 Lander shell (top) and orbiter | |
| Mission type | Mars Orbiter/lander |
|---|---|
| Operator | NASA |
| COSPAR ID | |
| SATCATno. |
|
| Website | Viking Project Information |
| Mission duration | Orbiter: 1050 days (1022 sol)[1] Lander: 1316 days (1281 sol)[1] Launch to last contact: 1,676 days |
| Spacecraft properties | |
| Manufacturer | Orbiter:JPL Lander:Martin Marietta |
| Launch mass | 3,530 kg[a] |
| Dry mass | Orbiter: 883 kg (1,947 lb) Lander: 572 kg (1,261 lb)[2] |
| Power | Orbiter: 620 W Lander: 70 W |
| Start of mission | |
| Launch date | 18:39, September 9, 1975 (UTC) (1975-09-09T18:39:00Z)[1][3] |
| Rocket | Titan IIIE |
| Launch site | Cape CanaveralLC-41 |
| Contractor | Martin Marietta |
| End of mission | |
| Last contact | April 12, 1980 (1980-04-12)[4] |
| Orbital parameters | |
| Reference system | Areocentric |
| Eccentricity | 0.81630 |
| Periareion altitude | 300 km (190 mi) |
| Apoareion altitude | 33,176 km (20,615 mi) |
| Inclination | 80.5° |
| Period | 24.08 hours |
| Epoch | July 24, 1980 |
| Mars orbiter | |
| Spacecraft component | Viking 2 Orbiter |
| Orbital insertion | August 7, 1976[1][3] |
| Mars lander | |
| Spacecraft component | Viking 2 Lander |
| Landing date | September 3, 1976 22:37:50UTC (MSD 36500 00:13AMT)[1] |
| Landing site | 47°38′N225°43′W / 47.64°N 225.71°W /47.64; -225.71 (Viking 2 lander)[1] |
 Large Strategic Science Missions Planetary Science Division | |
TheViking 2 mission was part of the AmericanViking program toMars, and consisted of an orbiter and a lander essentially identical to that of theViking 1 mission.[1]Viking 2 was operational on Mars for 1281sols (1,316days;3 years, 221 days). TheViking 2 lander operated on the surface for 1,316 days, or 1281 sols, and was turned off on April 12, 1980, when its batteries eventually failed. The orbiter worked until July 25, 1978,[1] returning almost 16,000 images in 706 orbits around Mars.[5]
The craft was launched on September 9, 1975. Following launch using aTitan/Centaur launch vehicle and a 333-day cruise to Mars, theViking 2Orbiter began returning global images of Mars prior to orbit insertion. The orbiter was inserted into a 1,500 x 33,000 km, 24.6 hMars orbit on August 7, 1976, and trimmed to a 27.3 h site certification orbit with aperiapsis of 1,499 km and an inclination of 55.2 degrees on August 9. The orbiter then began taking photographs of candidate landing sites, which were used to select the final landing site.[6]
The lander separated from the orbiter on September 3, 1976, at 22:37:50UT and landed atUtopia Planitia.[7] The normal procedure called for the structure connecting the orbiter and lander (the bioshield) to be ejected after separation. However, due to problems with the separation process, the bioshield remained attached to the orbiter. The orbit inclination was raised to 75 degrees on September 30, 1976.[8]
The orbiter's primary mission ended on October 5, 1976, at the beginning ofsolar conjunction. The extended mission commenced on December 14, 1976, after the solar conjunction. On December 20, 1976, the periapsis was lowered to 778 km, and the inclination raised to 80 degrees.
Operations included close approaches toDeimos in October 1977, and the periapsis was lowered to 300 km and the period changed to 24 hours on October 23, 1977. The orbiter developed a leak in its propulsion system that vented itsattitude control gas. It was placed in a 302 × 33,176 km orbit and turned off on July 25, 1978, after returning almost 16,000 images in about 700–706 orbits around Mars.[9]
The lander and itsaeroshell separated from the orbiter on September 3, 1976, at 19:39:59 UT. At the time of separation, the lander was orbiting at about 4 km/s. After separation, rockets fired to begin landerdeorbit. After a few hours, at about 300 km attitude, the lander was reoriented for entry. The aeroshell with its ablativeheat shield slowed the craft as it plunged through the atmosphere.
TheViking 2 lander touched down about 200 km west of the crater Mie inUtopia Planitia at48°16′08″N225°59′24″W / 48.269°N 225.990°W /48.269; -225.990 at an altitude of -4.23 km relative to a reference ellipsoid with an equatorial radius of 3,397.2 km and aflattening of 0.0105 (47°58′01″N225°44′13″W / 47.967°N 225.737°W /47.967; -225.737 (Viking 2 landing site planetographic)planetographic longitude) at 22:58:20 UT (9:49:05 a.m. local Mars time).
Approximately 22 kg (49 lb) of propellants were left at landing. Due to radar misidentification of a rock or highly reflective surface, the thrusters fired an extra time 0.4 seconds before landing, cracking the surface and raising dust. The lander settled down with one leg on a rock, tilted at 8.2 degrees. The cameras began taking images immediately after landing.
TheViking 2 lander was powered by radioisotope generators and operated on the surface until its batteries failed on April 12, 1980.
In July 2001, theViking 2 lander was renamed theGerald Soffen Memorial Station afterGerald Soffen (1926–2000), the project scientist of theViking program.[6][10]
The regolith, referred to often as "soil", resembled those produced from the weathering of basalticlavas. The tested soil contained abundantsilicon andiron, along with significant amounts ofmagnesium,aluminum,sulfur,calcium, andtitanium. Trace elements,strontium andyttrium, were detected.
The amount ofpotassium was one-fifth of the average for the Earth's crust. Some chemicals in the soil contained sulfur andchlorine that were like those remaining after the evaporation of seawater. Sulfur was more concentrated in the crust on top of the soil than in the bulk soil beneath.
The sulfur may be present assulfates ofsodium, magnesium, calcium, or iron. Asulfide of iron is also possible.[11] TheSpirit rover and theOpportunity rover both found sulfates on Mars.[12]
Minerals typical weathering products ofmaficigneous rocks were found.[13] All samples heated in thegas chromatograph-mass spectrometer (GCMS) gave off water.
However, the way the samples were handled prohibited an exact measurement of the amount of water. But, it was around 1%.[14] Studies withmagnets aboard the landers indicated that the soil is between 3 and 7 percent magnetic materials by weight. The magnetic chemicals could bemagnetite andmaghemite, which could come from the weathering ofbasalt rock.[15][16] Subsequent experiments carried out by the MarsSpirit rover (landed in 2004) suggest that magnetite could explain the magnetic nature of the dust and soil on Mars.[17]
Viking 2 carried a biology experiment whose purpose was to look for life. TheViking 2 biology experiment weighed 15.5 kg (34 lb) and consisted of three subsystems: thePyrolytic Release experiment (PR), the Labeled Release experiment (LR), and the Gas Exchange experiment (GEX). In addition, independent of the biology experiments,Viking 2 carried a Gas Chromatograph/Mass Spectrometer (GCMS) that could measure the composition and abundance of organic compounds in the Martian soil.[18]
The results were unusual and conflicting: the GCMS and GEX gave negative results, while the PR and LR gave positive results.[19] Viking scientist Patricia Straat stated in 2009, "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."[20]
Many scientists believe that the data results were attributed to inorganic chemical reactions in the soil. However, this view may be changing due to a variety of discoveries and studies since Viking. These include the discovery of near-surface ice near the Viking landing zone, the possibility of perchlorate destruction of organic matter, and the reanalysis of GCMS data by scientists in 2018.[21] Some scientists still believe the results were due to living reactions. The formal declaration at the time of the mission was that the discovery of organic chemicals was inconclusive.[citation needed]
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.[22] ThePhoenix Lander discovered the chemicalperchlorate in the Martian soil. Perchlorate is a powerful oxidizing agent, which could have eradicated any organic material on the surface.[23] Perchlorate is now considered widespread on Mars, making it hard to detect any organic compounds on the Martian surface.[24]
.jpg)
.jpg)
The Viking Orbiters led to significant discoveries about the presence of water on Mars. Huge river valleys were found in many areas. They showed that water floods carved deep valleys, eroded grooves into bedrock, and traveled thousands of kilometers. In the southern hemisphere, the presence of branched stream areas suggests that there was once rainfall.[25][26][27]
The images below are mosaics of many small, high-resolution images.
| Rovers |  | |
|---|---|---|
| Helicopter | ||
| Landers | ||
| Memorial sites | ||
| Sample depots | ||
† indicates a mission failure (no significant data returned from the surface). | ||
| Active |
|  .jpg) .jpg) | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Past |
| ||||||||||
| |||||||||||
| Future |
| ||||||||||
| |||||||||||
| Exploration |
| ||||||||||
Missions are ordered by launch date. Sign† indicates failure en route or before intended mission data returned.‡ indicates use of the planet as agravity assist en route to another destination. | |||||||||||
