Viking 1 was the first of two spacecraft sent to Mars as part of NASA's Viking program, and holds the record for the longest Mars surface mission of 6 years and 116 days (from landing until surface mission termination, Earth time).
The landing rockets used an 18 nozzle design to spread the hydrogen and nitrogen exhaust over a large area. NASA calculated that this approach would mean that the surface would not be heated by more than one degree Celsius, and that it would move no more than 1mm of surface material. Since most of Viking's experiments focused on the surface material a more straightforward design would not have served.
The Viking 1 Lander touched down in western Chryse Planitia ("Golden Plain") at 22.697° N latitude and 48.222° W longitude at a reference altitude of −2.69 km relative to a reference ellipsoid with an equatorial radius of 3397.2 km and a flatness of 0.0105 (22.480° N, 47.967° W planetographic) at 11:53:06 UT (16:13 local Mars time). Approximately 22 kg of propellants were left at landing.
Transmission of the first surface image began 25 seconds after landing and took about 4 minutes. During these minutes the lander activated itself. It erected a high-gain antenna pointed toward Earth for direct communication and deployed a meteorology boom mounted with sensors. In the next 7 minutes the second picture of the 300° panoramic scene (displayed below) was taken. On the day after the landing the first color picture of the surface of Mars was taken. The seismometer failed to uncage, and a sampler arm locking pin was stuck and took 5 days to shake out. Otherwise, all experiments functioned nominally. The lander had two means of returning data to earth: a relay link up to the orbiter and back, and by using a direct link to earth. The data capacity of the relay link was about 10 times higher than the direct link.
The lander had two facsimile cameras, three analyses for metabolism, growth or photosyntheses, a gas chromatograph-mass spectrometer (GCMS), an x-ray fluorescence spectrometer, pressure, temperature and wind velocity sensors, a three-axis seismometer, a magnet on a sampler observed by the cameras, and various engineering sensors.
The Viking 1 Lander was named the Thomas Mutch Memorial Station in January 1982 in honor of the leader of the Viking imaging team. The lander operated for 2245 sols (about 2306 earth days or 6 years) until November 11 1982, when a faulty command sent by ground control resulted in loss of contact. The command was intended to uplink new battery charging software to improve the lander's deteriorating battery capacity, but it inadvertently overwrote data used by the antenna pointing software. Attempts to contact the lander during the next four months, based on the presumed antenna position, were unsuccessful. In 2006 the Viking 1 lander was imaged on the Martian surface by the Mars Reconnaissance Orbiter.
Gravitational time dilation is a phenomenon predicted by the theory of General Relativity whereby time passes differently in regions of different gravitational potential. Scientists used the lander to test this hypothesis, by sending radio signals to the lander on Mars, and instructing the lander to send back signals. Scientists then found that the observed signals matched the predictions of the theory of General Relativity.