and forth. This heat drives the volcanic activity so prevalent on Io.
Whilst Jupiter has 63 moons, Saturn, 6th planet from the sun, has 62. The largest, Titan, is larger than the planet Mercury. Titan's atmosphere is denser and produces a greater surface pressure than Earth's. Composed mostly of nitrogen with small amounts of methane and numerous other gases, the atmosphere reflects most sunlight producing an "anti-greenhouse effect" that cools the surface. This phenomenon makes Titan a very cold world with an average surface temperature of just -183°C (-298°F). In 2005, NASA and the European Space Agency successfully dropped the Huygens lander through Titan's atmosphere to touch down on its frozen surface. Huygens detected very little wind on the surface, but speeds as high as 435 km/h (270 mph) were measured at high altitude. The strong winds appear to be generated by tidal forces from Saturn and produce large wind-blown sand dunes forming in parallel west-to-east lines. Saturn's moon Enceladus emits jets of gas and dust and may harbor liquid water under its south pole region. There appears to be volcanoes in its southern hemisphere that spew geysers of water mixed with nitrogen, carbon dioxide, and methane. We can conclude that Saturn's immediate extraterrestrial enviroment is a seismically active one and that saturnquakes would not be uncommon.
Uranus is the 7th planet from the sun. It has 27 moons. The five major moons are massive enough to have achieved hydrostatic equilibrium, and four of them show signs of internally driven processes such as canyon formation and volcanism on their surfaces. We must accept uranusquakes as a possibility. Winds on Uranus are generally milder because it has less intense bands of clouds than other gas giants, but maximum speeds of 580 km/h (360 mph) have been observed. Winds on Jupiter and Uranus pale in comparison to those of the other gas giants, however. The Voyager 2 spacecraft detected easterly winds on Saturn of 1,800 km/h (1,120 mph). The record for windiest atmosphere in the solar system belongs to Neptune at a whopping 2,100 km/h (1,300 mph).
Triton, a moon of Neptune, is the only moon in the solar system known to be rotating backwards, that is, in an opposite direction to the rotation of the parent planet. Triton has a surface of mostly frozen nitrogen, a mostly water ice crust, an icy mantle and a substantial core of rock and metal. The core makes up two-thirds of its total mass. Although extremely cool, Triton is currently geologically active and erupting. Part of its crust is dotted with geysers erupting nitrogen and methane. There would undoubedly be neptunequakes.
The best-known dwarf planet is the former planet Pluto, near the edge of the solar system. This distant world is believed to be covered in ice that melts as Pluto approaches the Sun in its eccentric orbit. The sublimated gases include nitrogen, methane, and carbon monoxide that form a tenuous atmosphere. As Pluto moves further from the Sun, these gases probably again freeze to the surface. Pluto's atmosphere was first detected in 1985 and has appeared to continued to strengthen through 2002. NASA's New Horizons spacecraft will reach Pluto in 2015 and should be able to directly observe its atmosphere for the first time. So does Pluto, one of the furthest away planetary bodies from the sun, have moons? In fact Pluto has 4 moons. The largest, Charon, is proportionally larger, compared to its primary, than any other satellite of a known planet or dwarf planet in the Solar System. Charon and Pluto are also tidally locked, so that they always present the same face toward each other. Charon seems to be covered with active volcanoes of ammonia-rich water spewing forth from its deep interior. Astronomers at one of the world's great telescopes have separated Charon's dim light from Pluto's and discovered that large areas of the moon's surface are plastered with deposits of crystalline water and ammonia hydrate ice. Such crystalline materials can't last long on an airless world before cosmic rays age and destroy their ordered structure, so they must be replenished regularly. "Some mechanism is renewing Charon's surface, and cryovolcanism is the most probable of the possible mechanisms," write Jason Cook, Steven Desch, Ted Roush, Chad Trujillo, and Tom Geballe in a paper they published this year in The Astrophysical Journal. It is suspected that Charon could have a subterranean ocean. (crystalline water ice & various ammonia hydrates have been detected). Occasionally cracks rapidly form in the crust and water gushes out and crystallises. Are there plutoquakes? So far too little is known. Recent studies have only concentrated on Charon. But as the earth and in the moon are tidally locked and induce shakes in each other, it would be odd if with Pluto and Charon tidally locked Charon was active and Pluto was not. It would be as if our moon was almost as big as Earth and shook violently but did not affect us in any way. That notion is less than plausible.
The largest of the dwarf planets is the recently discovered Eris. Eris likely shares a similar composition as Pluto with large quantities of frozen methane and other ices on its surface. Eris is the largest known object beyond the orbit of Neptune, weighing nearly a third more than Pluto. It travels on an elongated path around the Sun that takes about 560 years to complete. The body follows a very unusual orbit that brings it almost as close to the Sun as Pluto but also far into the outer regions of the solar system. Eris is currently near its maximum distance from the Sun, but as it approaches closer in some 250 years or so, it is likely that some of the ice on its surface will thaw to create a thin atmosphere. It seems that the concentration of nitrogen seems to increase with depth and nitrogen is more abundant closer to the surface. Researchers can't yet come up with an explanation for the difference. The problem is that changes in weather are difficult to explain when Eris is so far from the Sun. Another possibility is that methane and nitrogen vapour erupted from Eris's interior, eventually condensing down to form a new layer of ice. No one is sure whether Eris is warm enough to boast this kind of cryovolcanism, but an eruption cannot be out of the question. After all, Eris has a moon, called Dysnomia.
Ceres and Vesta
Other objects in the solar system that may possess atmospheres include three bodies recently classified as dwarf planets. The closest to Earth is the asteroid Ceres, the largest asteroid in the solar system residing in the belt between Mars and Jupiter. There are indications Ceres may have a thin atmosphere, but its exact nature has yet to be determined. It appears Ceres has an inner core and past volcanism. Vesta is the next biggest asteroid. Do these have moons? NASA is currently looking for them. It is entirely possible for asteroids to have companions.
In addition to the planets, the solar system itself experiences "weather" of sorts. This weather results from conditions at the surface of the Sun that generates solar flares and the solar wind. These phenomena can affect atmospheric conditions and weather on the planets and may also produce interference in Earth satellites and communications systems. This points to a tidal force for all weather on all planets, rather than local, close-to-ground causes. It suggests that weather and earthquakes are "standard practice" for orbiting bodies, and the rotations, oppositions, conjunctions and proximity variations on bodies that all have magnetic fields create stresses akin to stresses between close magnets, and these pressures become tides and the greater explosive tides that we like to call eruptions. It means that earthquakes on earth are the norm, not some anomally. It means they are not really single events but releases of pressure due to daily stresses and flexings that arise from movements and differentials within their electrical fields, due at least in part to rotations and proximities to neighboring bodies and possibly to cycles within. For instance it may be that due to our rotation within an electrical field the interior of Earth may have at least three inner cycles, arising from pressures on the inner core, the outer core and the mantle, and these cycles may interconnect at times more actively than others. We know that some geographic locations are more susceptible because we are aware of geological history, and we know that others off the track receive less activity.
Solving the puzzle
The whole subject is like a jigsaw. There seem to be scattered pieces that we think may be part of the whole. The only way to start to solve a jigsaw is to locate the corners first. In this puzzle there are no corner pieces. We don't even know how many pieces there are. But we do know quakes are not confined to earth. That is a significant find and should alert seismologists to the idea of gravitational stresses from without, acting on the within. That alone should steer them away from tectonic plate gazing. The train comes along the track; the track cannot create a train.