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00:00The planet closest to Earth and second from the Sun is Venus.
00:22Sometimes Venus has been called Earth's twin, but the second planet is far from being our
00:27world's twin, as we will see in this program.
00:57I'm Larry Ross, Director of Space Programs at NASA's Lewis Research Center in Cleveland,
01:17Ohio, and I'm your host for this third program in a series of 13 called Journey Through the
01:23Solar System.
01:25Now let's go to a NASA film called Venus Pioneer.
01:29Radar which can penetrate the clouds reveals Venus to be a nearly perfect sphere, close
01:34to Earth in size and density.
01:37While Earth tilts some 23 degrees, the axis of Venus is nearly vertical, and its orbit
01:42around the Sun is nearly circular, so it should have no seasons.
01:46It rotates backwards, or retrograde, so slowly that one Venusian day equals 243 Earth days.
01:54In fact, a Venusian day is longer than a Venusian year.
01:58Somehow its rotation is synchronized with Earth's, so that it always shows the same
02:03face to us whenever it swings closest.
02:08The major mysteries are in its atmosphere, a 70-mile thick blanket of nearly waterless
02:13carbon dioxide so heavy that surface pressures are 90 times that of Earth.
02:19The surface temperature is an astounding 900 degrees Fahrenheit, twice as hot as an oven.
02:24The dark markings in the cloud tops move some 50 times as rapidly as the solid planet,
02:29and the clouds themselves appear to contain sulfuric acid.
02:34Earth-based radars reveal only crude hints of the surface beneath the clouds, vague outlines,
02:40but no clue on whether they are high or low regions.
02:45The first pictures from the surface of a boulder-strewn Venus were made by the Russian Venera spacecraft,
02:51an ongoing series of probes.
02:54Such was our knowledge of Venus in the year 1978, but that state of affairs would change
03:00radically because of the National Aeronautics and Space Administration's most comprehensive
03:05study of the atmosphere of another planet, Pioneer Venus.
03:09Two coordinated missions, a task force of six spacecraft, one mission to orbit Venus
03:15for a full year or more, while the second sends five instrumented probes down through
03:20the clouds for simultaneous measurements over much of the planet.
03:25This is how it happened.
03:31An introductory question, how can the study of Venus shed light on our earthly problems?
03:36One of the things we're looking for from this kind of study is the ability to do something
03:42that the laboratory scientists can do, well, to substitute for what he can do.
03:47He can experiment.
03:49He can try different conditions to see whether his theories are going to work out.
03:52If you're just dealing with the Earth, you're just dealing with one body like the Earth,
03:56you don't have this ability to experiment.
04:00In principle, you could start changing the Earth's atmosphere, and I don't think that
04:03would be very much appreciated, and I don't think it's a very sensible way to test out
04:07our theories.
04:08So generally, we're stuck with the atmosphere as it is, and consequently, planetary research
04:15can fill this gap to a certain extent, and we particularly look for examples and take
04:22specific interest in examples, which to some extent fill this role by giving us phenomena
04:29which look very similar to a terrestrial phenomenon in some way, in some fundamental way, and
04:34yet are very clearly different.
04:37And then if our theories, which we've worked out for the Earth, can cope with that circumstance,
04:42then we can be rather confident about them.
04:46May 1978.
04:48The Pioneer Venus Orbiter, first of the pair of missions, is at Kennedy Space Center for
04:53final preparations.
04:55It will carry a dozen instruments, a total of 100 pounds.
04:59Befitting a visit to a goddess, Orbiter is robed in gold-plated blankets, the best-known
05:04reflector of unwanted heat.
05:10This chariot, a reliable Atlas Centaur, great-grandson of America's first intercontinental missile
05:16and booster for the first Americans in orbit, it's still a mighty sight at liftoff.
05:41Setting off on a leisurely route to Venus, the orbiter chases its target more than halfway
05:53around the solar system, en route for more than half an Earth year.
06:05From its birthplace, the Hughes Aircraft Company's Space and Communications Group in El Segundo,
06:10California, the hydra-headed multiprobe also goes to the Cape.
06:14Here in last-minute preparations for launch, it meets the press.
06:18In all, 18 science experiments ride the five parts of the multiprobe.
06:23Today this heat shield and the so-called sounder probe instrument ball it protected lie as
06:29scorched debris on Venus.
06:31Last chance for pictures.
06:34It also carries precious cargo to Venus, including this diamond, ground into an instrument
06:40window.
06:41Diamond is the only infrared transparent substance that can withstand the heat and pressure of
06:46the Venus atmosphere.
06:48Multiprobe's turn comes the night of August 8, 1978.
07:05The proverbial homesick angel, it sheds Earth's gravity to chase the orbiter more than 11
07:12weeks ahead.
07:18On this cosmic merry-go-round, the multiprobe takes a different route through the gravity
07:22wells to arrive at Venus only five days behind orbiter.
07:26Near the planet, it will release the large sounder probe and three small probes.
07:31The drum-shaped bus itself comprises the fifth probe.
07:35It will burn out in the cloud tops.
07:37But first, the orbiter must be trapped into its proper orbit, the first moment of truth.
07:46Orders for this complex maneuver originate here at NASA's Ames Research Center near San
07:51Francisco.
07:53Within this building is the Pioneer Mission Operations Center, headquarters for this as
07:57well as all previous Pioneer space missions.
08:11Instructions go out routinely in the modern hieroglyphics that border on English yet sound
08:15like gibberish to all but the controllers and their computers on the ground and in space.
08:27CMO, ACMO.
08:28CMO.
08:29Loaded and verified.
08:30Roger, thank you.
08:31Will you transfer to the enable queue?
08:34Roger.
08:40Nearing Venus and some 40 million miles from Earth, the two spacecraft listen to and heed
08:45their radio commands.
08:46The pace is deliberate yet precise to the microsecond.
08:54On November 16, the multiprobe turns to take aim at Venus then releases the sounder probe.
09:00All of the entry probes will maintain radio silence for nearly three weeks to conserve
09:05battery power.
09:06Will they switch on again properly?
09:08There's no guarantee.
09:10Four days later, the bus maneuvers again and loosens its grip on the three small probes.
09:18Orbit day, December 4, 1978.
09:25The controllers have done all they can.
09:28On the far side of Venus, an onboard computer must fire a retrorocket at precisely the right
09:33instant in the right direction for the right duration.
09:37It's known as a burn.
09:38Telemetry from the spacecraft continues to be normal with no indications of any difficulties
09:43with command memory.
09:45The FSI at 16.6.
09:47Coming up.
09:48We see no data yet.
09:55Timed for the convenience of Earthlings, the orbiter circles Venus once each 24 hours.
10:01Its low point deliberately dips into the very fringes of the atmosphere, while its long
10:06outer loop provides a vantage point for other instruments.
10:14Already science data is flowing, and soon the first picture is returned by an American
10:19Venus orbiter spacecraft.
10:21A crescent with not much detail, but it holds promise of more and better images to come.
10:36As the orbiter watches overhead, the calendar closes in on December 9.
10:41The clock counts down to the single hour during which the four entry probes will taste
10:46the Venus atmosphere, feel the heat and pressure, and chart the weather on this neighbor planet.
11:00After the weeks of silence, all ears strain for the first whisper from the four probes.
11:07We're waiting now for word.
11:15Roger that.
11:17Okay, we have it.
11:19We have the communications now.
11:22We can hear the transmitter from the sonar probe.
11:24We're right on time.
11:27The launch probe's on.
11:35Drawn in by the Venus gravity, the sounder probe disappears into the sulfuric acid clouds.
11:41Dante's Inferno straight ahead.
11:44Past the main entry heating level, the probe sheds its heat shield and deploys its parachute.
11:50Instruments sniff the clouds, then relay their data straight home.
11:56Even as the computers spew their first inscrutable numbers, the scientists sense new mysteries
12:01and choose their words with caution.
12:05Okay, that's mass 64. Don't say that's SO2.
12:08Don't speak of mass 64. Order 128.
12:14Well, everything's working great. They're all coming down now.
12:16The parachute worked, and I guess we've got about 30 more minutes of just drifting down very slowly.
12:21It's going to take 30 minutes to go through that soup up there, and it is soup.
12:24I think, I heard it's over 300 degrees already where we are.
12:27Centigrade.
12:28Pressures are going up.
12:31But everything's working just like it was planned.
12:35I don't know how we can ever anything greater.
12:39After 17 minutes beneath the parachute, the sounder releases and free falls
12:44through the ever thicker and hotter atmosphere.
12:47Next question.
12:48Will it survive the shock of landing and still send data?
12:52The probes weren't designed to, but it would be a nice bonus.
12:57Impact.
12:59Now they see the impact.
13:01They've seen the impact. They were a few seconds early.
13:10We lost it.
13:15Launch probe is gone. We have no more data coming in.
13:23Didn't survive.
13:27Now at five minute intervals, the three small probes impact Venus.
13:32Three more chances for a survival.
13:35And it happened.
13:38The daylight probe survived the appearance.
13:42There it is again. More.
13:44Now we're seeing the indication of good data coming in here.
13:47Three nights. Perfect data.
13:49Right.
13:50It was about 52.
13:5220 minutes. I'm predicting 20 minutes.
13:54Shut it off.
13:56It's phony data.
13:59Now the tension is reversed.
14:02Wagers on when the probe will die.
14:04Either crushed and cooked or starved for power.
14:08The interesting thing about this experiment being on the ground for an hour
14:14is that we had a chance to confirm the small amount of radiation.
14:18If we had one or two measurements, no one would trust them.
14:21But we got gobs of it, so now we can go back and see if we can really trust it.
14:25It's beautiful.
14:28Oblivious to the antics of the day probe,
14:30the bus now approaches its fiery rendezvous in the cloud tops.
14:34Two instruments gather data for one critical minute.
14:39Fourteens look like impact buds.
14:42And finally, 67 minutes and 37 seconds after the day probe landed on Venus...
14:49We've just confirmed the loss of signal from the day probe.
14:55You can imagine him sitting there seeing the temperature rise...
14:58Now the task of communications.
15:00Scientist to scientist. Scientist to public.
15:03There are major mysteries.
15:05Certain sensors on all probes failed or faltered at the same place.
15:09About 12 kilometers above the surface.
15:12Another instrument detected a strange glow,
15:15either from the spacecraft or the planet.
15:17Were both mysteries due to static electricity, St. Elmo's fire,
15:21or a chemical reaction of some unforeseen sort?
15:25We may never know.
15:26It's not condensable at any of the temperatures we see,
15:29and so there must be some rather potent chemical effect.
15:33Within the wealth of chemistry data on the Venusian atmosphere,
15:36some surprises, but the promise of understanding to come later.
15:40There's apparently very little water vapor today,
15:43which leaves the question open,
15:45did Venus ever have oceans, and if so, where did they go?
15:49And there was one chemical finding
15:51that may shake the foundations of traditional thinking.
15:54Perhaps the most outstanding result
15:57is the discovery that the atmosphere of Venus
16:00contains anywhere from 20 to 200 million tons of water.
16:0520 to 200 times as much neon, argon, and krypton
16:12as does the atmosphere of the Earth,
16:14whereas it contains just about the same amount of nitrogen and carbon dioxide.
16:20Now, we had expected,
16:22because these two planets have about the same size,
16:25about the same mass,
16:27that the amount of gas in their atmospheres would be the same.
16:32The fact that we haven't is going to force us to revise
16:36our theories of the origin of the planets
16:39and the origin of the solar system.
16:43Many instruments on the orbiter and the probes work together
16:46to study the so-called particles and fields of near-Venus space.
16:51The solar wind, the ionosphere, the upper atmosphere.
16:55Because Venus has no strong magnetic field to fend off charged particles,
17:00the ionosphere seems to be constantly changing and fluctuating
17:04in response to variations in the solar wind.
17:08Another instrument on the orbiter makes frequent pictures of the cloud tops.
17:12Viewed in ultraviolet light,
17:14curious dark markings come and go
17:17as they rotate around the planet approximately once in four Earth days.
17:25This series of images, taken over a two-week period,
17:28shows some of the recurring markings.
17:30Dark Y-shaped and bow-shaped features
17:33and bright high donut-shaped clouds surrounding the poles of Venus.
17:48Some of the most important new information comes from sensors on the probes
17:52as they sample conditions at points thousands of miles apart.
17:56They found changing, often violent, winds at different levels in the clouds.
18:00They found that most of the incoming heat from the sun
18:03is absorbed within the densest clouds,
18:05although a small amount reaches the surface.
18:11And they found that below the clouds, the air is free of dust particles,
18:15and the temperatures and pressures are virtually the same all over Venus.
18:27And they found a complex sulfur cycle instead of a water cycle.
18:32The clouds of Venus are made of sulfuric acid and possibly hydrochloric acid,
18:37literally, battery acid.
18:39It appears to rain out of the clouds
18:42and re-evaporate as it reaches the hotter regions below,
18:45a hail of fiery brimstone, literally.
18:49By coordinating data from all the probes,
18:52By coordinating data from all the probes,
18:55mapping of at least three major cloud decks around Venus is possible.
19:00One layer is described as being quite filthy,
19:03choking acid, smog-like conditions,
19:05filled with dust particles and debris.
19:07Sound familiar?
19:09The interaction of solar radiation with smog
19:12and how it affects our weather, of course, is important on Earth,
19:16and Venus is an excellent laboratory
19:19for studying these kind of smog-like conditions and its effect on weather.
19:24We're not supposing at this stage that Earth is starting in the direction of Venus
19:28to become completely dominated by these smog-like materials,
19:33but certainly man's activity on Earth
19:36is pushing us in the direction of more and more pollution.
19:40And we'll be able to tell quite accurately, I think, in the long run,
19:46through the study of Venus data, Pioneer Venus data in particular,
19:51the effects of this increasing pollution on our future climate and weather.
19:59On Earth, the problem of pollution has often been linked with the greenhouse effect.
20:04This trapping of incoming energy as heat
20:07was originally thought to explain completely the high temperatures on Venus.
20:12The data that we have at the present time do not entirely support the greenhouse model.
20:18There seems to be more infrared radiation leaking out of the atmosphere
20:21than there is solar heating coming in.
20:24So that forces us to go back and re-examine the other candidate explanation
20:29that has been available for a few years,
20:32namely the compression heating of the gases
20:37as they are carried down from the cloud levels
20:40or the higher levels of the atmosphere of Venus down to the surface.
20:45Now, the experimental data that we've acquired seem to offer another possibility,
20:50that the solar heat is absorbed in the clouds
20:53where measurements show that it is indeed absorbed
20:56and that it drives a vigorous circulation within the clouds.
20:59This circulation then causes the flow in the lower atmosphere
21:04to be dragged around frictionally by the principal driving cell,
21:09which is in the clouds.
21:10The polar region of the planet has a difference
21:15that sets it apart from the lower latitudes
21:19and that there appears to be a gathering of this circulation
21:24from the lower latitudes into a vortex.
21:26So we might say that there appears to be the equivalent of a hurricane
21:30sitting on the polar caps on Venus.
21:33The central portion of this is a region where the clouds are cleared
21:36because the infrared radiometer passing overhead in orbit
21:41is able to see higher temperatures
21:44by looking down through these holes in the polar cloud.
21:47This is what that infrared radiometer sees.
21:50The important features are the twin bright spots or hot spots near the center.
21:57This is the first time any spacecraft has looked down on the north pole of Venus.
22:02Apparently we are seeing into deeper, therefore warmer, layers of the atmosphere
22:07as the air over the poles rushes downward like water draining from a tub.
22:11This whole dumbbell-shaped hot spot rotates and wobbles around the Venus pole
22:16approximately every three days.
22:21A radar map around the orbiter charts elevation and types of terrain
22:25hidden beneath the clouds.
22:33This is a map of Venus made by ground-based radars
22:38and we're going to talk about three different areas
22:41that we've looked at with the Pioneer Venus spacecraft.
22:44This great northern feature, a region called Beta,
22:49and then an area near the Venus equator.
22:58The northern area was called the pear-shaped basin,
23:01when we got elevations from the Pioneer Venus spacecraft,
23:03it turned out to be a great plateau.
23:06Then there's a bright spot that's called Maxwell
23:09and it turned out to be a high mountain range.
23:12So this great plateau is uplifted more than a mile above the Venus surface
23:19and it has three great mountain ranges,
23:21one on the north, one on the west, and one on the east.
23:24This mountain range stands higher than Mount Everest does on the Earth.
23:29This great plateau is twice as big as the Tibetan plateau,
23:33which is the biggest one on Earth,
23:35and it stands more than 3,000 feet higher.
23:38So this is a planetary scale feature.
23:43Just west of there is what we think a great fault zone
23:47that breaks the crust of Venus and extends for something like 4,000 miles.
23:51It has two great volcanoes along it.
23:54We think they're volcanoes.
23:56They have about the right slopes
23:58and they stand more than a mile above the surrounding surface.
24:02We got a picture of the surface of Venus
24:05with the radar altimeter in the so-called imaging mode
24:09and we've been able to compare that image with the ground-based images
24:12and they match very closely.
24:14We'll keep going and get a strip like this all the way around the surface,
24:17whereas the ground-based radars can only see a short section.
24:21The most interesting thing about this picture
24:24are the round dark spots with little bright spots in the center.
24:28We've gotten altimeter traverses across them
24:31and they look like depressions,
24:33and that means they may be impact craters,
24:35and we have impact craters on the Moon, Mars, Mercury, and the Earth,
24:39and it looks like we have them on Venus also.
24:42The importance of the preservation of the impact craters
24:45is that on all the other planetary bodies,
24:48the big impacts took place in the far distant past.
24:51That would say that this is very ancient Venus crust.
24:55The great plateau and volcanic mountains and fractures of the Venus crust
25:01and the gravity anomalies all say
25:04that the Venus is a very active, dynamic planet.
25:08Maybe a little less, maybe a little more than the Earth.
25:11It's a little too early to tell you,
25:13but it does say that it's a very interesting place
25:15and we're looking forward to continued observations.
25:20To an artist, Venus looks like this.
25:23Craters, mountains, and volcanoes,
25:26the source of the sulfur that colors and pollutes the clouds.
25:29Virtually continuous lightning from unknown origins.
25:32Igneous rocks, basalts, and granites,
25:35probably involved in continental drifts that dwarf Earth's grandest features.
25:40Pressures like the bottom of an ocean.
25:42Temperatures to melt tin, lead, zinc.
25:46Are there lakes of gleaming alloys?
25:48Are there clouds of metal vapor?
25:50Where did the water go?
25:52Where did the argon come from?
25:54As always, the rule remains,
25:56for every answered question, a dozen more arise.
26:00Our universe is a curious place.
26:03Men of science and of far vision will persist,
26:07must persist,
26:09must understand.
26:19This is a photograph taken by the Soviet Venera 9 spacecraft
26:23in October of 1975.
26:25Another Venera lander made a chemical analysis of its landing site
26:30and found material resembling granite.
26:33The U.S. Pioneer Venus spacecraft,
26:36launched by the Lewis Atlas Centaur,
26:38orbited Venus.
26:40Radar was used to penetrate the thick clouds
26:43and give us images of the surface.
26:50The lower regions are blue.
26:52Yellows and reds show higher plateaus.
26:55Reaching as high as 11 miles above the blue parts
26:59is Ishtar Territory.
27:01Beta ratio has two extremely large volcanoes.
27:05Together, more extensive than the Hawaii-Midway volcanic chain on Earth.
27:13We have much still to learn about Venus.
27:16Is Venus, for example,
27:18at a stage which will eventually approach Earth-like conditions?
27:22Or is it geologically dead
27:24and unfathomable?
27:26This is Larry Ross saying goodbye
27:28from NASA's Lewis Research Center
27:30in Cleveland, Ohio.
27:32Next time, we will examine our home planet,
27:35Earth.
27:57NASA Jet Propulsion Laboratory
28:01California Institute of Technology
28:27NASA Jet Propulsion Laboratory
28:29California Institute of Technology