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Mars and Venus

This is a query on Mars. The ferric oxide on the Martian surface contains a lot of oxygen and if heated sufficiently would yield free oxygen. Does the presence of this substance on Mars indicate that at one time there must have been a lot of atmospheric or dissolved (in water?) oxygen available on Mars?

These are my questions about Venus:

1. Why is it that Venus is depicted by Magellan photos as being Red/Orange in colour? If these are radar images how is the "..actual colour of sunlight that reaches the Venusian surface through the thick cloud layer .. " derived? The Magellan images of the surface of Venus are quite bright. Would it really be that bright under such heavy cloud cover?

2. What generates the high velocity (up to 400 km/hr) winds which move from east to west in Venus's upper atmosphere, given that the surface of Venus rotates at a leisurely 6.5 km/hr?

3. What conditions did astronomers expect to find on the surface of Venus before the first probes landed? Thank you for your effort in advance.

Reply

Oxygen is not a rare element, Mars, the Moon, etc. have a lot of oxygen, always combined with other elements into stony stuff. The element that is really important to life is hydrogen. The recent signs that the Moon may have hidden water were exciting not because it is hard to find oxygen on the Moon (it must be separated, of course) but because hydrogen is rare. I am not sure about hydrogen on Mars. Jupiter and other cold big planets of course have plenty, and so do their moons, which may be more accessible. Still, they are pretty far away.

The colors of radar maps on Venus are probably false colors. The color and intensity of sunlight on the surface should be known, because the Russian landers took photos. However, I don't know it.

What drives winds on Venus is not the rotation but the same cause for winds as on Earth--the heat of the Sun. Venus is closer to the Sun, so maybe its atmosphere is more agitated. See the sections in "Stargazers" on sunlight and on the way it creates the Earth's weather
What one observes, in any case, is the wind at the top of the clouds, which might be analogous to the jetstream above Earth, not a good measure of winds at the surface.
I don't know--you must find out by yourself. I know Venus was expected to be "as hot as hell"--but the features of the surface could not be guessed.

Where is the boundary between summer and winter?
This may seem like a silly question but is there a line on the earth where on one side is summer and the other winter? Sort of in the same way that you can go back and forth between two days at the International Date Line.

Reply
Yes, there exists such a line and it is called the equator, but the boundary between summer and winter is not as sharp as the one of (say) the international date line.
Right now it is fall here, but spring in Chile and Argentina, and 2-3 months from now it will be mid-winter here and mid-summer in those countries. At our latitudes, these seasons are well defined. However, a broad belt centered on the equator does not have well-defined summer or winter. The Sun's heat fluctuates somewhat as its noontime passage moves north and south. On the equator, for instance, it passes right overhead around the 21st of March or September, 23.5 degrees off to the north on June 21 and the same amount south of "overhead" (zenith) on December 21.
These small changes do not make much of a change in solar heating. The big difference is made by local climate patterns, e.g. seasonal rains like the monsoon. These countries do not have summer and winter the way we do: for instance, when my daughter visited Darwin, Australia, some years ago, she was told that loacally the year had only two seasons, "the wet" and "the dry. "
The Ozone Hole
I am a auto mechanic and I have one simple question for you. Scientists say there are 2 holes in the atmosphere, ironically they are around the north and south pole, and they blame these holes on chlorine monoxide or refrigerants i.e. fluorocarbons (CFC) escaping into the ozone. Wouldn't the more likely cause of the holes be the magnetic lines of flux? One more quick question: could there be a way of tapping into that magnetic field as an energy source?

Reply
There do indeed exist two "holes" in the Earth's magnetic field, around the MAGNETIC poles, whose magnetic field lines go very far from Earth and afford an easy connection to the solar wind and to interplanetary plasma phenomena. On those lines we do observe "polar rain", a drizzle of fairly energetic electrons (more energy than those of the ionosphere, less than those of the usual polar aurora) which seem to come from the Sun. Also, when solar activity floods interplanetary space with energetic ions and electrons, that is where they are most likely to come down to Earth.
However, the creation and destruction of the ozone layer does not involve the magnetic field. Instead, its factors are chemistry and sunlight, and the "ozone hole" is around the geographic pole, not the magnetic one.
The ozone layer is maintained as an equilibrium between creation of ozone by ultra-violet sunlight, and its destruction by various natural processes (this is not my field, and I do not know details). During polar winter, the polar cap is dark and ozone is not created, just destroyed (a bit further from the pole, with just a few hours of sunlight and the sun shining at a shallow angle, ozone creation is also reduced). The observation of an "ozone hole" in recent years suggest accelerated destruction, as predicted by Rowland and Molina to come from chlorine in man-made substances.
As for tapping electric currents from space, I don't think it will work, because (1) they are very spread-out, by our standards--how can you tap a current sheet 100-1000 miles wide?; and (2) between us and them lies the atmosphere, a very effective electric insulator--as is well known to power companies, which string their high-voltage cables through air without worrying about the power leaking away.
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What keeps the Sun from blowing up?
Dear NASA, I have a question abour the sun. We all know that the sun is powered by thermonuclear fusion reactions,so why doesn't it explode like an H-bomb?

Reply
What keeps the Sun from blowing up? Gravity.
The Sun is not exactly like an H-bomb--the bomb has fuel that is easier to "burn, " while to Sun "burns" ordinary hydrogen--but there does exist a similarity. Why does a hydrogen bomb explode? Because an enormous amount of energy is released in a short instant and inside a small volume, heating the material to extreme temperature. The material expands forcibly, creating a powerful shock, and that is the explosion.
The Sun releases much more energy every second in its central regions, but those materials are under great pressure, from the weight of all the matter piled up on top of them--the thick outer layers of the Sun, pulled down by a gravity much stronger than anything on Earth. That pressure confines the extremely hot gas in the Sun's core. The heat gradually works its way to the surface, but the Sun does not blow up.
If somehow it could yield to the pressure and expand, the central core would cool down and the nuclear energy release would drop. Then the pressure would decrease again and gravity would reassert itself. Some stars do in fact oscillate, but we should be grateful that the Sun does not belong to that class.
See more in http://www.phy6.org/stargaze/Sun7enrg.htm
Those glorious Southern Skies!
Not long ago I visited Chile for the first time and observed the night sky there. At that latitude, the centre of the Milky Way passes overhead, where it makes a grand show...
Why is there such a difference between Southern and Northern Hemisphere? Is it because of the 23 1/2 degree tilt?

Reply
Why such a difference between the southern and northern hemisphere? Because from the point of view of the Earth, all stars are so distant that they appear as if they were attached to a tremendously large sphere, with us in the middle.
At night, standing on the ground, you only see HALF the sphere. If you stood at the NORTH pole, half the sphere would be all you ever saw, appearing to spin around the point right overhead, the zenith. Standing at the SOUTH pole, you would see the other half, spinning around the point overhead, which is on the OPPOSITE end of the sphere from the overhead point at the north pole.
If you lived on the equator, the two poles of the sky would be on opposite sides of the horizon, and as the sphere of the heavens rotated around them, you would in principle see ALL the stars, sooner or later. In practice, those close to the poles will be near the horizon and not easy to see.
Maryland, where I live, is somewhere between the north pole and the equator, so the stars near the north pole are easily seen, and we get to see some stars of the southern hemisphere as well, though not those near the southern pole of the heavens (like the Southern Cross and Alpha Centauri), and many southern stars are only seen here near the horizon.
Similarly, from Chile you won't see the Pole Star, the Big Dipper or Cassiopeia, but the bright stars near the southern pole more than make up for them, and yes, the brightest part of the Milky way is there, too. North of the equator, the best view of the Milky Way is in mid-summer.
The 23 1/2 degree tilt has to do with the way the Sun, Moon and planets appear to move--not with the apparent motion of the distant stars.
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Should we fear big solar outbursts?
I have a question pertaining to your studies in the upcoming year, particularly surrounding the forecast Solar Maximum.
I have heard about the upcoming Solar Maximum starting soon (CNN.com article, Nov. 11, 1999). I have also heard (unofficially), that there could be a very large solar storm near the end of April.
Finally, it is relatively commonly known that there is going to be an unusual alignment of the planets in our solar system at the beginning of May, 2000. Has there been an in-depth study to determine effects of the combination of these phenomena, and the potential impacts on both our solar system, and our planet?
The real question; could this combination of phenomena:
1.) Promote a solar flare, or SME, significantly larger than previously experienced in recorded history?
2.) Disrupt the crust of our planet, creating a significant amount of tectonic activity, and if so, by how much?
3.) Potentially disrupt our magnetic field severely with the combination of solar magnetic and gravitational forces?
No calculations, or in-depth study has occurred, but I have a hunch this should be looked at more closely, and by qualified people.

Reply
Your message made me once more appreciate the amount of misleading and loose information circulating on the web. I have spent a great deal of time and thought on creating a web site describing what is known about the magnetic field of the Earth and the Sun's effects on it, and for a real understanding, you better look there:
http://www.phy6.org/Education/Intro.html
To answer your questions in brief: The solar maximum is already here [December 1999]. It is not an abrupt event you can date, but the crest of a wave whose width is at least several years. From what I have heard, the current peak is lower than expected.
No one can predict a large solar storm months ahead of time--the best we can say is that they are more frequent near the peak of the sunspot cycle. Some big ones cause little disturbance near Earth--depends on factors like the precise orientation of the interplanetary magnetic field. Planetary alignments have no effect whatsoever. [See also next item.]
The large planets you read about are unlike anything in the solar system --usually Jupiter-size or bigger, and very close to the star (this has to do with the method of detection--it's hard to detect long-period planets).
No solar eruption has ever been found to affect the solid Earth. Their energy is too small, and almost all of it is dissipated outside the breathable atmosphere. No earthquakes follow CMEs.
I have no control over CNN. But if you seek to understand nature, look up my site and sources linked or cited there.
Happy new century
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Planetary line-up and the sunspot cycle
Enjoyed browsing through some of your efforts on the Web. I am hoping you could help settle some of my thoughts before I make a fool of myself.
In your experience, has anyone tried to correlate lineups of the sun, earth and major planets' magnetospheres with the sunspot cycles? My spare-time effort found some correlation between lineups and cycles in a number of years. My wonderment centers around the possibility that some forces of the planets when lined up, possibly relating to their magnetospheres, impact the suns magnetosphere causing a solar max. I've also considered the possibility that related magnetosphere effects could be the cause of previous polar reversals on the earth. Additionally, ringing of our magnetosphere might impact charged tectonic plates...but that is again another direction. Only if you have time, please comment.

Reply
There exists a tempting closeness between the length of the solar cycle and the orbital period of Jupiter, but I don't think the two are related. I cannot imagine any mechanism coupling the two-- especially since the Sun rotates in about 27 days, so the relative period of Jupiter going around the Sun is of that order. Furthermore, the solar wind moves with supersonic speed, which means that solar disturbances can (and do) travel downstream with it, but disturbances from a planetary magnetosphere (whatever they might be) don't easily propagate sunward.
Above and beyond all these, there is always the question of energy-- the currency in which the price of any physical process must be paid. The energy required in the solar cycle is much bigger than anything planetary magnetospheres can supply.
So what causes the cycle? The Sun rotates unevenly, slower near the poles, faster near the equator, probably because of the way gas flows in it (Jupiter also has such a difference). In a magnetized hot gas, this difference deforms and amplifies the magnetic field, and there exist some general theories of the sunspot cycle based on this, although many details remain unclear. The general idea is that as the magnetic field gets amplified, it forms concentrated "ropes" which push out the hot gas, and when they reach a certain strength, enough gas is displaced that the ropes are light enough to float to the surface, where they are seen as sunspots.
Again, the magnetosphere is a relatively weak influence on the Earth's internal magnetism--even a big magnetic storm only reduces the surface equatorial field by 1%. Furthermore, the time scale differs--reversals happen on time scales of 0.5-1 million years, while magnetic storms have a 1-day scale or faster.
What seems to be involved are the currents which circulate in the Earth's core, presumably driven by flows there, which (like flows on the Sun) get their energy from heat. The magnetic field is fairly complicated--the 2-pole structure we see (north-south) is dominant, but not by as much as it seems, because more complicated modes get filtered away faster by distance. Right now the 2-pole field is declining at about 5-7% per century, but the late Ed Benton has shown that the more complex parts are gaining energy, and the total sum is fairly constant. Maybe, when a reversal occurs, for a while the 2-pole part gets small and the total field is rather complex (4, 8 poles..), and when the simple pattern re-emerges, it is reversed.
Anyway--keep studying, keep up your sense of wonderment
What are comet tails made of?
Are comet tails the reult of melting and evaporation of ices from the comet core or are they dust collected by the comet as it moves in its orbit?

Reply
Comet tails contain both evaporated ices and dust, as explained in the section "Comet Tails and the Solar Probe" near the end of the file http://www.phy6.org/Saberr.htm
The dust however is not collected by the comet in its orbit, but is part of its make up, probably dating back to the beginning of the solar system. Comets may have two tails, and sometimes these are well separated, as in the recent Comet Hale Bopp: they differ in color, composition, and direction, and are pushed away from the Sun by different forces.
Dust tails are pushed by light pressure, and their colors are those of sunlight, scattered by them the way clouds on Earth also scatter sunlight. The other tails contain plasma--free electrons and ions, that is, atoms from which sunlight has removed one or more electrons, leaving a positive charge. They glow in the colors characteristic of their material (a bit like the way streetlights produce the characteristic glow of sodium), and are pushed back by the solar wind. As explained on the above web page, the velocity of the solar wind is not too many times larger than that of the comet, and that causes them to point not straight away from the Sun but at a small angle to that direction.
See also htpp://www.phy6.org/Education/wsolwind.html
David
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If light speed sets the limit, why fly into space?
Dear sir
I have a question as to space travel. What is the point in exploring space? Is it just for achievment purposes or in the future will man discover LIGHTSPEED? Because otherwise, the whole thing seem rather pointless. It is rather like asking a garden snail to tour America in it`s own lifetime. Can you put any light on this question?.

Reply

From all we know, achieving lightspeed or anything close to it is well beyond today's technology, and I suspect, tomorrow's as well. The purpose of exploring space is different--to expand humanity's reach, and to understand the universe in which we live. Ancient humans may have been content to see the sun, moon and stars rise and set without caring what they were, or how distant. We have come a long way from then--to electricity, cars, airplanes and the internet--essentially, because humans want to understand more. Most Americans would probably feel rather stale if no progress happened over their lifetimes--just different teams making it to the superbowl, different wars being fought overseas. I for one felt excited by the landing on the moon, by the first pictures from Jupiter and Neptune, and of the sun in X-rays (quite different from the bland disk we see). I also feel excited by evidence of distant planets and giant black holes at the center of galaxies. No, I don't think we'll get there in my lifetime or in the next 1000 years--but humanity has a longer timetable, much longer than that of any individual.

Does precession mis-align ancient monuments?
Dear Mr Stern,
I live in Ireland. There is an ancient monument at Newgrange in this country which was constructed some 5000 years ago. The particular alignment of the monument to the sun allows an inner chamber to be lit by the sunrise at the winter solstice. The construction of such a building so long ago with such accuracy seems almost incredible to me.
I have a query however. Is the tomb doomed to a long darkness in the future due to precession?

Reply

Look at the above figure, taken from the web page http://www.phy6.org.stargaze/Sseason.htm about the seasons of the year, in section #3 of ""Stargazers." It shows the relation between the Sun and the Earth with its tilted rotation axis, throughout the year (north is up). That relation is what varies the length of the day and the apparent motion of the Sun across the sky, from season to season.
Imagine you were able to rotate this arrangement by some angle--by 10°, 30°, 90° or whatever--around an axis perpendicular to the plane of the ecliptic. You rotate just the Earth and its orbit (and perhaps the Sun), while the rest of the universe stays as it is.
The relation between the Sun and the Earth then remains exactly as before--the only difference is that you are looking at it from a different direction. Seasons and the apparent motion of the Sun across the sky are still the same as they were.
What our imaginary rotation has done is exactly the same as what the precession of the equinoxes does to the Earth's axis. So if an ancient monument is lined up to point at the Sun during solstice, it will continue doing so. Our calendar is also adjusted, so it would also remain the same day of the year.
On the other hand, an ancient monument aimed at a certain passage of a star would no longer fulfil its function, because now the axis of the Earth points towards a different part of the celestial sphere.
David