Moonmilk
Encyclopedia
Moonmilk is a white, creamy substance found inside cave
s. It is similar to other deposits, but its unique quality is that it does not harden or turn to stone. It is a precipitate from limestone
comprising aggregates of fine crystal
s of varying composition usually made of carbonate
materials, e.g., calcite
, hydromagnesite
, and monohydrocalcite
.
Hypotheses about the origin of moonmilk are mixed. Some scientists think it is a bacterial action rather than a chemical one. In this theory, it is thought to be created by the bacterium Macromonas bipunctata. Certain bacterial actions are known to be capable of breaking down stone to form this semiliquid "milk". However, no microbiological studies have been carried out so far.
It was originally thought (by Conrad Gesner, 1555) to be created by "moon
rays."
The discovery of a 150 meter long moonmilk river was first announced on March 2004 by a team of speleologists
in a cavern in Guipúzcoa, Spain
. This river is formed by a thick milk-like fluid composed by calcite, quarz and brushite
.
It is possible that moonmilk is formed by extruding water percolations that dissolve and soften the carbonate walls of karstic caves and carry dissolved nutrients that can be used by epilithic microbes, such as actinomycetes. As the microbial colonies grow, they trap and accumulate chemically-precipitated crystals in the organic matter-rich matrix formed that way. Perhaps these heterotrophic microbes, which produce CO2 as a waste product of respiration
and maybe organic acids, help to dissolve the carbonate as well. Of course, more research is needed to prove any current hypothesis.
Cave
A cave or cavern is a natural underground space large enough for a human to enter. The term applies to natural cavities some part of which is in total darkness. The word cave also includes smaller spaces like rock shelters, sea caves, and grottos.Speleology is the science of exploration and study...
s. It is similar to other deposits, but its unique quality is that it does not harden or turn to stone. It is a precipitate from limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
comprising aggregates of fine crystal
Crystal
A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...
s of varying composition usually made of carbonate
Carbonate
In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....
materials, e.g., calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...
, hydromagnesite
Hydromagnesite
Hydromagnesite is a hydrated magnesium carbonate mineral with the formula: Mg542.4H2O.It generally occurs associated with the weathering products of magnesium containing minerals such as serpentine or brucite. It occurs as incrustations and vein or fracture fillings in ultramafic rocks and...
, and monohydrocalcite
Monohydrocalcite
Monohydrocalcite is a mineral that is a hydrous form of calcium carbonate, CaCO3·H2O. It was formerly also known by the name hydrocalcite, which is now discredited by the IMA. It is a trigonal mineral which is white when pure...
.
Hypotheses about the origin of moonmilk are mixed. Some scientists think it is a bacterial action rather than a chemical one. In this theory, it is thought to be created by the bacterium Macromonas bipunctata. Certain bacterial actions are known to be capable of breaking down stone to form this semiliquid "milk". However, no microbiological studies have been carried out so far.
It was originally thought (by Conrad Gesner, 1555) to be created by "moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
rays."
The discovery of a 150 meter long moonmilk river was first announced on March 2004 by a team of speleologists
Speleology
Speleology is the scientific study of caves and other karst features, their make-up, structure, physical properties, history, life forms, and the processes by which they form and change over time...
in a cavern in Guipúzcoa, Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
. This river is formed by a thick milk-like fluid composed by calcite, quarz and brushite
Brushite
Brushite is a mineral with the chemical formula . It is believed to be a precursor of apatite and is found in guano-rich caves, formed by the interaction of guano with calcite and clay at a low pH. Brushite was first described in 1865 and named for the American mineralogist George Jarvis Brush...
.
It is possible that moonmilk is formed by extruding water percolations that dissolve and soften the carbonate walls of karstic caves and carry dissolved nutrients that can be used by epilithic microbes, such as actinomycetes. As the microbial colonies grow, they trap and accumulate chemically-precipitated crystals in the organic matter-rich matrix formed that way. Perhaps these heterotrophic microbes, which produce CO2 as a waste product of respiration
Cellular respiration
Cellular respiration is the set of the metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate , and then release waste products. The reactions involved in respiration are catabolic reactions that involve...
and maybe organic acids, help to dissolve the carbonate as well. Of course, more research is needed to prove any current hypothesis.