Unraveling Venus

Whenever anyone gets me talking about space and spaceflight, they invariably ask what got me started on ‘all of this space stuff’ in the first place. The short answer is Venus. I became captivated by the planet researching a second grade science project and my interest has continued growing from there. It is a planet, sometimes referred to as Earth’s twin but really more like the Earth turned inside out, that and I can see in the sky! But it’s never been the object that truly captivates me; it’s the hunt to learn about the object.

When I researched that first project, I found the bulk of the information I needed quickly. Growing up in the age of computers I had encyclopaedic information available at my fingertips. I quickly learned that Venus has no moons, that it rotates in the opposite direction than Earth, that it is an extremely hot place, and that lightening storms continuously rip through the planet’s thick atmosphere. The descriptions were accompanied by fantastic images that perfectly matched the excitement of such an alien world. Images such as:

I also found an actual image of the surface of Venus. Compared to the depictions of lightening against the yellow clouds (that I learned were so coloured due to the carbon dioxide in the atmosphere), true images were, well, unexciting:

Venus, I was surprised to find, looked like the view I got when I lay on the beach on my stomach and looked up with my eyes. I was determined to find an image of the planet that captured the excitement of its properties. I found, however, that no such image exists – as I would soon learn, photographing Venus is exceedingly difficult. And so I changed tactics. I sought to learn as much about the planet and the existing photographs to contextualize the information I already had.

I quickly found that digging through history to piece together a background to the human exploration of the planet was far more interesting than the compiled facts that had initially captured my imagination.

As the brightest object in the sky aside from the Sun and the Moon, Venus has long been an object of interest for astronomers. Its nomenclature reflects the peaceful beauty of the brightest celestial wanderer; it is named for the Roman Goddess of beauty. Other classical names are equally complimentary. To the Greeks, Venus was known as Aphrodite, the Goddess of Love, and to the Babylonians as Ishtar, the Goddess of Love and Fertility. (Above, Venus on the horizon as seen from orbit. STS-30, 1989.)

For centuries, the Aristotelean/Ptolomaic geocentric order of the universedominated astronomy. It was, after all, completely absurd to assume that we humans were not the centre of the universe. Venus was one of six bodies wandering around the Earth in the sky. The Sun, the Moon, Mercury, Mars, Saturn, and Jupiter were its wandering companions. (The geocentric model, in order: the Moon, Mercury, Venus, the Sun, Mars, Jupiter, Saturn.)

In the mid 16th, Polish astronomer Nicolaus Copernicus (pictured, with heliocentric model) radically changed the solar system. In an attempt to explain the retrograde motion of Mars (it appears to periodically move backwards in its orbit), he decentred Earth and proposed the heliocentric model of the solar system.

This wasn’t an easy change to accept. Danish astronomer Tycho Brahe attempted to salvage Earth’s centrality with a geohelioctenic model (pictured): the Earth orbits the Sun, but all the other known planets continued to orbit the Earth. A messy solution (and one of my favourites!).

In the 17th century, Venus played a vital role in confirming Copernicus’ heliocentric theory. Italian astronomer Galileo Galilei was one of the first to apply the new technology of the telescope to the study of the heavens. In addition to his observations of the Moon and discovery of Jupiter’s four largest satellites, Galileo took detailed observation of the phases of Venus. Venus, he found, has the same phase cycle as our moon. This gave concrete support to the heliocentric model; it was the only explanation for Venus’ apparent waxing and waning.

Galileo's drawings of the phases of Venus

In the late-18th century, Venus again united the astronomic (and general scientific) community. 1761 and 1769 marked two transits of Venus. A rare view of Venus crossing the disk of the Sun, transits come in pairs about once each century. Both Rev. James Gregory and Sir Edmund Halley independently proposed the same method that would use the transit of Venus to determine the distance from the Earth to the Sun, or one Astronomical Unit: measuring the parallax shifts as Venus moves.

This 18th century pair of transits led to another important astronomical discovery. While attempting to measure Venus’ diameter during its passage in front of the sun, Russian astronomer Mikhail Vasilievich Lomonosov was puzzled by an odd fuzziness surrounding the planet. He expected to see a flat disk. The only explanation that fit with his observations was that Venus had a visible atmosphere. (Pictured are three modern images of Venus passing in front of the Sun. 2004.)

In the 19th century, theories of pluralism became central in astronomy – the idea that life can exist on other planets. One of the strongest factors supporting theories of extraterrestrial life was the gradual acceptance of Darwin’s theory of evolution. He had proved that organisms grow and develop into increasingly complex (and in some cases intelligent) life forms. If it happened on Earth, there was no reason to assume it couldn’t or hadn’t happen elsewhere.

The increasing knowledge of geology on Earth was also inciting the beginnings of comparative planetology. Phenomena observed on Earth were widely applied to other planets. Venus quickly became a hotspot for assumed extraterrestrial life, perhaps in holding with the warm and peaceful notions presumed by its nomenclature and certainly influenced by Lomonosov’s discovery of a Venusian atmosphere.

One of the strongest supporters in the theory of a plurality of was the Scottish astronomer William Brewster. He publicly sparred with known anti-pluralist William Whewell, bringing the question of extraterrestrial life into the general scientific sphere.

Brewster argued in favour of life on Venus on the strength of its apparent similarity to Earth: both planets have an atmosphere, as well as near 24-hour long daily rotation and regular seasons. Observations of Venus from Earth also revealed an apparently variegated surface, suggesting a geologically active planet. Venus is slightly denser than Earth, but it’s smaller size balances out the pull of gravity, and so the gravity felt on Venus is the same as is felt on Earth. Most of Brewster’s arguments concluded with the explanation that God wouldn’t create a whole universe without life. That was too wasteful to be divine!

A comparison of the terrestrial planets (to scale). The similar sizes of Earth and Venus are apparent. The surface detail on Venus is a composite of radar images taken by the Magellan spacecraft.

Other astronomers took a less definitive stance. British astronomer Richard Proctor, best known for his early efforts to map Mars, was less certain that life existed on every planet. He conceded, however, that if life were to exist elsewhere in the solar system, Venus was the likeliest candidate for a life-harbouring planet.

Another theory en vogue in the 19th century was the nebular hypothesis. First articulated by French mathematician Pierre-Simon Laplace, the nebular hypothesis posited that the matter in the solar system is cooler the further it is from the Sun. He explained the genesis of planets as the condensing of matter in specific regions or ‘circles’ of the solar system. This is how the planets came to be in their specific orbits around the Sun.

According to the nebular hypothesis, the planets closest to the sun are warmer than those further, and each planet is in a different stage of cooling. The further a planet is from the sun, the colder and more dead it is, and they would all end up equally cold and dead in the long run.

Earth is in its peak stage; neither too hot nor too cold, it is just right for harbouring life. But it is cooling and dying. If Venus didn’t harbour life, it is because the planet is less developed. It is not quite cooled to the point of harbouring life, but it is on its way. Mars, the next furthest planet from the Sun was assumed to be a dead world, the future of Earth once it aged a little more.

In the early 20th century, opinions of Venus as the gentle and beautiful Goddess of the sky or the tropical young world quickly fell out of favour as increasingly sophisticated technology was applied to astronomy. In the 1920s, spectroscopy shattered previous notions of Venus. Spectroscopic observations – measuring the absorption spectrum of light to determine the chemical composition of a body – revealed Venus as a world shrouded clouds not of water vapour like on Earth but of carbon dioxide. In the 1950s, radio observations of Venus revealed intense microwave radiation around the planet, an indication that its surface was not temperate but unbearably hot. Venus was beginning to look like a truly inhospitable environment. (A spectroscopic image of Venus (pictured) shows the varying levels of clouds surrounding the planet.)

The dawn of the space age brought new possibilities for discovering the mysteries of Venus. Sending a spacecraft to the planet would reveal more than could be gathered from Earth-based observation. To this end, the leading powers in space – the Americans and the Soviets – were not only fighting to land a man on the moon, they were engaged in a race to Mars and Venus as well.

The first probe to visit Venus was the American Mariner 2 (pictured), launched in 1962. The mission was a success; it flew within 21,000 miles of the planet and sent valuable data back to Earth. Of particular importance was the onboard microwave radiometer, which determined the surface temperature of Venus to be about 500 degrees centigrade.

After Mariner 2’s initial success, the Americans focussed their efforts on landing a man on the moon and reaching the surface of Mars. This left the bulk of Venusian exploration to the Soviets. In the early 1970s, the Soviet Space Program (under the urging of Roald Sagdeev, the director of the Soviet Space Research Centre) focussed its efforts on a new goal: it wanted to be the first nation to ever return an image from the surface of another planet. A successful mission would give the Soviets a major accomplishment over the Americans.

The Soviets had begun a program to send probes to Venus in the early 1960s: the Venera program. Missions had reached the planet and landed on its surface, but none were equipped to photograph the landscape. The new program goal meant that the Venera spacecraft had to be redesigned to optimize its chances of success.

Of particular importance to a successful mission was the transit time from Earth to Venus. Because repairs to a spacecraft in transit are difficult at best, the instrumentation had to be as solidly made as possible. Shortening the time the spacecraft would spend in transit would lessen the opportunities for the instrumentation to fail. The life span of the lander was only expected to be 30 minutes on the planet’s surface. Keeping it as healthy as possible until landing was essential.

The first mission to attempt a photographic return from the surface of Venus was Venera 9, also one of the redesigned Venera spacecraft.

The spacecraft consisted of two parts, an orbiter and a lander. The lander was cylindrical with a flared bottom covering the engine. The bulk of the instrumentation was on the top half of the lander with two large solar panels for power. Among the onboard instruments were a thermometer, accelerometer, barometer, and mass spectrometer. All told, the lander was a little over 9 feet tall and weighed about 11,100 pounds – about 3,500 pounds for the entry probe (pieces of which be jettisoned during descent) and about 1,455 pounds for the lander.

The prize instruments on board Venera 9 were the cameras. The lander had two cameras placed on opposite sides from one another below the airbrake. Each could take a 180-degree panorama; both shots together would be a complete view around the lander.

This cameras’ position was a compromise. There were two options: they could be placed either above or below the airbrake, which sat about halfway up the lander. The decision was made to place them below the air brake, which meant that they would only be able to view the surface from very low angle; the design was too simple to allow any manipulation of the camera once the craft landed. A view of the horizon would be impossible.  This wonky view, however, was better than the alternative. If the cameras had been placed above the airbrake, the prized view of the surface would be obscured almost entirely by pieces of the lander.

The Soviet Union launched Venera 9 in June of 1975. Four months later, its orbiter became the first spacecraft to enter into a permanent orbit around another planet. The lander separated from the orbital probe and began its decent to the unknown surface of the planet at over 6.2 miles per second, relaying information about the Venusian atmosphere the whole time.

The lander (pictured) was designed to use the thick atmosphere to its advantage. The flared bottom half had panels shielding the engine that also acted like an air brake against the thickening atmosphere. About 40 miles from the surface, three drogue chutes deployed, releasing a small metallic parachute to slow the lander’s fall to a more comfortable 820 feet per second. 31 miles from the surface, the parachute was jettisoned leaving the bulk of the work to the disk brake. In the final stage of the descent, a compressible, metal, doughnut-shaped, landing cushion deployed to enabled a soft landing on the surface. The final touchdown was assisted by shock absorbers.

Venera 9 touched down at just before 8:30 in the morning Soviet time on October 22. Transmissions from the surface began immediately, the cameras springing to life without hesitation since a photograph was the ultimate goal. The protective covers dropped to reveal the lenses, protected from the crushing atmosphere by 1cm thick quartz windows. A light meter measured the reflectivity of the surface to determine whether or not a naturally lit photograph would be possible. In the event of a dark landing spot, Venera 9 carried a 10,000 lux floodlight to illuminate the area around the lander for the prolonged exposure shot. It wasn’t necessary; the sunlight was favourable enough to show the surface features in their natural illumination. (Pictured: a Soviet engineer moves to inspect a Venera lander after a landing test.)

To return a high quality image, the camera recorded data in lines that would be reassembled on Earth into a composite single image. In total, the complete image consisted of 517 individual lines of image data, a substantial amount of information. The data took an hour to reach Earth, but was eventually reassembled into a complete view of the Venusian surface, the first image taken form the surface of another world.

Unfortunately, one of the two cameras malfunctioned. Instead of the hoped for 360-degree panorama, scientists only saw what was on one side of the lander. Disappointment at the technical malfunction was quickly quelled by the information within the image.  The Soviet scientists were astounded. They had been expecting a straight view of the immediate foreground. But it turned out that Venera 9 landed on a young mountain. The view looking down from a slightly raised angle gave the image much more detail and depth. The horizon could actually be seen roughly 300 metres in the distance.

Temperatures inside the Venera 9 lander rose steadily from the moment it reached the surface. Finally, when the internal temperature reached 60 degrees Celsius, the lander stopped transmission to Earth. It had lasted for 53 minutes of the surface of Venus.

The same first image of the surface of Venus from Venera 9. This image has been processed to balance brightness and tones according to other data returned by the lander.

I was fascinated with Venus when I first read about its principle differences from Earth. Having looking through its history to gain a complete context for our current knowledge, knowing the various incarnations Venus has enjoyed throughout our history, I am more impressed at the lengths astronomers have taken to learn as much as they have.

But it is studying the technology of how that one image was taken that truly astounds me. Looking at the image without context, it is impossible to fathom how difficult it is to take a picture from the surface of another world (unless you’re an astronomer, in which case this is probably something that seems so obvious to you). Tracing even a rough history of the events leading up to a single photograph present a startling picture. Behind that single image is years of planning and developing specialized spacecrafts and instruments. It is hard not to be astounded, with the context fresh in my mind, at that same image that once seemed too normal to be alien.

This is why I study the history of space science and spaceflight.

Suggested Reading/Selected Sources

Brian Harvey. Russian Planetary Exploration. Springer Praxis. 2007.

Richard Corfield. Lives of the Planets. Basic Books. 2007

Mike Brown. How I Killed Pluto and Why it Had it Coming. Spiegel & Grau. 2010.

“Venera 9 Lander Mission Page”.  http://nssdc.gsfc.nasa.gov/imgcat/html/mission_page/VN_Venera_9_Lander_page1.html

Comments

  1. says

    Amy:

    I was on hand for the STS-30 launch in 1989. At the time I lived in Orlando. I got ASTRONOMY magazine to get me credentialed after I visited with Magellan in a cleanroom during the STS-29 mission (which I covered for SPACEFLIGHT). Magellan was the first robotic mission to leave the U.S. for 11 years, and the public response was surprisingly enthusiastic. ASTRONOMY hadn’t figured on getting much from me – maybe a little news piece – but they asked for a feature after they saw signs in Milwaukee (where they are based) that said things like “Go STS-30! America returns to Venus.” That was really cool – planetary science people at that time were feeling pretty put down since they’d had to become dependent on the Shuttle and had had no new launches for so long. Magellan meant the end of the drought, and it wasn’t only planetary scientists that noticed.
    – DSFP

  2. says

    How do you feel about the possibility of Venus as a habitable planet for life? Certainly the surface of the planet is far too hot for life as we know it to survive, but what about in the atmosphere? A 2003 report by NASA’s astrobiology Institute suggests that “Above the cloud layers, the atmosphere of Venus is remarkably earthlike (although lacking free oxygen)… the atmospheric pressure is one bar, equal to the pressure of Earth’s surface, at an altitude of about fifty kilometers above the surface. At the altitude where the pressure is about one bar, the temperature is about 350 K; decreasing to 263 Kat an altitude of 60 km above the surface. While the surface is perpetually cloud covered, at approximately the one bar level, considerable sunlight is available. The atmospheric composition is primarily carbon dioxide and nitrogen; the cloud aerosol particles are primarily sulfuric acid (H2SO4) droplets.” (2.1 The Suitability of the Venus Environment for Life)

    The article goes on to suggest that “There is some evidence that the trace-gas constituents of the Venus atmosphere are not in chemical equilibrium with each other.” (3.3 Present Life) And while that doesn’t necessarily indicate biology is present, it does at least warrant more research to figure out what is causing this weird disequilibrium.

    Anyway, I was just wondering if you had heard about this argument and if you had any opinions on the subject. Thanks.

    http://gltrs.grc.nasa.gov/reports/2003/TM-2003-212310.pdf

    • says

      I hadn’t heard of this, but it’s fascinating. Thanks for including the link to the paper – a little after the fact, possibly, but I might be dealing with Venus again very soon!

  3. says

    Actually some NASA people came up with the idea of a habitat in orbit above the clouds as a livable option once arriving at Venus.
    It would present a more complete picture if we could resolve the question of our strange planetary make-up as compared to the findings of Kepler.
    The simplest explanation may be that Sol had a twin whom I call Pal, it exploded, its remanents are the Ort cloud. The magnetic field NASA calls Fluff is still here, the ‘smoking gun’ as it were.
    We have no end of theories involving comets, unseen planets, solar flares, and cosmic energy. I am interested in the cosmic energy input which may have energized Fluff to such an extent that its expansion ‘squeezed’ Sol’s heliosphere, forcing it to retract but since Sol’s realm is mostly gas, it just compressed. This is what you see when you look at the catastrophic result of compression and release. The action of realignment of crystal axes by expansion (pyroelectric) and contraction (pizeoelectric) both produce electricity when realigning. As Fluff surges over the once Sol-ruled planets, pyroelectric expansion would occur. Note the gas giants. As the magnetic surge continues what is left of Sol’s realm endures greater compression. Gases compress, axes of crystal realign releasing pizeoelectrity. Science tells us that higher than 21% oxygen would allow carbon material to ignite spontaneously. Suppose that happened to Mars. We had almost that high an oxygen content during dino days. Earth suffered two separate expansion events as documented by S W Carey, 50 my apart.

    The Voyagers I & II discovered high energy in Fluff. The claim is made we are passing thru. In as much as the human race is only ( as far as we can document) 5 myo, and we have been in Fluff for 10 how is that relevant? Except to give us hope that this too shall pass. More likely we too shall pass.

Trackbacks

Leave a Reply