MIMOS II

MIMOS II (device with a circular disk in the center) of the Opportunity rover on Mars, February 3, 2004.

Mössbauer spectrum obtained by the rover Spirit in the Gusev crater. The spectrum contains an iron-containing mineral called goethite (FeO (OH)), in a stone called “Clovis” on the “Columbian Hills” of Mars. Goethite contains water in the form of a hydroxyl group in its structure. Having identified this mineral , the Clovis survey provided convincing evidence of past liquid water activity in the area that the Spirit rover was exploring.

MIMOS II is a miniature Mössbauer spectrometer developed by Dr. Göstar Klingelhofer at the University. Johannes Gutenberg in Mainz , Germany ^[1] . It was used on rovers of the NASA space agency, Spirit and Opportunity , to study the mineralogy of iron-bearing rocks and soils of the Martian surface. Mars is a particularly good place for Mössbauer spectroscopy, since its surface is rich in iron (~ 20% Fe in the form of Fe ₂ O ₃ ) ^[1] .

MIMOS II uses a cobalt-57 ( ⁵⁷ Co) gamma radiation source with an activity of about 300 mCi at the time of launch of the rovers ^[1] . To obtain the standard Mössbauer spectrum, it takes 6-12 hours at the time of the primary mission of the rovers (90salt ) on Mars, depending on the total content of iron and iron-containing phases ^[1] . ⁵⁷ Co has a half-life of only 271.8 days (therefore, the measurement time of samples with time will gradually increase until the radioactive isotope resource is completely exhausted) ^[1] .

MIMOS II on the surface of Mars provides identification of iron-containing phases (for example, oxides , silicates , sulfides , sulfates and carbonates ), quantitative measurements of the distribution of iron with varying degrees of oxidation (for example, Fe ²⁺ , Fe ³⁺ ) and quantitative measurements of the distribution of iron among iron-containing phases (for example, the relative proportions of iron in olivine , pyroxene and magnetite in basalt ) stones and soils ^[1] . MIMOS II data comes in addition to data from the APXS spectrometer and composite data from Mini-TES .

The main objective of MIMOS II was to detect the presence of iron compounds. Studies of El Capitan stone have confirmed the discovery of a mineral called jarosite . It contains hydroxyl groups , therefore it must be formed in contact with water. Thus, the presence of liquid water on Mars has been experimentally confirmed in the past.

The total weight of MIMOS II is about 500 grams. The device includes a detector with dimensions of about 9 cm × 5 cm × 4 cm and a weight of about 400 grams, located on the rover manipulator, as well as a printed circuit board, which has detector control circuits, data collection, storage, data transfer and other circuits. The board measures 16 cm × 10 cm × 2.5 cm, weighs about 100 grams and is located in the main “heat block with electronics” of the rover. The power consumption of MIMOS II is about 2 watts. The detector is capable of operating in the temperature range from −120 ° C to +40 ° C, and the printed circuit board from −50 ° C to +40 ° C ^[1] .

At the time of the completion of the mission of the Opportunity rover in 2019, MIMOS II was turned off for a long time, since the resource of the cobalt-57 ( ⁵⁷ Co) used was completely exhausted. In 2011, Opportunity spent several weeks analyzing one sample.