Viking 1
Encyclopedia
Viking 1 was the first of two spacecraft sent to Mars
as part of NASA
's Viking program
. It was the first spacecraft to successfully land on Mars and perform its mission, and until May 19, 2010 held the record for the second longest Mars surface mission of 6 years and 116 days (from landing until surface mission termination, Earth time).
/Centaur
launch vehicle on August 20, 1975 and a 10-month cruise to Mars, the orbiter began returning global images of Mars about 5 days before orbit insertion. The Viking 1 Orbiter was inserted into Mars orbit on June 19, 1976 and trimmed to a 1513 x 33,000 km, 24.66 h site certification orbit on June 21. Landing on Mars was planned for July 4, 1976, the United States Bicentennial
, but imaging of the primary landing site showed it was too rough for a safe landing. The landing was delayed until a safer site was found. The lander separated from the orbiter on July 20 08:51 UTC and landed at 11:53:06 UTC. It was the first attempt by the United States at landing on Mars.
consisted of two vidicon cameras for imaging (VIS), an infrared spectrometer for water vapor mapping (MAWD) and infrared radiometers for thermal mapping (IRTM). The orbiter
primary mission ended at the beginning of solar conjunction
on November 5, 1976. The extended mission commenced on December 14, 1976 after solar conjunction. Operations included close approaches to Phobos
in February 1977. The periapsis
was reduced to 300 km on March 11, 1977. Minor orbit adjustments were done occasionally over the course of the mission, primarily to change the walk rate — the rate at which the areocentric longitude changed with each orbit, and the periapsis was raised to 357 km on July 20, 1979. On August 7, 1980 Viking 1 Orbiter was running low on altitude control gas and its orbit was raised from 357 × 33943 km to 320 × 56000 km to prevent impact with Mars and possible contamination until the year 2019. Operations were terminated on August 17, 1980 after 1485 orbits.
slowed the craft as it plunged through the atmosphere. During this time, entry science experiments were performed by using a retarding potential analyzer, a mass spectrometer, and pressure, temperature and density sensors. At 6 km altitude, traveling at about 250 m/s, the 16 m diameter lander parachutes deployed. Seven seconds later the aeroshell was jettisoned, and 8 seconds after that the three lander legs were extended. In 45 seconds the parachute
had slowed the lander to 60 m/s. At 1.5 km altitude, retrorockets on the lander itself were ignited and, 40 seconds later at about 2.4 m/s, the lander arrived on Mars with a relatively light jolt. The legs had honeycomb aluminum shock absorbers to soften the landing.
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 48.222°W 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. This first color image has since been lost or misplaced. Additionally, 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
.
s. The tested soil contained abundant silicon
and iron
, along with significant amounts of magnesium
, aluminum, sulfur
, calcium
, and titanium
. Trace elements, strontium
and yttrium
, were detected. The amount of potassium
was one fifth the average for the Earth's crust. Some chemicals in the soil contained sulfur and chlorine
that were like those remaining after the evaporation of sea water. Sulfur was more concentrated in the crust on top of the soil than in the bulk soil beneath. The sulfur may be present as sulfates of sodium
, magnesium, calcium, or iron. A sulfide
of iron is also possible. The rovers Spirit
and the Opportunity
both found sulfates on Mars. Opportunity (landed in 2004 with advanced instruments) found magnesium sulfate and calcium sulfate at Meridiani Planum
. Using results from the chemical measurements, mineral models suggest that the soil could be a mixture of about 90% iron-rich clay
, about 10% magnesium sulfate
(kieserite
?), about 5% carbonate
(calcite
), and about 5% iron oxides (hematite
, magnetite
, goethite
?). These minerals are typical weathering products of mafic igneous rocks. All samples heated in the gas chromatograph-mass spectrometer (GSMS0] gave off water. However, the way the samples were handled precluded an exact measurement of the amount of water. But, it was around 1%. Studies with magnets aboard the landers indicated that the soil is between 3 and 7 percent magnetic materials by weight. The magnetic chemicals could be magnetite
and maghemite
. These could come from the weathering of basalt
rock. Experiments carried out by the Mars Spirit Rover (landed in 2004) indicated magnetite could explain the magnetic nature of the dust and soil on Mars. Magnetite (which is very dark) was found in the soil and the most magnetic part of the soil was dark.
in the Martian Soil. Perchlorate is a strong oxidant so it may have destroyed any organic matter on the surface. If it is widespread on Mars, carbon-based life would be difficult at the soil surface.
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;
see Shapiro delay
.
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
as part of NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
's Viking program
Viking program
The Viking program consisted of a pair of American space probes sent to Mars, Viking 1 and Viking 2. Each spacecraft was composed of two main parts, an orbiter designed to photograph the surface of Mars from orbit, and a lander designed to study the planet from the surface...
. It was the first spacecraft to successfully land on Mars and perform its mission, and until May 19, 2010 held the record for the second longest Mars surface mission of 6 years and 116 days (from landing until surface mission termination, Earth time).
Mission
Following launch using a TitanTitan IIIE
The Titan IIIE or Titan 3E, also known as Titan III-Centaur was an American expendable launch system, launched seven times between 1974 and 1977...
/Centaur
Centaur (rocket stage)
Centaur is a rocket stage designed for use as the upper stage of space launch vehicles. Centaur boosts its satellite payload to geosynchronous orbit or, in the case of an interplanetary space probe, to or near to escape velocity...
launch vehicle on August 20, 1975 and a 10-month cruise to Mars, the orbiter began returning global images of Mars about 5 days before orbit insertion. The Viking 1 Orbiter was inserted into Mars orbit on June 19, 1976 and trimmed to a 1513 x 33,000 km, 24.66 h site certification orbit on June 21. Landing on Mars was planned for July 4, 1976, the United States Bicentennial
United States Bicentennial
The United States Bicentennial was a series of celebrations and observances during the mid-1970s that paid tribute to the historical events leading up to the creation of the United States as an independent republic...
, but imaging of the primary landing site showed it was too rough for a safe landing. The landing was delayed until a safer site was found. The lander separated from the orbiter on July 20 08:51 UTC and landed at 11:53:06 UTC. It was the first attempt by the United States at landing on Mars.
Orbiter
The instruments of the orbiterOrbiter
An orbiter is a space probe that orbits a planet.-Asteroids:*NEAR Shoemaker...
consisted of two vidicon cameras for imaging (VIS), an infrared spectrometer for water vapor mapping (MAWD) and infrared radiometers for thermal mapping (IRTM). The orbiter
Orbiter
An orbiter is a space probe that orbits a planet.-Asteroids:*NEAR Shoemaker...
primary mission ended at the beginning of solar conjunction
Solar conjunction
Solar conjunction occurs when a planet or other solar system object is on the opposite side of the sun from the Earth. From an Earth reference, the object will pass between the sun and the Earth. Communication with any spacecraft in solar conjunction will be severely limited due to the sun's...
on November 5, 1976. The extended mission commenced on December 14, 1976 after solar conjunction. Operations included close approaches to Phobos
Phobos (moon)
Phobos is the larger and closer of the two natural satellites of Mars. Both moons were discovered in 1877. With a mean radius of , Phobos is 7.24 times as massive as Deimos...
in February 1977. The periapsis
Apsis
An apsis , plural apsides , is the point of greatest or least distance of a body from one of the foci of its elliptical orbit. In modern celestial mechanics this focus is also the center of attraction, which is usually the center of mass of the system...
was reduced to 300 km on March 11, 1977. Minor orbit adjustments were done occasionally over the course of the mission, primarily to change the walk rate — the rate at which the areocentric longitude changed with each orbit, and the periapsis was raised to 357 km on July 20, 1979. On August 7, 1980 Viking 1 Orbiter was running low on altitude control gas and its orbit was raised from 357 × 33943 km to 320 × 56000 km to prevent impact with Mars and possible contamination until the year 2019. Operations were terminated on August 17, 1980 after 1485 orbits.
Lander
The lander and its aeroshell separated from the orbiter on July 20 08:51 UTC. At the time of separation, the lander was orbiting at about 4 km/s. The aeroshell's retrorockets fired to begin the lander deorbit maneuver. After a few hours at about 300 km altitude, the lander was reoriented for atmospheric entry. The aeroshell with its ablative heat shieldHeat shield
A heat shield is designed to shield a substance from absorbing excessive heat from an outside source by either dissipating, reflecting or simply absorbing the heat...
slowed the craft as it plunged through the atmosphere. During this time, entry science experiments were performed by using a retarding potential analyzer, a mass spectrometer, and pressure, temperature and density sensors. At 6 km altitude, traveling at about 250 m/s, the 16 m diameter lander parachutes deployed. Seven seconds later the aeroshell was jettisoned, and 8 seconds after that the three lander legs were extended. In 45 seconds the parachute
Parachute
A parachute is a device used to slow the motion of an object through an atmosphere by creating drag, or in the case of ram-air parachutes, aerodynamic lift. Parachutes are usually made out of light, strong cloth, originally silk, now most commonly nylon...
had slowed the lander to 60 m/s. At 1.5 km altitude, retrorockets on the lander itself were ignited and, 40 seconds later at about 2.4 m/s, the lander arrived on Mars with a relatively light jolt. The legs had honeycomb aluminum shock absorbers to soften the landing.
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
Chryse Planitia
Chryse Planitia is a smooth circular plain in the northern equatorial region of Mars close to the Tharsis region to the west, centered at . Chryse Planitia lies partially in the Lunae Palus quadrangle and partially in the Oxia Palus quadrangle...
("Golden Plain") at 22.697°N 48.222°W 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. This first color image has since been lost or misplaced. Additionally, 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
Thomas A. Mutch
Thomas A. Mutch was an American geologist and planetary scientist. He was a professor at Brown University from 1960 until his death. He was presumed killed when he disappeared during descent from Mount Nun in the Kashmir Himalayas.He published two books about the geology of the Moon and of Mars...
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
Mars Reconnaissance Orbiter
Mars Reconnaissance Orbiter is a NASA multipurpose spacecraft designed to conduct reconnaissance and Exploration of Mars from orbit...
.
Analysis of soil
Samples resembled soil produced from weathering of basaltic lavaLava
Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...
s. The tested soil contained abundant silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
and iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
, along with significant amounts of magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
, aluminum, sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
, calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
, and titanium
Titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....
. Trace elements, strontium
Strontium
Strontium is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and...
and yttrium
Yttrium
Yttrium is a chemical element with symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanides and it has often been classified as a "rare earth element". Yttrium is almost always found combined with the lanthanides in rare earth minerals and is...
, were detected. The amount of potassium
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
was one fifth the average for the Earth's crust. Some chemicals in the soil contained sulfur and chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
that were like those remaining after the evaporation of sea water. Sulfur was more concentrated in the crust on top of the soil than in the bulk soil beneath. The sulfur may be present as sulfates of sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
, magnesium, calcium, or iron. A sulfide
Sulfide
A sulfide is an anion of sulfur in its lowest oxidation state of 2-. Sulfide is also a slightly archaic term for thioethers, a common type of organosulfur compound that are well known for their bad odors.- Properties :...
of iron is also possible. The rovers Spirit
Spirit rover
Spirit, MER-A , is a robotic rover on Mars, active from 2004 to 2010. It was one of two rovers of NASA's ongoing Mars Exploration Rover Mission. It landed successfully on Mars at 04:35 Ground UTC on January 4, 2004, three weeks before its twin, Opportunity , landed on the other side of the planet...
and the Opportunity
Opportunity rover
Opportunity, MER-B , is a robotic rover on the planet Mars, active since 2004. It is the remaining rover in NASA's ongoing Mars Exploration Rover Mission...
both found sulfates on Mars. Opportunity (landed in 2004 with advanced instruments) found magnesium sulfate and calcium sulfate at Meridiani Planum
Meridiani Planum
Meridiani Planum is a plain located 2 degrees south of Mars' equator , in the westernmost portion of Terra Meridiani. It hosts a rare occurrence of gray crystalline hematite...
. Using results from the chemical measurements, mineral models suggest that the soil could be a mixture of about 90% iron-rich clay
Clay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...
, about 10% magnesium sulfate
Magnesium sulfate
Magnesium sulfate is a chemical compound containing magnesium, sulfur and oxygen, with the formula MgSO4. It is often encountered as the heptahydrate epsomite , commonly called Epsom salt, from the town of Epsom in Surrey, England, where the salt was distilled from the springs that arise where the...
(kieserite
Kieserite
Kieserite is a highly unstable magnesium sulfate mineral . It has a vitreous luster and it is colorless, grayish-white or yellowish. Its hardness is 3.5 and it has a monoclinic crystal system...
?), about 5% carbonate
Carbonate
In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....
(calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...
), and about 5% iron oxides (hematite
Hematite
Hematite, also spelled as haematite, is the mineral form of iron oxide , one of several iron oxides. Hematite crystallizes in the rhombohedral system, and it has the same crystal structure as ilmenite and corundum...
, magnetite
Magnetite
Magnetite is a ferrimagnetic mineral with chemical formula Fe3O4, one of several iron oxides and a member of the spinel group. The chemical IUPAC name is iron oxide and the common chemical name is ferrous-ferric oxide. The formula for magnetite may also be written as FeO·Fe2O3, which is one part...
, goethite
Goethite
Goethite , named after the German polymath Johann Wolfgang von Goethe, is an iron bearing oxide mineral found in soil and other low-temperature environments. Goethite has been well known since prehistoric times for its use as a pigment. Evidence has been found of its use in paint pigment samples...
?). These minerals are typical weathering products of mafic igneous rocks. All samples heated in the gas chromatograph-mass spectrometer (GSMS0] gave off water. However, the way the samples were handled precluded an exact measurement of the amount of water. But, it was around 1%. Studies with magnets aboard the landers indicated that the soil is between 3 and 7 percent magnetic materials by weight. The magnetic chemicals could be magnetite
Magnetite
Magnetite is a ferrimagnetic mineral with chemical formula Fe3O4, one of several iron oxides and a member of the spinel group. The chemical IUPAC name is iron oxide and the common chemical name is ferrous-ferric oxide. The formula for magnetite may also be written as FeO·Fe2O3, which is one part...
and maghemite
Maghemite
Maghemite is a member of the family of iron oxides. It has the same structure as magnetite, that is, it is spinel ferrite and is also ferrimagnetic.Maghemite can be considered as an Fe-deficient magnetite with formula...
. These could come from the weathering of basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
rock. Experiments carried out by the Mars Spirit Rover (landed in 2004) indicated magnetite could explain the magnetic nature of the dust and soil on Mars. Magnetite (which is very dark) was found in the soil and the most magnetic part of the soil was dark.
Search for life
Viking carried a biology experiment whose purpose was to look for evidence of life. The Viking biology experiment weighed 15.5 kg (34 lbs) and consisted of three subsystems: the Pyrolytic Release experiment (PR), the Labeled Release experiment (LR), and the Gas Exchange experiment (GEX). In addition, independent of the biology experiments, Viking carried a Gas Chromatograph/Mass Spectrometer (GCMS) that could measure the composition and abundance of organic compounds in the martian soil. The results were surprising and interesting: the GCMS gave a negative result; the PR gave a negative result, the GEX gave a negative result, and the LR gave a positive result. Viking scientist Patricia Straat recently stated, "Our (LR) experiment was a definite positive response for life, but a lot of people have claimed that it was a false positive for a variety of reasons." Most scientists now believe that the data were due to inorganic chemical reactions of the soil; however, this view may be changing after the recent discovery of near-surface ice near the Viking landing zone. Some scientists still believe the results were due to living reactions. No organic chemicals were found in the soil. However, dry areas of Antarctica do not have detectable organic compounds either, but they have organisms living in the rocks. Mars has almost no ozone layer, unlike the Earth, so UV light sterilizes the surface and produces highly reactive chemicals such as peroxides that would oxidize any organic chemicals. The Phoenix Lander discovered the chemical perchloratePerchlorate
Perchlorates are the salts derived from perchloric acid . They occur both naturally and through manufacturing. They have been used as a medicine for more than 50 years to treat thyroid gland disorders. They are used extensively within the pyrotechnics industry, and ammonium perchlorate is also a...
in the Martian Soil. Perchlorate is a strong oxidant so it may have destroyed any organic matter on the surface. If it is widespread on Mars, carbon-based life would be difficult at the soil surface.
Test of general relativity
Gravitational time dilation
Gravitational time dilation is the effect of time passing at different rates in regions of different gravitational potential; the lower the gravitational potential, the more slowly time passes...
is a phenomenon predicted by the theory of General Relativity
General relativity
General relativity or the general theory of relativity is the geometric theory of gravitation published by Albert Einstein in 1916. It is the current description of gravitation in modern physics...
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;
see Shapiro delay
Shapiro delay
The Shapiro time delay effect, or gravitational time delay effect, is one of the four classic solar system tests of general relativity. Radar signals passing near a massive object take slightly longer to travel to a target and longer to return than it would if the mass of the object were not...
.
See also
- Viking 2Viking 2The Viking 2 mission was part of the American Viking program to Mars, and consisted of an orbiter and a lander essentially identical to that of the Viking 1 mission. The Viking 2 lander operated on the surface for 1,281 Mars days and was turned off on 11 April 1980 when its batteries failed...
- Exploration of MarsExploration of MarsThe exploration of Mars has been an important part of the space exploration programs of the Soviet Union, the United States, Europe, and Japan. Dozens of robotic spacecraft, including orbiters, landers, and rovers, have been launched toward Mars since the 1960s...
- Space explorationSpace explorationSpace exploration is the use of space technology to explore outer space. Physical exploration of space is conducted both by human spaceflights and by robotic spacecraft....
- Unmanned space mission
- Viking programViking programThe Viking program consisted of a pair of American space probes sent to Mars, Viking 1 and Viking 2. Each spacecraft was composed of two main parts, an orbiter designed to photograph the surface of Mars from orbit, and a lander designed to study the planet from the surface...
- U.S. Space Exploration History on U.S. StampsU.S. space exploration history on U.S. stampsWith the advent of unmanned and manned space flight a whole new era of American history had presented itself. Keeping with the tradition of honoring the country's history on the face of U.S. postage stamps, the U.S. Post Office began honoring the various events with its commemorative postage stamp...