Venus Science |
Venus Science |
Guest_BruceMoomaw_* |
Feb 13 2006, 10:37 PM
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#16
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I knew some (but not all) of what Ed Strick says about the partial foulup of Mariner 2's radiometry; thanks for the new details, Ed. I gather there was also some electronic "cross-talk" in its circuitry that had to be sorted out, with the result that the conclusions weren't announced until three months after the flyby. The conclusions turned out to be pretty accurate, though. (The National Geographic did an article at the time with a picture showing the locations on the Venusian disk of those 22 measurements the radiometers did make. Calling it a "crude" image is the understatement of the year.)
As for the Mars 3 failure, V.S. Perminov, in his history of the Mars program (with which he was intimately associated), doesn't mention an orbiter failure, and instead suggests that an electrostatic discharge from the powerful dust storm in which the lander touched down may have knocked it out. And a set of articles in "Spaceflight" from a St. Petersburg-located correspondent suggest that the failures of some earlier planetary craft were due to: (1) Immediate failure of a cooling unit on Venera 1, so that its electronics quickly overheated. (2) First-day loss of all of Mars 1's attitude-control nitrogen due to a leak. The Soviets knew on the first day that it couldn't make it to Mars, so they put it into a slow spin-stabilized roll to see how long they could maintain contact with it -- and thus briefly held the distance record for long-range radio communication. (3) Quick loss of the internal pressurization of Zond 1's electronics compartment, presumably leading to the electronics being knocked out by the resultant internal temperature extremes. |
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Feb 14 2006, 09:52 AM
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#17
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Senior Member Group: Members Posts: 1870 Joined: 20-February 05 Member No.: 174 |
The soviets immediately <speculatively> blamed the Mars 3 failure on the great 1971 global dust storm. Unfortunately, that blame game has a bit of a hole in it. While I'm sure there are pretty impressive turbulent horizontal velocities during the expansion phase of a dust storm, by the time of the Mard 3 landing, the storm had entered the essentially quiescent phase.
The storm started in ?late August? 71 ?or early September? and became the only truely global dust storm so far recorded. Not just "globe-encircling" but global! (usually one or both polar regions remain fairly clear). But by late October or so, the atmosphere was relatively uniformly filled with dust and the strong thermal gradients between sun-heated dusty atmosphere and dominately surface-of-Mars-heated less-dusty atmosphere was gone and both models and observation indicate winds had died down. I don't recall whether Vikings saw less wind during high opacity periods or not.... I think during the second storm, it shut down some thermally driven tidal mode of atmosphere "sloshing" or shut down cold fronts out of the winter northern plains. Regardless.... when Mars 3 landed, there was a global dust storm, but "Raging" it was not. The Mariner 2 microwave radiometer results were published in (I think) Journal of Geophysical Research. They took the measurement points, convolved them with the instruments in-flight calibrations and known "time response function" (there was lag in it's response to reduce random noise) and calculated the actual observation brightness temperatures. You could take the data, calculate an interpolated series of brightnesses, and plot it in sky coordinates to actually get a quasi image. I've seen worse. I've MADE worse and found them useful. |
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Feb 14 2006, 04:35 PM
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#18
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Senior Member Group: Members Posts: 2454 Joined: 8-July 05 From: NGC 5907 Member No.: 430 |
Sunspot, NM (Feb. 7, 2006) -- The planet Venus is best known for the thick layers of clouds that veil its surface from view by telescopes on Earth. But the veil has holes, and a New Mexico State University scientist plans on using a solar telescope to peer through them to study the weather on Venus. "Observations of Venus from a nighttime telescope at a single location are very difficult because Venus is so close to the Sun in the sky," said Dr. Nancy Chanover, a planetary scientist at NMSU in Las Cruces, NM. "You can observe it for about two hours at most." Then the Sun rises and blinds the telescope (or Venus sets, depending on the time of year). http://www.nso.edu/press/venus06/ VENUSIAN HEAT - Filter Problems Hamper Venus Observations http://www.spacedaily.com/reports/Filter_P...servations.html Sunspot, NM (SPX) Feb 13, 2006 - Instrument problems have kept the team at the Dunn Solar Telescope from observing the planet Venus as they had hoped. "The filter on our infrared camera is leaking thermal radiation and keeping us from observing the planet," said Nancy Chanover, principal investigator from New Mexico State University. -------------------- "After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance. I see that such intercourse long continued would make one thoroughly prosaic, hard, and coarse. But the longest intercourse with Nature, though in her rudest moods, does not thus harden and make coarse. A hard, sensible man whom we liken to a rock is indeed much harder than a rock. From hard, coarse, insensible men with whom I have no sympathy, I go to commune with the rocks, whose hearts are comparatively soft." - Henry David Thoreau, November 15, 1853 |
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Feb 22 2006, 04:09 PM
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#19
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Senior Member Group: Members Posts: 2454 Joined: 8-July 05 From: NGC 5907 Member No.: 430 |
Science/Astronomy:
* Planetary Protection Study Group Mulls Life On Venus http://www.space.com/scienceastronomy/060221_venus_life.html A special study group has advised NASA that Venus is far too hellish of a world for life to exist on or below the planet's surface. Furthermore, while the potential for life in the clouds of Venus can't be ruled out, the expert panel gauged this possibility as extremely low. -------------------- "After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance. I see that such intercourse long continued would make one thoroughly prosaic, hard, and coarse. But the longest intercourse with Nature, though in her rudest moods, does not thus harden and make coarse. A hard, sensible man whom we liken to a rock is indeed much harder than a rock. From hard, coarse, insensible men with whom I have no sympathy, I go to commune with the rocks, whose hearts are comparatively soft." - Henry David Thoreau, November 15, 1853 |
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Feb 22 2006, 04:21 PM
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#20
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
A special study group has advised NASA that Venus is far too hellish of a world for life to exist on or below the planet's surface. Furthermore, while the potential for life in the clouds of Venus can't be ruled out, the expert panel gauged this possibility as extremely low. Well, the lava-drinkers who have built glorious cities all over Venus will be surprised to hear this. Aside from the acid problem, and the finite nutrition in a droplet, the problem with cloud-life, on Venus or elsewhere is that turnover will lead individual droplets to undergo harsh temperature changes. The usual issue with life and extreme conditions is that it's one thing for life to originate in an accomodating niche and spread/adapt to a harsher one, but another for it to originate in a place with narrow margins. The best hope for life in the Venusian clouds would be if it once existed on the surface, before Venus lost its H2O and gained its CO2 and heat (if there was a time before that), spread to the clouds, and adapted to the massive changes that took place in the meantime. This seems less likely than fossilized life on Mars, but any attempt to prove that mathematically would require some assumptions with little basis in fact. |
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Mar 23 2006, 03:32 PM
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#21
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Senior Member Group: Members Posts: 2454 Joined: 8-July 05 From: NGC 5907 Member No.: 430 |
I also get a small thrill out of looking at a planet in the night sky
and knowing that one of humanity's probes is there exploring it at that very moment. I particularly recall when Mars Pathfinder landed on Mars on July 4, 1997. I was outdoors watching a fireworks display when between the artificial explosions I could see the Red Planet shining fairly bright in the dark sky. And I knew right at that moment that the first machine in 21 years was just getting down to business on that world. Now we can do the same for Venus and Venus Express: NOW IS THE BEST TIME TO SEE VENUS THIS YEAR Astronomy Magazine Press Release WAUKESHA, WI — The “morning star” Venus lights the sky before dawn, heralding spring’s arrival. On March 25, the brilliant planet reaches its greatest western elongation — when the planet is as far west of the Sun as possible. Then, it sits just above the horizon in the east-southeast sky 2 hours before sunrise. Look for the waning crescent Moon passing to the right of the “morning star.” Venus will be the bright object just to the upper left of the Moon. Each day thereafter, Venus’ sky position sinks closer to the horizon. Venus shone at its brightest, magnitude –4.6, in February, but the planet will dominate the morning sky throughout summer. Take a Look To the naked eye, Venus’ light rivals only moonshine in the early morning sky. But you can use a telescope to watch as the planet changes phases, like the Moon’s, during the year. By March 25, its globe measures 25" through a telescope and has fattened to half-lit. It’s at its brightest for the year now; even though the phase increases, its angular size decreases as the Earth-Venus distance increases. Venus’ Orbit Our “sister planet” lies an average of 67 million miles (108 million kilometers) from the Sun. Because Venus lies closer to the Sun than Earth, it always appears close to our star in the sky. On March 26, Venus and the Moon help you spot a rarely seen planet: Neptune. At about 5 a.m. local time, Venus appears slightly north of (above) Neptune. The Moon lies just below and to the left of the planets. Quick Facts - Venus orbits the Sun in 225 days. - The planet is about 7,521 miles (12,104 km) in diameter, or 95 percent the size of Earth. - Venus spins on its axis once every 243 days, but it spins in the opposite direction of Earth — on Venus, the Sun rises in the west and sets in the east. - Venus’ atmosphere is thick sulfuric-acid clouds, which reflect sunlight extremely well. - The surface temperature on Venus can approach 900º Fahrenheit (482º Celsius); it’s the hottest place in the solar system after the Sun. - In Roman mythology, Venus was identified with the goddess of love and beauty, Aphrodite. To the ancient Mayans, Venus was the patron planet of warfare called Kukulcan (the feathered serpent). Also in the Sky - Throughout March — Saturn lies high in the southeast. An hour after sunset, the ringed planet shines at magnitude 0 and stands among the faint stars of Cancer the Crab. - Through the end of March — Jupiter can be spotted in the southwest sky in the predawn sky. - Wednesday, March 29 — A total solar eclipse darkens the sky over northern Africa and Asia. Astronomy magazine is leading two tour groups through the eclipse path. Visit Astronomy.com for special coverage. -------------------- "After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance. I see that such intercourse long continued would make one thoroughly prosaic, hard, and coarse. But the longest intercourse with Nature, though in her rudest moods, does not thus harden and make coarse. A hard, sensible man whom we liken to a rock is indeed much harder than a rock. From hard, coarse, insensible men with whom I have no sympathy, I go to commune with the rocks, whose hearts are comparatively soft." - Henry David Thoreau, November 15, 1853 |
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Mar 25 2006, 06:47 PM
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#22
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Member Group: Members Posts: 159 Joined: 4-March 06 Member No.: 694 |
Off course, we (depending on location) got a chance to see Venus transit the sun on June 8, 2004. We will (again, depending on location) will get to see another one on June 5-6, 2012.
-------------------- I call heaven and earth to witness against you this day, that I have set before thee life and death, the blessing and the curse; therefore choose life, that thou mayest live, thou and thy seed.
- Opening line from episode 13 of "Cosmos" |
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Apr 10 2006, 03:48 PM
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#23
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Senior Member Group: Members Posts: 2454 Joined: 8-July 05 From: NGC 5907 Member No.: 430 |
"VENUS' CLIMATE IS TELLING US THAT WE REALLY DON'T UNDERSTAND THE EARTH"
The Observer, 9 April 2006 Venus: the hot spot This week a European spacecraft will arrive for a date with Venus, our closest planetary neighbour. Scientists hope the mission, made on a shoestring budget, will reveal vital lessons on how unchecked greenhouse gases can turn a world into a blistering Hades. Robin McKie reports on a journey to the Forgotten Planet On Tuesday morning, mission controllers in the European Space Agency's operations centre in Darmstadt will put the finishing touches to an international bid to study the ultimate neighbour from hell. They will transmit a series of radio commands to a robot spacecraft currently hurtling towards the Sun. Its rocket engine will fire for 50 minutes as it passes Venus, slowing the craft down so that it can be captured by the planet's gravitational field. Once in orbit, the wardrobe-sized probe - Venus Express - will then study the planet's acid clouds, searing heat, crushingly dense atmosphere and hurricanes to find out why Earth's nearest neighbour has become a place of insufferable heat and poison. 'Venus is very like Earth in that it is the same size and has an orbit round the Sun close to ours,' said David Southwood, head of science at the ESA. 'Yet Venus went wrong. We did not. We want to find out why Venus became our evil twin.' Venus and Earth are almost identical in size. In addition, both orbit the Sun in 'the Goldilocks zone', a swath of space in which conditions are considered by astronomers as being not too hot and not too cold to prevent the evolution of life. Venus should make ideal planetary real estate, in other words. Yet it is the solar system's most inhospitable planet. 'It's very disturbing that we do not understand the climate on a planet that is so much like the Earth,' said Professor Fred Taylor, a planetary scientist based at Oxford University and one of the ESA's chief advisers for the Venus Express mission. 'It is telling us that we really don't understand the Earth. We have ended up with a lot of mysteries.' Full article here: http://observer.guardian.co.uk/uk_news/sto...1750001,00.html -------------------- "After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance. I see that such intercourse long continued would make one thoroughly prosaic, hard, and coarse. But the longest intercourse with Nature, though in her rudest moods, does not thus harden and make coarse. A hard, sensible man whom we liken to a rock is indeed much harder than a rock. From hard, coarse, insensible men with whom I have no sympathy, I go to commune with the rocks, whose hearts are comparatively soft." - Henry David Thoreau, November 15, 1853 |
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Apr 13 2006, 09:28 PM
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#24
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Member Group: Members Posts: 362 Joined: 13-April 06 From: Malta Member No.: 741 |
Unnecessary quote removed - moderator
My biggest query about Venus is that despite the lack of magnetic field and hence complete exposure to atmospheric erosion by the solar wind,Venus has managed to retain a thick atmosphere.Could this be indirect evidence for continued volcanic activity on the planet??!! |
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Apr 14 2006, 09:30 AM
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#25
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Senior Member Group: Members Posts: 1870 Joined: 20-February 05 Member No.: 174 |
I don't know the exact modelling based on Venera 9 and 10 and Pioneer Venus Orbiter solar wind interaction data, supplemented by Galileo/Cassini flyby data, but I think it boils down to there being significant erosion has occured, but it's still quite a small fraction of the total atmosphereric mass.
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Guest_BruceMoomaw_* |
Apr 14 2006, 07:01 PM
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#26
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Guests |
Venus has both a much greater mass than Mars (about 8 times more), and much more volcanic activity over its total history than Mars. Thus the ability of the solar wind -- even though it's much stronger at Venus than at Mars -- to strip away atmospheres has done far less to reduce Venus' total atmospheric mass than it did for Mars.
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Apr 14 2006, 07:55 PM
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#27
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Senior Member Group: Members Posts: 1636 Joined: 9-May 05 From: Lima, Peru Member No.: 385 |
Venus has both a much greater mass than Mars (about 8 times more), and much more volcanic activity over its total history than Mars. Thus the ability of the solar wind -- even though it's much stronger at Venus than at Mars -- to strip away atmospheres has done far less to reduce Venus' total atmospheric mass than it did for Mars. And also the Venus' greater gravity than Mars might influence in some degree to the clouds formation? Mars has lost much of its atmosphere due to low planet gravity as one of the factors? Rodolfo |
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Apr 14 2006, 11:43 PM
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#28
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Senior Member Group: Members Posts: 2454 Joined: 8-July 05 From: NGC 5907 Member No.: 430 |
My biggest query about Venus is that despite the lack of magnetic field and hence complete exposure to atmospheric erosion by the solar wind,Venus has managed to retain a thick atmosphere.Could this be indirect evidence for continued volcanic activity on the planet??!! Not long after Pioneer 12 (aka, Pioneer Venus Orbiter) arrived at the Cloudy Planet in late 1978, it detected a recent drop in the amount of sulfur dioxide in the planet's thick atmosphere, which was interpreted as the result of volcanic activity. Examining various radar images, especially from Magellan, has anyone ever seen any flow patterns or other changes that might have indicted an active volcano or two? -------------------- "After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance. I see that such intercourse long continued would make one thoroughly prosaic, hard, and coarse. But the longest intercourse with Nature, though in her rudest moods, does not thus harden and make coarse. A hard, sensible man whom we liken to a rock is indeed much harder than a rock. From hard, coarse, insensible men with whom I have no sympathy, I go to commune with the rocks, whose hearts are comparatively soft." - Henry David Thoreau, November 15, 1853 |
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Guest_DonPMitchell_* |
May 5 2006, 02:37 AM
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#29
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A few comments on the Russian probes:
Venera-1 - the temperature control system did not fail, but photosensitive element in the precision solar sensor overheated. It automatically put itself into a backup mode of spin stabilization, but contact was lost after the third telemetry session. They made an attempt to send a Mars-1 style photo-flyby in 1962, and two attempts to send a Zond-3 style probe in 1965. Two failed to leave parking orbit, Venera-2 lost communication just before it was to relay all of its recorded data, including the photos. It may have actually performed its mission objectives, we will never know. Mars-1 - a faulty valve caused a slow leak of its attitude control nitrogen. Before loss of control, it was placed in a backup mode of spin stabilization, and space science was performed for about half its flight, until contact was lost. If I was going to guess, I'd say it wobbled out of alighnment or the Earth just passed out of the funnel-shaped radiation pattern of its semi-directional antennas. Zond-1 lost internal pressurization. From attitude pertubations, Soviets calculated that the window of its astronavigation sensor cracked. The ground crew then made a fatel mistake -- they switched on the radio transmitter before the craft was completely evaculated, and corona discharges destroyed the radio in the main bus. A back-up system switched over the main antenna to the transmitter in its landing capsule, and it continued for quite some time after that. Several midcourse corrections were performed, space science data was returned, but they lost contact before it reached Venus. In theory, it could have achieved its primary objective (landing) if they had not lost contact. Zond-2 a photoflyby, not a lander. Its solar panels only half deployed, and lack of power ruined the mission. Zond-2, Zond-3 and Venera-2 were essentially identical spacecrafts. |
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Guest_DonPMitchell_* |
May 5 2006, 02:52 AM
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#30
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A couple comments on Mariner -2 and -5
I think it was a good call that NASA put the radio occultation experiment on Mariner-5. That ended up being the key experiment that mattered. In particular, it gave an important sanity check to the Venera-4 results about the depth of the atmosphere. Due to altimeter ambiguity, it was believed at first that Venera-4 had landed, and nobody would have disputed that without the occultation data. I think this was more valuable than noisy 256x256 television pictures, which probably wouldn't have shown much. There is a nice little book about the Mariner-2 mission published by JPL (Mariner: Mission to Venus), and lots of scuttlebutt about it. Mariner-2 just barely made it to Venus, and the inside joke then was that JPL stood for "Just Plain Lucky". Mariner-2 was a refurbished Ranger probe, a notoriously unreliable spacecraft. It's ironic that one of them made it to Venus two years before the first one succeeded in a lunar mission. The failure of about a dozen Lunar probes by that time was the cause of a congressional investigation and management shake-ups at NASA. Of course, the Russians had similar probems, and Korolev was called on the carpet at the Kremlin about the same time. They had a series of failures in their even more ambitious program to soft land on the Moon (Luna-4 to 8). Politicians and the public just didn't undestand how difficult and fundamentally new all of this work was. By the time Mariner-2 reached Venus, the temperature of its body was unknown because it had exceeded the range of its sensors. Somewhere in excess of 100 C. The radiometer was so hot (60 C) that it almost couldn't function. One of its two solar panels had failed, its astro-navigation sensor was going blind and was only at a few percent of signal by then, etc. Yup, just plain lucky! But nevertheless a milestone in space history. |
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