Meridiani Planum is a plain located 2 degrees south of Mars's equator (centered at ), in the westernmost portion of Terra Meridiani. It hosts a rare occurrence of gray crystalline hematite. On Earth, hematite is often formed in hot springs or in standing pools of water; therefore, many scientists believe that the hematite at Meridiani Planum may be indicative of ancient hot springs or that the environment contained liquid water. The hematite is part of a layered sedimentary rock formation about 200 to 800 meters thick. Other features of Meridiani Planum include volcanic basalt and impact craters.
Meridiani Planum was chosen as the landing site for the spacecraft landings of MER-B and the ExoMars EDM, the flat terrain, low-elevation, and relative lack of rocks and craters have made it favored location. This region also contains Challenger Memorial Station.
Mars Exploration Rover Opportunity looks southwest across Meridiani Planum; the Rover's discarded backshell and parachute are visible in the distance.
In 2004, Meridiani Planum was the landing site for the second of NASA's two Mars Exploration Rovers, named Opportunity. It had also been the target landing site for Mars Surveyor 2001 Lander, which was cancelled after the failures of the Mars Climate Orbiter and Mars Polar Lander missions.
Results from Opportunity indicate that its landing site was once saturated for a long period of time with liquid water, possibly of high salinity and acidity. Features that suggest this include cross-bedded sediments, the presence of many small spherical pebbles that appear to be concretions, vugs inside rocks, and the presence of large amounts of magnesium sulfate and other sulfate-rich minerals such as jarosite.
Opportunity rover found that the soil at Meridiani Planum was very similar to the soil at Gusev Crater and Ares Vallis; however in many places at Meridiani the soil was covered with round, hard, gray spherules that were named “blueberries.” These blueberries were found to be composed almost entirely of the mineral hematite. It was decided that the spectra signal spotted from orbit by Mars Odyssey was produced by these spherules. After further study it was decided that the blueberries were concretions formed in the ground by water. Over time, these concretions weathered from what was overlying rock, and then became concentrated on the surface as a lag deposit. The concentration of spherules in bedrock could have produced the observed blueberry covering from the weathering of as little as one meter of rock. Most of the soil consisted of olivine basalt sands that did not come from the local rocks. The sand may have been transported from somewhere else.
A Mössbauer spectrum was made of the dust that gathered on Opportunity's capture magnet. The results suggested that the magnetic component of the dust was titanomagnetite, rather than just plain magnetite, as was once thought. A small amount of olivine was also detected which was interpreted as indicating a long arid period on the planet. On the other hand, a small amount of hematite that was present meant that there may have been liquid water for a short time in the early history of the planet. Because the Rock Abrasion Tool (RAT) found it easy to grind into the bedrock, it is thought that the rocks are much softer than the rocks at Gusev Crater.
Few rocks were visible on the surface where Opportunity landed, but bedrock that was exposed in craters was examined by the suite of instruments on the Rover. Bedrock rocks were found to be sedimentary rocks with a high concentration of sulfur in the form of calcium and magnesium sulfates. Some of the sulfates that may be present in bedrocks are kieserite, sulfate anhydrate, bassanite, hexahydrite, epsomite, and gypsum. Salts, such as halite, bischofite, antarcticite, bloedite, vanthoffite, or gluberite may also be present.
The rocks contained the sulfates had a light tone compared to isolated rocks and rocks examined by landers/rovers at other locations on Mars. The spectra of these light toned rocks, containing hydrated sulfates, were similar to spectra taken by the Thermal Emission Spectrometer on board the Mars Global Surveyor. The same spectrum is found over a large area, so it is believed that water once appeared over a wide region, not just in the area explored by Opportunity rover.
The Alpha Particle X-ray Spectrometer (APXS) found rather high levels of phosphorus in the rocks. Similar high levels were found by other rovers at Ares Vallis and Gusev Crater, so it has been hypothesized that the mantle of Mars may be phosphorus-rich. The minerals in the rocks could have originated by acid weathering of basalt. Because the solubility of phosphorus is related to the solubility of uranium, thorium, and rare earth elements, they are all also expected to be enriched in rocks.
When Opportunity rover traveled to the rim of Endeavour Crater, it soon found a white vein that was later identified as being pure gypsum. It was formed when water carrying gypsum in solution deposited the mineral in a crack in the rock. A picture of this vein, called "Homestake" formation, is shown below.
Examination of Meridiani rocks found strong evidence for past water. The mineral called jarosite which only forms in water was found in all bedrocks. This discovery proved that water once existed in Meridiani Planum In addition, some rocks showed small laminations (layers) with shapes that are only made by gently flowing water. The first such laminations were found in a rock called “The Dells.” Geologists would say that the cross-stratification showed festoon geometry from transport in subaqueous ripples. A picture of cross-stratification, also called cross-bedding, is shown on the left.
Box-shaped holes in some rocks were caused by sulfates forming large crystals, and then when the crystals later dissolved, holes, called vugs, were left behind. The concentration of the element bromine in rocks was highly variable probably because it is very soluble. Water may have concentrated it in places before it evaporated. Another mechanism for concentrating highly soluble bromine compounds is frost deposition at night that would form very thin films of water that would concentrate bromine in certain spots.
One rock, “Bounce Rock,” found sitting on the sandy plains was found to be ejecta from an impact crater. Its chemistry was different than the bedrocks. Containing mostly pyroxene and plagioclase and no olivine, it closely resembled a part, Lithology B, of the shergottite meteorite EETA 79001, a meteorite known to have come from Mars. Bounce rock received its name by being near an airbag bounce mark.
Opportunity rover found meteorites just sitting on the plains. The first one analyzed with Opportunity's instruments was called “Heatshield Rock,” as it was found near where Opportunity's headshield landed. Examination with the Miniature Thermal Emission Spectrometer (Mini-TES), Mossbauer spectrometer, and APXS lead researchers to, classify it as an IAB meteorite. The APXS determined it was composed of 93% iron and 7% nickel. The cobble named “Fig Tree Barberton” is thought to be a stony or stony-iron meteorite (mesosiderite silicate), while “Allan Hills,” and “Zhong Shan” may be iron meteorites.
Observations at the site have led scientists to believe that the area was flooded with water a number of times and was subjected to evaporation and desiccation. In the process sulfates were deposited. After sulfates cemented the sediments, hematite concretions grew by precipitation from groundwater. Some sulfates formed into large crystals which later dissolved to leave vugs. Several lines of evidence point toward an arid climate in the past billion years or so, but a climate supporting water, at least for a time, in the distant past.
Parts of Meridiani Planum display layered features from orbit. Layers may have been formed with the aid of water, especially ground water.
A detailed discussion of layering with many Martian examples can be found in Sedimentary Geology of Mars.
Airy is an impact crater on Mars, named in honor of the British Astronomer, Royal Sir George Biddell Airy (1801–1892). The crater is approximately 43 kilometres (27 mi) in diameter and is located at 0.1°E 5.1°S in the Meridiani Planum region. The much smaller crater Airy-0, which defines the location of Mars' prime meridian, lies within it.Argo (crater)
Argo is a crater in the Meridiani Planum on Mars, which was visited by the Opportunity rover on approximately its 365th Martian sol. The crater is about 300 meters (980 ft) south of the heat shield and Heat Shield Rock.Beer (Martian crater)
Beer is a crater lying situated within the Margaritifer Sinus quadrangle (MC-19) region of the planet Mars, named in honor of the German astronomer, Wilhelm Beer. It is located at 14.4°S 351.8°E .
Beer and collaborator Johann Heinrich Mädler produced the first reasonably good maps of Mars in the early 1830s. When doing so, they selected a particular feature for the prime meridian of their charts. Their choice was strengthened when Giovanni Schiaparelli used the same location in 1877 for his more famous maps of Mars. The feature was later called Sinus Meridiani ("Middle Bay"), but following the landing of the NASA probe MER-B Opportunity in 2004 it is perhaps better known as Meridiani Planum. Currently the Martian prime meridian is the crater Airy-0.
Beer lies in the southwest of Meridiani Planum, about 8° from the prime meridian and about 10° west from the crater Mädler. Schiaparelli is also in the region.Cape Verde (Mars)
Cape Verde is a large promontory and extremity on the rim of Victoria Crater in Meridiani Planum, an extraterrestrial plain within the Margaritifer Sinus quadrangle (MC-19) region of the planet Mars. The Mars Exploration Rover Opportunity perched atop this feature in 2006 to take a true-color mosaic of the crater below. Sols 958 to 991 were spent on this cape, including the period of solar conjunction which spanned from sol 970 to sol 984.Cape Verde and neighboring Cabo Frio are named after Cape Verde and Cabo Frio, places visited on Ferdinand Magellan's voyage around the world by the ship Victoria.Eagle (Meridiani Planum crater)
Eagle is a 22-metre long impact crater located on the Meridiani Planum extraterrestrial plain, situated within the Margaritifer Sinus quadrangle (MC-19) portion of the planet Mars. The Opportunity rover came to rest inside Eagle crater when it landed in 2004. Scientists were delighted that the rover landed there, as the crater contains rocky outcroppings that helped prove that Meridiani was once an ocean floor.
This crater should not be confused with the other, much larger Martian crater Eagle, which was officially named by IAU's Working Group for Planetary System Nomenclature in 1976.Emma Dean (crater)
Emma Dean is a small impact crater in the Meridiani Planum extraterrestrial plain situated within the Margaritifer Sinus quadrangle (MC-19) region of the planet Mars. This geological feature was visited by the Opportunity rover from sols 929 to 943. The much larger crater Victoria lies about 100m to the east.
Emma Dean lies directly on top of the ejecta blanket from Victoria and could therefore expose material originating from deep inside Victoria.
The crater is named after Emma Dean, John Wesley Powell's wife and one of the boats in Grand Canyon Powell expedition.Endurance (crater)
Endurance is an impact crater lying situated within the Margaritifer Sinus quadrangle (MC-19) region of the planet Mars. This crater was visited by the Opportunity rover from May until December 2004. Mission scientists named the crater after the ship Endurance that sailed to the Antarctic through the Weddell Sea during the ill-fated 1914-1917 Imperial Trans-Antarctic Expedition, considered to be the last expedition of the Heroic Age of Antarctic Exploration organized by Ernest Shackleton.
The rover entered the crater interior on its 134th mission sol (June 15), and exited on the 315th sol (December 14). During this time it traversed various obstacles, steep inclines, and overcame large wheel slippage when driving over fine sand.Erebus (crater)
Erebus is a crater lying situated within the Margaritifer Sinus quadrangle (MC-19) region of the planet Mars, this extraterrestrial geological feature was visited by the Opportunity rover on the way to the much larger crater Victoria. It is named after the polar exploration vessel HMS Erebus which was used by James Clark Ross in 1841 to discover the Great Ice Barrier, now known as the Ross Ice Shelf. The rover was in the immediate vicinity of the crater from approximately sol 550 to 750 (October 2005 to March 2006).
This crater features two other minor named outcrops on the edges of this topographical depression. These include Payson Ridge and Olympia Ridge (see gallery below).
Erebus is located roughly 2,500 metres (8,200 ft) south of the much smaller crater Vostok, which was previously visited by Opportunity. It is surrounded by what scientists are describing as "etched terrain", a region where rocks peek out from under the sand of Meridiani Planum.Erebus is about 350 metres (1,150 ft) wide, twice as large as the crater Endurance. However, it is very old and eroded, and is barely visible from the ground; it appears merely as a number of flat rocky outcrops encircling a region of dunes.Fram (crater)
Fram is an impact crater located within the Meridiani Planum extraterrestrial plain, situated within the Margaritifer Sinus quadrangle (MC-19) region of the planet Mars. It was visited by the rover Opportunity (MER-B) on Sol 84, April 24, 2004.
Fram spans about 8 metres (26 feet) in diameter. Opportunity paused beside it while travelling from the rover's landing site toward a larger crater, Endurance. Fram is located about 450 metres (0.3 miles) east of the crater Eagle and around 250 metres (820 feet) west of Endurance.
It is named after the famous Norwegian polar exploration vessel the Fram, a ship used by many famous Norwegian explorers such as Fridtjof Nansen, Otto Sverdrup, Oscar Wisting, and Roald Amundsen.Heat Shield Rock
Heat Shield Rock is a basketball-sized iron-nickel meteorite found on Mars by the Mars rover Opportunity in January 2005. The meteorite was formally named Meridiani Planum meteorite by the Meteoritical Society in October, 2005 (meteorites are always named after the place where they were found).Henry (Martian crater)
Henry Crater is a large crater in the Arabia quadrangle of Mars, located at 10.9° north latitude and 23.3° east longitude. It is 171 kilometres (106 mi) in diameter and was named after the brothers Paul Henry and Prosper Henry, both of whom were French telescope makers and astronomers.Iazu (crater)
Iazu is an impact crater located within the Meridiani Planum extraterrestrial plain, situated within the Margaritifer Sinus quadrangle (MC-19) region of the planet Mars. This geological feature is about 7 km in diameter. It is close to the landing site of the Mars Exploration Rover-B Opportunity, and its walls have been photographed by the spacecraft during its traverse to Endeavour Crater. At the time, the crater was about 38 kilometers (24 mi) away. It was named in 2006 for Iazu, a commune in Dâmboviţa County, southern Romania.Bopolu (crater) is west of Iazu and Endeavour craterList of surface features of Mars imaged by Opportunity
The following is a list of surface features of Mars imaged by the Opportunity rover. Opportunity landed in Meridiani Planum in 2004. (See also Opportunity mission timeline)Mackinac Island meteorite
Mackinac Island meteorite was found on Mars by the Opportunity rover on October 13, 2009.Mädler (Martian crater)
Mädler is a crater on Mars named in honor of the German astronomer Johann Heinrich Mädler. It is located at 2.7°E 10.7°S.
Mädler and collaborator Wilhelm Beer produced the first reasonably good maps of Mars in the early 1830s. When doing so, they selected a particular feature for the prime meridian of their charts. Their choice was strengthened when Giovanni Schiaparelli used the same location in 1877 for his more famous maps of Mars. The feature was later called Sinus Meridiani ("Middle Bay" or "Bay of the Meridian"), but following the landing of the NASA probe MER-B Opportunity in 2004 is perhaps better known as Meridiani Planum.
Mädler lies in the south of Meridiani Planum, close to the prime meridian and about 10° east of Beer. Schiaparelli is also in the region.Nereus (crater)
Nereus is a small impact crater lying situated within the Margaritifer Sinus quadrangle (MC-19) region of the planet Mars with a diameter of about 10 metres (33 ft). It is located just south of the planet's equator on the relatively smooth Meridiani Planum (plain).It was discovered by the Opportunity Mars rover on Sol 2010 (2009-09-19), being noticed because it is surrounded by jagged rocks, and was the Astronomy Picture of the Day for 2009-10-19.
It is named for Nereus, a Greek god who lived with the Nereids in the Aegean Sea.Santa Maria (crater)
Santa Maria is an impact crater on Mars, located at 2.172°S, 5.445°W within the Meridiani Planum extraterrestrial plain, lying situated within the Margaritifer Sinus quadrangle (MC-19) region.
This geological feature was first visited by the Mars Exploration Rover Opportunity. It sits north west of the much larger Endeavour crater. The crater measures about 80–90 m (260–300 ft) across. Its name has not been officially recognized by the Working Group for Planetary System Nomenclature.Sinus Meridiani
Sinus Meridiani is an albedo feature on Mars stretching east-west just south of that planet's equator. It was named by the French astronomer Camille Flammarion in the late 1870s.
In 1979-2001, the vicinity of this feature (with size about 1600 km and coordinates of the center 7.12 S and 4 E) was named Terra Meridiani.Victoria (crater)
Victoria is an impact crater on Mars located at 2.05°S, 5.50°W in the Meridiani Planum extraterrestrial plain, lying situated within the Margaritifer Sinus quadrangle (MC-19) region of the planet Mars. This crater was first visited by the Mars Exploration Rover Opportunity. It is roughly 730 metres wide, nearly eight times the size of the crater Endurance, visited by Opportunity from sols 951 to 1630. It is informally named after Victoria – one of the five Spanish ships of Ferdinand Magellan and the first ship to circumnavigate the globe – and formally named after Victoria, Seychelles. Along the edges of the crater are many outcrops within recessed alcoves and promontories, named for bays and capes that Magellan discovered.
Opportunity traveled for 21 months to Victoria before finally reaching its edge on September 26, 2006 (sol 951), at the newly named "Duck Bay". Around the rover were features dubbed "No Name", "Duck Crater", "Emma Dean", "Maid of the Canyon", and "Kitty Clyde's Sister". It also imaged several nearby alcoves, informally named "Cape Verde" and "Cabo Frio", and a small bright crater the size of Beagle on the opposite end of Victoria.
Mars Exploration Rover (MER) program