Scientific information from the Mars Exploration Rover mission

The two Mars Rover "Spirit" and "Opportunity" have during their long mission duration found numerous indications that indicate the former presence of water on Mars ( Planet). Some discoveries have already been prepared by Mars orbiters, while others are only carried out by the study of the rocks on the ground. Spirit explored during his mission in the Gusev crater time a hill and a former volcanic plateau called " Home Plate ". Opportunity found in the Meridiani different level evidence of formerly wet environment of the Martian surface.

The two landing sites ( Gusev crater and Meridiani level) were therefore chosen because were already out of orbit evidence that there water must have played a role. The instrumentation of the Rover with the two spectrometers (alpha particle X-ray spectrometer and Mössbauer spectrometer, the Panoramic Camera with different filters and the Mini - TES) is designed to analyze the rocks found by mineralogical point of view.

Water and salts

Salts are the products of a reaction of acid with a base (or alkali ). The result is a neutral substance, usually water. The chemical reactions that produce salts set, assume that the two components come together in an aqueous solution. Spirit and Opportunity have found that salts are commonly found on Mars.

Spirit drove toward the end of his mission on the slope of the plateau ' Home Plate ' in a crater filled with sand resistant. When an attempt was made to free the stuck rover out of the sand, the soil was partially dug. The driving tests promoted this bright floor to the left front wheel to light. This place was called ' Ulysses '. Come to the fore sulfates that were buried just below the surface. By combining the measurements of the Mössbauer spectrometer, the APX - spectrometer and the data of PanCam a self-consistent conclusion could be drawn that Ulysses contains moderately hydrated iron sulfates. These sulfates may have arisen from a volcanic steam source. The thin, crusty soil below the surface, which came to light on the eastern edge of Ulysses are enriched with hematite and iron sulfates. The most likely explanation for the occurrence of iron sulfates and basaltic sand inside the crater is that these minerals were flown here from other places and have accumulated as wind deposits. Then came episodic neutral to slightly acidic water in the soil in the valleys around home plate around on. A water-containing solution then seeped below the surface, leaving behind iron sulfate-containing layers only a few centimeters below the surface. The sulfate-rich deposits and encrusted soils follow the topography, this gives an indication of the timing of deposits. A conclusion can then be drawn that the formation of frost and snow this necessary amount of water delivered (eg, during a time when the Mars axis inclination had a higher than today ).

Spirit had partially dug with his fixed wheel during a drive on the east side of Home Plate on Sol 1148 the sand. What emerged was in this place, the " Gertrude way " was named, a white substance which turned out to be almost pure silicate. Spectra were recorded with the MINI- Tes, showed spectral properties that are associated with opaline silica. Recorded with the Pancam near-infrared reflectance spectra show features which are consistent with the presence of water in hydrated minerals. This deposition of almost pure silicate could have formed, is percolating as hot volcanic steam or hot water through the soil. Such deposits are also found on Earth in hot springs, such as in Yellowstone National Park.

The discovery of such deposits is an important point to assess whether the former environment of Mars has been worth living. On Earth exist in thermal springs, for example, flowering microbiological systems.

Blueberries: minerals that formed in acidic water

In Meridiani Planum, Opportunity landed in the small beads were soon discovered, were given the nickname " Blueberries ". Some of these are loosely distributed over the surface, sometimes still firmly embedded in the individual layers of stone. The distribution of Blueberries in the rock is more evenly than purely coincidental.

Here measurements with the Mössbauer spectrometer showed that this major consist of hematite. On Earth, hematite is formed mostly in water. Water is here oxygen atoms available to bind with the iron atoms in the mineral. On Mars, it is likely that ( acidic ) Ground water had dissolved iron. As it has flowed through the sandstone layers of the Meridiani plain, the iron could settle on these small beads were formed. This must be done in standing or slow- flowing groundwater, so that sufficient hematite was precipitated from the water. The beads are larger than those in higher layers at greater depths, suggesting that the effect of groundwater increased with increasing depth.

Sulfate

Sulfates needed only locally occurring for their education concentrations of salt water, which does not also have to be durable occurred over a longer period on the planet's surface.

Small gaps and cracks often form polygonal structures in the exposed surfaces of the Meridiani rocks. These cracks run through the existing rock stratification, so that it can be assumed that the cracks have appeared only after the deposition. If sulfates dry out, they lose a substantial part of its volume. The columns found could thus have arisen that the sulfate minerals reduced in volume due to water loss when the environmental conditions were dry.

Jarosit

In addition, Opportunity found directly at its landing site at Eagle Crater another mineral called " jarosite ". As hematite is jarosite forms in acidic water. In Jarosit water has a weight fraction of 10 %. The mineral is therefore a mineralogical evidence for the existence of water on Mars. In addition, it shows that in earlier times processes have proceeded with acidic water that gave rise to jarosite under oxidizing conditions.

The adjacent spectrum, which was created by the Mössbauer spectrometer, shows iron-containing jarosite minerals in the rock digestion called " El Capitain ". The two peaks in the yellow diagram indicates jarosite containing water in the form of hydroxyl in the structure. The data show that water- driven processes exist or have existed on Mars.

Traces of dissolved minerals

Show images from Opportunity's Pancam and the Microscopic Imager that the digestion " El Capitain " is covered with elongated cavities ( vugs ) of approximately 1 cm in length and a width of 1-2 mm in different orientations. The cavities are unevenly distributed in Eagle Crater. In the rocks in which they occur, they cover about 5 % of the surface. Geologists is that specific patterns of known locations at which saline minerals deposited within stones that lie in salty water. If the crystals remain dissolve later in not quite as salty water back these cavities ( geodes ).

Clay minerals

At the edge of Endeavour crater Opportunity searched for clay minerals whose signatures appear in spectral recordings from orbit. The sulfate minerals found so far were located in a mix of minerals and acidic water. Thus, an acidic environment represents a rather poor basis for

However, the clay minerals on Mars were formed in pH neutral water. This finding points to a temporary live -friendly environment. For the formation of clay minerals must have interacted on the Martian surface for an extended period with water.

Carbonates

In a rock digestion called " Comanche ", which was examined by Spirit in December 2005 also minerals were found, which had been formed in neutral water. Spirit examined this rock with the Mössbauer spectrometer, the minites and the APXS spectrometer. In 2010, scientists were able to show from these data that a quarter of the rock consists of Magnesiumeisenkarbonat. This concentration is up to 10 times higher than any previously studied stone.

Carbonates occur in wet, near-neutral conditions, but dissolves in acid soon back on. This discovery is the first clear indication of the rovers that in earlier times the surface of Mars was life- friendly than the acidic environments that have been found so far.

The carbonates in Gusev crater encamped probably from carbonate solutions under hydrothermal conditions at near neutral pH value, in connection with volcanic activity during the Noachian era. The discovery of high concentrations of carbonates in Comanche digestion is the basis for climate models, which include CO2 as a greenhouse gas for a wet and warm Mars and predict followed by deposition of at least parts of the atmosphere in carbonate minerals.

Gypsum

The Endeavour crater is 4 billion years old and has a diameter of 22 km. Near the southern end of Cape York was explored by Opportunity of Odyssey crater. This is surrounded by a field of rocks that were ejected on impact. A rock called " Tisdale " was investigated here in detail because it offered access to older rock. APXS measurements showed that here one of the highest concentrations of zinc occur that have previously been measured on Mars. The heating of the ground by the impact that produced a crater the size of Endeavour crater was sufficient to cause hydrothermal activities when water is present. In stone Tisdale took Opportunity evidence that the original impact has heated groundwater that had these zinc enrichment left behind in stone.

Cape York is surrounded by a gently sloping terrace, which is about 6 feet wide on the west side, and about 20 m to the east of the Endeavour crater facing page. The outer parts of the terrace on the western side are exposed, light thin stratified sandstones whose stratification slopes gently towards the plane. These sandstone layers lie directly over darker -grained sedimentary rocks that form the inner edge of the terrace. This arrangement is interpreted as the " Burns" Formation rests on the older sedimentary material of the " Shoemaker " formation. The inner edges of the terraces overlap the breccias from the Noachian era, which form the inner slopes of Cape York.

The rocks of the terraces are traversed in many places by bright linear veins. These are easily visible in projecting dark sediment material on the inside of the terraces. However, they also occur in the bright outcrops of sandstone on the Burns formation. Measurements of 37 vein yielded an average width of 2 cm and an average visible length of 33 cm.

Opportunity discovered on the edge of Cape York, this eye-catching bright rock lines ( veins), which were examined in detail. The vein " Homestake " for example, forming a non- continuous ridge with a width of 1-1.5 cm and about 50 cm long. It is about 1 cm above the surrounding rock. So you seem to be against erosion than the rock in which it is embedded resistant.

These veins may have occurred after the impact, as colder water flowed through cracks in the ground near the crater. It was deposited gypsum, which developed itself as veins along the columns. Gypsum is the most common mineral in the earth and sulfate is often left as the remainder, when the water is evaporated. These bright mineral vein has yet been found anywhere on Mars.

Ripple: Petrified shore sand

In the rocks in Eagle Crater and the Erebus hangover garland- like, ripple- shaped oblique layers are visible. These stratifications with only a thickness of 0.8 to 1.8 cm are probably the result of running water. The found arrangement of layers indicates that sediment transport by ripple below the water surface. It is known that the formation of such deposits in this size only under water and at flow velocities of a few tens of centimeters per second. Such wave-like ripple structures are formed on earth eg on sandy beaches. The lower compared to Earth Mars gravity has only a minor effect on the sediment transport and the size of the structures found.

These necessary for this purpose, probably under-drained, water currents may have been driven by the gravity of Mars. These currents caused by recurrent flooding of the salt flats, which covered the surface of Meridiani.