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Fortieth anniversary of Viking invasion of Mars

by • July 19, 2016 • No Comments

Currently marks one of sizeablest moments in the history of space exploration, maybe 2nd only to the Apollo 11 landing that occurred on the same day in 1969. On July 20, 1976, the unmanned Viking 1 lander became the initially spacecraft to that good resultsfully land and operate on the surface of Mars. More than only a technological completement, this feat completely altered our view of the Red Planet in a way that kept upcoming planetary exploration of being seriously curtailed, and paved the way for an ambitious new generation of Mars undertakings.

  • Viking Lander flight configuration
  • Viking Lander bioshell
  • Viking 1 Lander prepped for flight
  • Viking 1 landing site seen by NASA's Mars Reconnaissance Orbiter

As the nuclear-powered Viking 1 touched down on the surface of Mars in 1976, there was a strange atmosphere of elation and pessimism back on planet Earth. The elation was understandable. Since 1960 there had been 24 undertakings launched by the United States and the Soviet Union to study Mars, but only four had been completely good resultsful. Now NASA had placed a working probe on the Martian surface intact, functional, and reporting back to planet Earth.

The pessimism was a thing additional new. The expectations of many scientists and participants of the public had been sat any timeely dampened in previous years and Mars was yett to be a dead planet.

Dead Mars

There’s a cliché question in talked of science that asks, “Are we alone?” In other words, is planet Earth the only inhabited planet in the universe? Could life exist elsewhere? Could it be in our own Solar System? These are inquiries that we yet ask, but the premises behind them are quite different types of at the present time than they were in 1976. In fact, the widely accepted answer preceding Viking 1 was, “Yes, we are alone. Very much so.”

Mars as seen by the Viking 1 Orbiter

The reason for this depressing sayment is that the previous 16 years had not been quite great for those seeking extraterrestrial life – so much so that the quite thing that was meant by “life” was essentially altered.

It wasn’t that many decades preceding the initially Sputnik that the yett of life existing or having once existed on Mars was taken quite seriously, but for a different types of definition of life than we harbor hopes of finding at the present time. When we talk of life on Mars in 2016, we mean microbes – a few sort of bacteria or virus, maybe remaining as nothing additional than fossils. Around 1900, life meant real live Martians assembling a planet-wide network of canals to bring water of the poles to irrigate farmlands and store their ancient, dying civilization alive.

This pretty romantic vision that inspired H.G. Wells and Edgar Rice Burroughs was tempered over time, and by 1960 the Martians of talked of imagination were replaced with the notion of a dead world that was a cross between the Gobi Desert and the top of Mount Everest. But “dead” meant a landscape where the air isn’t too thin and is dotted by scrub vegetation and a few primitive insect life. Even the many pessimistic scientist’s definition of “dead” allowed for a few mosses and lichens.

Best image of Mars returned by Mariner 4

Mosses and lichens? Anyone who found those on Mars at the present time may get an automatic Nobel Prize and a sizeable basket of fruit.

Two things killed this remarkably lively image of Mars. The initially was NASA’s Mariner 2 undertaking to Venus in 1962. If Mars had a rival for harboring life, it was eternally cloud-shrouded Venus, that equite sci-fi aficionado knew was a giant primeval swamp inhabited by dinosaurs. What Mariner 2 found instead was a planet with an atmosphere like a pressure cooker, temperatures high adequate to melt lead, and sulfuric acid rains for great measure.

Mariner 4

This odds rad was bad adequate, but and so on July 15, 1966, the Mariner 4 probe flew by Mars. As it did so, it sent back the most images yet of the Red Planet – a landscape pockmarked by craters and an atmosphere much thinner and drier than previously yett.

By the time Mariner 9 became the initially spacecraft to that good resultsfully orbit another planet in 1971 and mapped the surface of Mars in more detail, the verdict was all but sure. Mars was a quite, quite dead world with only the hope that the easyst of microorganisms can yet survive – yet no one was betting much on actually that outside of the quite optimistic few.

The Viking Program

NASA’s follow up to Mariner, the Viking program, began in 1968 and was tailored for three prime objectives:

  • To carry out a high-resolution orbital survey of Mars and return images of the surface

  • Study the chemical composition of the planet’s atmosphere and the surface

  • Look for evidence of life

To complete these goals, NASA created two identical spacecraft, so there may be a back up on Mars in the actuallyt of the other failing. Christened Viking 1 and Viking 2, at any timey probe consisted of a solar-powered orbiter and a nuclear-powered lander.


Acting as mothership for the lander, orbital survey craft, and communication relay with planet Earth, the Viking orbiter (PDF) was based on the good resultsful Mariner 9 create, yet with a adjusted engine, frame, and power process to accommodate the lander. The orbiter carried a pair of vidicon imaging cameras, an infrared spectrometer for water vapor mapping, and infrared radiometers for thermal mapping.

Propulsion for the orbiter was provided by a liquid-fueled rocket engine burning monomethylhydrazine and nitrogen tetroxide, that created 297 lb of thrust. Attitude control was courtesy of 12 nitrogen gas thrusters.

Power for the orbiter and for the lander on the way to Mars came of eight solar panels holding 34,800 solar cells that created 620 watts of electricity. Back up power for maneuvering and eclipses came of two nickel-cadmium 30-Ah batteries.


The late Carl Sagan compared the lander to either a grasshopper or an amoeba, depending on how you appeared at it. It was created of machined aluminum and titanium and shaped like a fat triangle with its points cut off and laid on its side.

Attached to this core were three landing legs that when extended gave the lander a width of 2.2 m (7 ft), but were in addition createed to fold up for the flight to Mars. The function of the legs was to absorb the impact of landing without jarring the delicate scientific instruments or avionics. As a outcome, the legs were a complex process of springs, shock absorbers, and crushable aluminum honeycombs. At the end of at any timey leg was a mushroom-shaped footpad, one of that may become world famous when it was the subject of the initially image of Mars.

All of the lander’s components had to be shielded not only against dust and radiation, but in addition against the extreme cold of the Martian night as well as the sat any timeal hundred degree fluctuations in temperature experienced on the voyage to Mars, and the high g forces and vibrations of lift off and landing. In addition, the lander had to practuallyt paint chips, metal filings, gases, or other bits of the spacecraft of escaping to contaminate the Martian environment.

The lander wasn’t only an instrument station. It was in addition a proper spacecraft with its own propulsion process for the last stage of the landing maneuver. This consisted of three liquid-fueled engines that throttled to up to 600 lb of thrust to slow the craft down for a relatively gentle landing. To practuallyt scorching the landing site, the engines had 18 nozzles to disperse the exhaust.

As to desktops, the landers utilized a Guidance, Control, and Sequencing Computer (GCSC) created of two Honeywell HDC 402 24-bit desktops with 18K of plated-wire memory. By at the present time’s standards, that may be like a modern Mars lander being run by the electronics of a one-dollar digital watch.

But the significant bits of the Viking 1 lander were its working tools. These consisted of a meteorology boom, an S-band low-gain antenna, a folding high-gain antenna dish, the robotic sampling arm, the laboratory module, and the cameras.

All of these were powered by two nuclear radiothermal generators (RTG). Each weighing 30 lb (13.6 kg), these were powered by plugs of plutonium and created 30 Watts of electricity at 4.4 volts. Between them, they may continually provide the lander with over 35 Watts of power to run the electronics and store the spacecraft of freezing at night. In addition, there were four nickel-cadmium batteries to assist with peak loads.

Unlike the orbiter, the lander needed special protection for the voyage to Mars. Because of the heat and stress of reentry, the lander needed to be sealed inside an aeroshell with an ablative heat shield. In addition, Viking 1 had to be protected against delivering any planet Earth microorganisms, so the spacecraft and its aeroshell were sealed in a bioshell and baked at 111° C (232° F) for 40 hours.

Mission to Mars

On August 20, 1975, Viking 1 lifted off of Cape Canaveral, Florida atop a Titan IIIE/Centaur rocket and arrived in Mars orbit on June 19, 1976. Since 1976 was the United States’ Bicentennial year, the original plan was for Viking 1 to land on July 4 – Independence Day. Unfortunately, for the reason the images of previous undertakings were of relatively low resolution and previously selected landing sites proved to be too rough, the orbiter had to carry out a new survey to find a suitable landing area and the landing date was put back.

On July 20 at 08:51 GMT, the lander, yet in its metal and plastic cocoon, separated of the orbiter. After the bioshell was jettisoned, the Lander executed a deorbit burn and plunged into the Martian atmosphere. Slowed by the heat shield, the spacecraft approached subsonic velocities in the thin air. At an altitude of 6 km (3.7 mi), the aeroshell blew away and the parachute deployed.

The lander descended to a height of 5,000 ft (1.5 km) when its descent engines kicked in and the parachute broke loose. Guided by radar, Viking 1 continued to descend for 40 2nds preceding, a short distance of the ground, the engines cutout and the spacecraft dropped in the ⅓ planet Earth gravity of the planet to land with a slight jolt.

The time was 11:53 GMT and the place was Chryse Planitia (22.48° N 49.97° W) near the Martian equator. Not wasting a moment, the lander’s desktop activated the onboard cameras. These two cone-like devices began to create up an image line by line like a high-definition color fax machine inside 25 2nds of touching down.

In four minutes, the initially image at any time seen unquestionably of Mars had been transmitted to planet Earth. It was a black and white picture (seen at the top of this article) of one of the lander’s footpads sitting on pebble-strewn ground. One other sactually minutes and a 300-degree panoramic scene of the terrain around the spacecraft arrived.

It wasn’t until the upcoming day that the initially color images were transmitted. At initially, these were rendered with a blue sky, but after calibrating the cameras with the test card mounted on the Lander, the true reddish haze of the Martian atmosphere was seen for the initially time.


But Viking 1 wasn’t on Mars only to send home holiday snaps. It had quite serious science to do. Next to nothing was understandn directly of the planet and there were adequate inquiries to begin with to fill sat any timeal lifetimes. Geology, chemistry, and actually biology needed to be addressed to fill in the quite sizeable blanks.

It wasn’t a quite auspicious begin. Viking 1’s initially failure was when the seismometer createed to study marsquakes jammed when the moving masses utilized to detect seismic waves was unlocked. Howat any time, the rest of the experiments went off much additional smoothly, with one key experiment being the meteorology boom that utilized three hot-film anemometers for measuring wind velocity, while another instrument measured ambient air temperature.

A significant component of the Viking Lander was its robotic arm. Unlike later articulated arms, this was a relatively easy device set on a rotating base. When deployed, the tubular metal arm telescoped out and a scoop may dig trenches and pick up soil samples. Once collected, the soil may be secured with a lid, and so conveyed to the hopper on the lander major to the created-in laboratory module.

Once inside, the samples were divided up for deliquite to different types of experiments, such as the X-ray fluorescence spectrometer (XRFS). This may take the soil and bombard it with X-rays of two radioisotopes, and so use counters to see how many fluorescent X-rays were emitted as a way to detect the different types of chemicals present.

The Search for Life

But the key question was whether life existed. In many ways, Mariner 4 was a blessing in disguise. Mars in 1976 seemed so hostile to life as we understand it that NASA had to appear much complexer for much less obvious signs. If primitive plants had been expected, there can have been additional emphasis on a visual survey. If the sort of microbes that are found in a terrestrial abandon were yett to be under the surface, and so a thing like standard Petri dishes and broth agars can have been utilized.

It’s the sort of search that may have quite rapidly found life on a additional planet Earth-like world, but on Mars it can have ended up like the classic mistake of the archaeologist who bored for soil samples at regular intervals over a site and missed an entire village for the reason he was digging between the houses.

Since any Martian life that can exist may have to do so in conditions that manufacture the Atacama Desert appear like the Amazon rainforest, NASA decided on a additional indirect approach that mayn’t appear for life, but for signs of biological activity created by that life. In other words, set up conditions for life and appear for evidence of feeding, excretion, and reproduction. The Viking lander carried three experiments to do only this.

Gas Exchange (GEX)

The initially of these was the Gas Exchange (GEX) experiment. In this, soil samples were immersed in a helium atmosphere and fed water and organic and inorganic nutrients. Over time, the atmosphere around the sample may be passed through a gas chromatograph for signs of carbon dioxide, oxygen, hydrogen, and methane.

Pyrolytic Release (PR)

The 2nd experiment was the Pyrolytic Release (PR). Soil samples were subjected to light and water in an atmosphere of carbon dioxide and carbon monoxide laced with radioactive carbon-14 (C-14). The yett was that if anything was carrying out photosynthesis, it may absorb the C-14. After a few days, the samples were moved to an oven and baked at 650° C (1,200° F) to release any absorbed carbon in the form of a gas and the C-14 may be measured by radiation counters.

Labeled Release (LR)

The third experiment was Labeled Release (LR), where the samples were fed a nutrient solution tagged with radioactive C-14. If there was anything eating the nutrient, it may create carbon dioxide or a few other byproduct, that may contain traces of C-14, that may be measured.

Was Life Found?

At initially, the Viking experiments seemed to confirm that Mars was as dead as disco. The gas chromatograph and soil studies found no traces of organic molecules. Worse, the GEX and PR experiments were completely negative.

First color image of the Martian surface

Howat any time, the LR experiment gave a few hope – at initially. In the initially test run, radioactive C-14 was given off shortly after the nutrient solution was added and this held true for samples taken of at a lower place the surface as well as those scraped of on top. This was promising, but when the experiment was rerun on the same samples a week later, nothing happened. The same held true for the third try.

If a thing had been alive, it may have accounted for the gas release, but if it was alive, it should have kept operating as additional food was added. Instead, the reaction stopped and mayn’t rebegin. With no organic molecules and a begin/stop cycle, if this was life, it wasn’t like anything seen preceding.

What was taking place in the Viking experiments is yet controversial, but the current consensus is that what the lander found wasn’t strange life, but strange chemistry.

Frost on Mars

Living on planet Earth, we tend to forget that water isn’t as bland a liquid as we ponder. According to chemists, it is actually one of the many reactive substances and of as close to a universal substance as is possible. It permeates so much of our terrestrial environment that it is actually completely altered the planet’s chemistry and created many compounds as rare as acorns at a squirrel convention.

On Mars, the surface is drier than any place on planet Earth, the air is a near-vacuum, and there’s no magnetic field. The outcome is that the surface is constantly bombarded by complex ultraviolet radiation and cosmic rays. This produces all sorts of sturdy oxidizing molecules that on planet Earth may soon be destroyed on contact with water. On Mars, such molecules are common and such compounds are incredibly destructive to organic molecules.

In 2008, NASA’s Phoenix lander found that there are perchlorates in the Martian soil. One theory is that these highly-oxidizing salts interacted with the nutrient solutions and created the lifelike outcomes. This may in addition explain why the reactions ceased when the perchlorates were utilized up. Howat any time, the Viking experiments are regarded as inconclusive as to whether anything living was encountered.

Viking 2

As “Viking 1” implies, there was a Viking 2 undertaking. The 1970s were yet the quite early days of Mars exploration and the high failure rate meant that additional than one spacecraft may be sent to do the same job as insurance. Identical to the initially craft, Viking 2 separated of its orbiter and landed on a sizeable plain called Utopia Planitia (Latin for “Nowhere Plain”) on September 2, 1976. Its undertaking was the same as Viking 1 and it carried out the same life experiments with the same outcomes.

Viking 2 landing site

Similar to Viking 1, Viking 2 was createed to operate for of 90 days, but it continued to function for far longer, holding out for 1,316 days preceding its batteries failed on April 11, 1980. The Viking 2 orbiter failed on July 25, 1978. Meanwhile, the Viking 1 orbiter lasted until August 17, 1980 and the lander, now called the Thomas Mutch Memorial Station in honor of the leader of the Viking imaging team, went offline on November 13, 1982 after 2,307 days when a software update accidentally cautilized its high-gain antenna to point away of planet Earth.

A New View of Mars

The Viking undertakings may have remained in one spot on the Martian surface, but they essentially changed our perceptions of Mars. They didn’t find iron-clad proof of life, but the lander experiments sparked new interest and put the search for present or past life on the Red Planet at the top of NASA’s planetary sciences’ to-do list.

In addition, the images sent of the landers and the orbiters showed that Mars wasn’t always a dead ball of dust. There were indications that vast areas of permafrost may exist under the sandy abandons and the rough highlands and the terrain showed definite signs that ancient floods had carved deep valleys and flooded plains. There were in addition what appeared like dried streambeds and the slopes of the Martian volcanoes appeared as if they’d been carved by rainfall and water-based chemical erosion.

There were actually signs that the Martian climate ran in cycles with underground volcanoes melting ice to cause floods, only to freeze again.

Later Missions

Viking 1 was not only the initially functioning lander on Mars, but it held the record for longest operation on the planet until the Opportunity rover overtook it on May 19, 2010. Howat any time, the Viking program was additional than a trailblazer, its findings had a significant impact on later undertakings.

Pathfinder Sojourner rover

There mayn’t be another Mars landing until NASA’s Mars Pathfinder undertaking touched down in 1997. This was additional of a demonstrator undertaking than anything else and was meant to show that a Mars undertaking may be staged for a 15th of the cost of Viking. Consequently, it is actually experiment box was easyr than Viking’s, but the inclusion of the Sojourner rover was based in part on Viking’s discoquite of the diversity of the Martian landscape and the necessity of going where the data is..

The upcoming two lander attempts were failures. In 1999, NASA’s Mars Polar Lander, createed to study the high latitudes of the planet, lost contact while descending in the direction of the south pole of Mars. In 2003, ESA’s Beagle 2 lander in addition lost contact when its solar panels failed to deploy.

Artist’s concept of the Opportunity rover

This losing streak was broken by NASA’s Mars Exploration Rover program, that set down the Spirit and Opportunity rovers on Mars in 2003 and 2004 respectively. These undertakings reflected the new philosophy that the most way to decide the question of life on Mars is to learn additional of the geology and history of the planet. The yett is that by learning additional of the nature of Mars can allow the proper question to be posed when it becomes time once again to appear for life.

Howat any time, it wasn’t until Curiosity begined to roll across the Martian hills in 2012 that the question of life again became a specific goal. The nuclear-powered probe wasn’t createed to appear directly for life, nor for signs of it like Viking. Instead, it was and is appearing for specific areas where life may have survived. Toward that end, it has been seeking out clay formations, ancient stream beds, areas of floods of billions of years ago when Mars was much wetter, and minerals that may only be created in the presence of water.

The Future

All of this work over the past two and additional decades may have been not easy without Viking. It lifted the veil what was believed to be a dead, nat any time-been-born planet that was little additional than a cosmic artillery range and begined science on a path of new belief. It became a world that was once again worth serious study, one that we now understand to be quite different types of in the past, with a surface showcasing oceans, lakes, and rivers.

At the moment, there are sactually undertakings operating on and around Mars, with additional on the way. This upcoming generation of Mars exploration won’t only be say sponsored, but can include the initially privately funded undertakings via privately created spacecraft. It’s a generation that is seriously thinking not only the initially manned undertaking to the Red Planet, but actually colonization with permanent settlements where only robots roam at the present time.

It was the good results of Viking that created it all possible. By carrying out not one, but two landings on Mars, lessons were learned that now manufacture multiple-probe deep space undertakings a thing of the past, while the data sent back turned Mars into a understandn, well-mapped world that real inquiries may be asked of. But many of all, it is ironic that Viking’s initially search for life has ushered in a time when the answer to the question of whether there is life on Mars can be “yes” – actually if that life turns out to have been born on planet Earth.

  • Viking 1 back shell seen by NASA's Mars Reconnaissance Orbiter
  • Viking 1 back shell seen by NASA's Mars Reconnaissance Orbiter (close up)
  • Viking 1 heat shield seen by NASA's Mars Reconnaissance Orbiter
  • Viking 1 Lander seen by NASA's Mars Reconnaissance Orbiter

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