Meridiani Planum

Meridiani Planum is a plain located 2 degrees south of Mars's equator (centered at 0°12′N 357°30′E / 0.2°N 357.5°E / 0.2; 357.5), 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.This image, taken by the microscopic imager, reveals shiny, spherical objects embedded within the trench wall'Blueberries' (hematite spheres) on a rocky outcrop at Eagle Crater. Note the merged triplet in the upper left.The rock 'Berry Bowl'.Drawing showing how 'blueberries' came to cover much of surface in Meridiani Planum.Heat Shield Rock was the first meteorite ever identified on another planet.Heat shield, with Heat Shield Rock just above and to the left in the background.Close view of layers, as seen by HiRISE under HiWish program At least one layer is light-toned which may indicated hydrated minerals.Close view of layers, as seen by HiRISE under HiWish program Meridiani Planum is a plain located 2 degrees south of Mars's equator (centered at 0°12′N 357°30′E / 0.2°N 357.5°E / 0.2; 357.5), 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. 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.