Viking 1 and 2

What were the Viking missions?

Viking was NASA’s first mission to land on Mars: two identical spacecraft, each an orbiterOrbiterAn orbiter circles Mars without landing, studying the planet from above — and many also relay rover data back to Earth.More in the glossary and a landerLanderA lander touches down on Mars and works from one spot, unlike a rover, which drives.More in the glossary that flew to Mars together.[1][6] Each pair weighed 3,527 kg (7,776 lb) at launch.[2] The orbiters ran on solar panels. Each lander carried two generators powered by the heat of decaying plutonium-238, so it didn’t depend on sunlight; NASA says that is what made their long missions possible.[1][2][8]

The two spacecraft swapped places before launch. The one meant to fly first had a battery problem, so its twin went first and became Viking 1.[2][3] NASA’s Langley Research Center managed the project with JPL.[2] NASA planned for 90 days of work after each landing. Every orbiter and lander lasted far longer.[1]

Each lander carried two cameras, a robot arm to scoop soil, a weather station, a small biology lab, an instrument to look for organic compounds and a seismometer.[2][8] Viking 1’s seismometer never unlocked, so the planned two-station marsquake network never happened.[13] Both seismometers were mounted on the landers themselves.[5] The first one set down on the ground arrived with InSight in 2018.[17]

Where did Viking 1 and 2 land?

Viking 1 landed in Chryse Planitia, and Viking 2 about 6,460 km (4,000 mi) away in Utopia Planitia, much farther north.[3][14] Both times, orbiter photos showed the planned site was rougher than expected, and NASA picked a new one.[2][3] That pushed Viking 1 past its target date, Jul 4, 1976, the US Bicentennial.[4] It came down about 28 km (17 mi) from its planned target.[2] For Viking 2, NASA picked a site nearer the north polar ice cap, where it said water was located and there was a better chance of finding signs of life.[3]

Dates in UTC. Coordinates from NASA’s Mars24 list of landers, in east longitude (312.05°E is 47.95°W). Other NASA pages put Viking 2 between 47.6°N and 48.0°N, and give some end dates a day or more apart (see below). Times on Mars are calculated from these dates.[1][2][3][7][10][14]

Was Viking the first landing on Mars?

It was the first fully successful one. The Soviet Union’s Mars 3 lander touched down on Dec 2, 1971, but stopped transmitting after about 14.5 seconds.[15] NASA describes Mars 3 as “a technical first with a survivable landing,” and Viking 1 as “the first truly successful landing on Mars.”[2]

Viking 1 touched down at 11:53 UTC on Jul 20, 1976, seven years to the day after Apollo 11 landed on the Moon. The radio signal confirming it took 19 minutes to cross about 341 million km (212 million mi) to Earth.[2][4]

What did the first photos from Mars show?

The ground under Viking 1’s own foot. The lander was programmed to take its first picture 25 seconds after touchdown, looking down at a footpad. It showed solid, slightly rocky ground, with dust and pebbles kicked up by the landing.[4][8] The next day, Jul 21, 1976, Viking 1 took the first color picture from the surface: orange-red soil over patches of darker rock.[4] It also took a 300-degree panorama of gently rolling plains.[2]

Viking 1 measured temperatures from −86 °C (−123 °F) before dawn to −33 °C (−27 °F) in the afternoon.[2] Viking 2’s landing was rougher. A radar misreading made its thrusters fire an extra time just before touchdown, and it settled with one leg on a rock, tilted about 8°.[3][10] Its pictures showed a flatter, rockier place than Viking 1’s.[3]

Did Viking find life on Mars?

No clear evidence of it. NASA says the landers’ three biology experiments “discovered unexpected and enigmatic chemical activity in the Martian soil, but provided no clear evidence for the presence of living microorganisms in soil near the landing sites.”[1][5]

Each lander scooped up soil with its robot arm (Viking 1 first did it on Jul 28, 1976) and fed it to three tests:[2][12]

• Labeled release added a nutrient broth tagged with radioactive carbon, then watched the air above it for radioactive gas, a sign of metabolism.
• Pyrolytic release looked for soil taking up carbon dioxide or carbon monoxide tagged with radioactive carbon, the way photosynthesis does.
• Gas exchange wet the soil with nutrients and measured gases such as oxygen, carbon dioxide and methane given off or taken up.

Some samples were heated to sterilize them and run again as controls.[12]

Viking 1’s results from four samples could have been read as a weak positive for life, NASA says. But the main test for organic compounds, a gas chromatograph mass spectrometer, came back negative.[2] The landers found no organic molecules at the parts-per-billion level, less than in Moon soil brought back by Apollo astronauts.[6] Viking 2’s experiments were just as inconclusive. Scientists believed ultraviolet radiation had created chemicals in the soil that could mimic signs of life.[3] NASA describes the soil at both sites as an iron-rich clay holding a highly oxidizing substance that releases oxygen when wet.[6][7]

The story has a later chapter. In 2008 NASA’s Phoenix lander found perchlorate in Martian soil, a chemical that destroys organic compounds when heated. A 2010 study suggested perchlorate was in Viking’s samples too. If so, the only two organic chemicals Viking detected, chlorine compounds blamed at the time on cleaning fluids from Earth, could have come from Martian organics destroyed as the samples were heated.[16] NASA scientist Chris McKay, a co-author, said the finding “doesn’t say anything about the question of whether or not life has existed on Mars.”[16] For where the search stands now, see Is there life on Mars?

What did the Viking orbiters see?

Almost the whole planet. The two orbiters returned 52,663 images and mapped about 97% of the surface at about 300 m (980 ft) resolution, NASA says.[2][3] They showed volcanoes, lava plains, immense canyons, landforms shaped by wind and evidence of surface water.[5][7] They also relayed the landers’ data to Earth.[9]

They came close to both moons in 1977. Viking Orbiter 1 made close passes of Phobos, and Viking Orbiter 2 flew within about 28 km (17 mi) of Deimos.[3][9][11]

What happened to the Viking landers?

Viking 2’s lander fell silent in 1980 when its batteries failed, and a bad command from Earth cut off Viking 1’s in 1982. The orbiters ran short of the gas they used to point themselves. In order:

1. July 1978 · Viking Orbiter 2A leak vented its attitude-control gas. NASA switched it off after 706 orbits and almost 16,000 images.[3][11]
2. Apr 11, 1980 · Viking Lander 2Its batteries failed, after about 1,280 solsSolA sol is a day on Mars — 24 h 39 min 35 s, about 40 minutes longer than ours — and rovers count them from the day they land.More in the glossary on the surface.[10][14]
3. August 1980 · Viking Orbiter 1Running low on attitude-control gas, it was raised into a higher orbit, chosen so it would not hit and possibly contaminate Mars before 2019. It was shut down after almost 1,500 orbits.[2][9]
4. Nov 11, 1982 · Viking Lander 1A faulty command sent from Earth cut communications. Attempts to regain contact failed. It had worked for more than six years.[1][2]

NASA’s own pages differ on some of these dates. Viking Orbiter 2’s end is given as Jul 7, 24 or 25, 1978, Viking Orbiter 1’s as Aug 7 or 17, 1980, and Viking Lander 2’s last day as Apr 11 or 12, 1980. Several NASA pages give Nov 13, 1982 as the end of Viking Lander 1’s mission.[1][2][3][7][9][11][14]

Mission timeline

1. Aug 20, 1975Viking 1 launches on a Titan IIIE-Centaur from Cape Canaveral.[2]
2. Sep 9, 1975Viking 2 launches.[3]
3. Jul 20, 1976Viking Lander 1 touches down in Chryse Planitia and sends the first picture from the surface.[4]
4. Jul 28, 1976Viking 1 scoops its first soil sample for the biology lab.[2]
5. Sep 3, 1976Viking Lander 2 touches down in Utopia Planitia.[3]
6. July 1978Viking Orbiter 2 is switched off after a leak.[3][11]
7. Apr 11, 1980Viking Lander 2’s last data reaches Earth.[1]
8. August 1980Viking Orbiter 1 is shut down, almost out of attitude-control gas.[2][9]
9. Nov 11, 1982Viking Lander 1 falls silent after a faulty command.[2]

Sources

1. NASA Science — Viking ProjectPrimary · checked Oct 6, 2026
2. NASA Science — Viking 1Primary · checked Oct 6, 2026
3. NASA Science — Viking 2Primary · checked Oct 6, 2026
4. NASA Science — Viking: 50 Years on MarsPrimary · checked Oct 6, 2026
5. NASA Science — Viking Spacecraft and SciencePrimary · checked Oct 6, 2026
6. NASA Science — Viking Project and AstrobiologyPrimary · checked Oct 6, 2026
7. NASA NSSDCA — Viking Project InformationPrimary · checked Oct 6, 2026
8. NASA NSSDCA — Viking 1 Lander (1975-075C)Primary · checked Oct 6, 2026
9. NASA NSSDCA — Viking 1 Orbiter (1975-075A)Primary · checked Oct 6, 2026
10. NASA NSSDCA — Viking 2 Lander (1975-083C)Primary · checked Oct 6, 2026
11. NASA NSSDCA — Viking 2 Orbiter (1975-083A)Primary · checked Oct 6, 2026
12. NASA NSSDCA — Viking 1 Lander: Biology (GEX/LR/PR)Primary · checked Oct 6, 2026
13. NASA NSSDCA — Viking 2 Lander: SeismologyPrimary · checked Oct 6, 2026
14. NASA GISS — Mars24 Sunclock — Mars LandersPrimary · checked Oct 6, 2026
15. NASA JPL — NASA Mars Orbiter Images May Show 1971 Soviet LanderPrimary · checked Oct 6, 2026
16. NASA JPL — Missing Piece Inspires New Look at Mars PuzzlePrimary · checked Oct 6, 2026
17. NASA JPL — NASA’s InSight Places First Instrument on MarsPrimary · checked Oct 6, 2026