When scientists first saw this structure in the images captured by the camera on the Dawn spacecraft, they could hardly believe their eyes: from the crater-covered surface of the Ceres dwarf planet rises a flat, steep, steeply sloping mountain 4,000 meters of height. It is the highest mountain in the dwarf planet almost a thousand kilometers in diameter and one of the most remarkable structures of the whole Solar System.
A study involving scientists from the German Aerospace Center (DLR) has already solved the mystery of how the Ahuna Mons, as the mountain is called, was formed, using gravity measurements and investigations of the geometric form of Ceres. A bubble made of a mixture of salt water, mud and rock rose from within the dwarf planet.
The bubble pushed the ice-rich crust upwards, and at a weak structural point the sludge, comprising hydrogenated salts and silicates, was pushed to the surface, solidified in the cold of space, in the absence of any atmosphere, and stacked to form a Mountain. Ahuna Mons is a huge mud volcano.
"In this region, the interior of Ceres is not solid and rigid, but mobile and at least partly fluid," explains Wladimir Neumann of the DLR Institute for Planetary Research in Berlin-Adlershof and the University of Munster.
The geophysicist contributed to the study, which has now been published in the journal Nature Geoscience. "This bubble that formed in the mantle of Ceres under Ahuna Mons is a mixture of salt water and rocky components."
Scientists describe a & # 39; cryocamera & # 39; – from the Greek word for ice, kryos – when speaking of a magma chamber on volcanoes on planets similar to the earth. Ceres is a dwarf planet on the outer edge of the asteroid belt. The largest body in this zone between Mars and Jupiter, populated by smaller planets, consists mainly of siliceous rocks, but also to a large extent of ice and presumably layers of water. Scientists are working on the assumption that as much as a quarter of Ceres's mass is ice or water – a proportion even greater than the Earth's freshwater and ice reserves.
The dwarf planet Ceres consists of up to a quarter of ice and water
After the asteroid Vesta, the space probe Dawn orbited the dwarf planet Ceres from March 6, 2015 until the end of October 2018, as the second destination of its mission, which began in 2007. Two identical cameras developed jointly by the Max Institute Planck for the Solar System The research and the DLR Institute for Planetary Research have photographed and mapped Ceres from different altitudes.
Many areas were captured stereoscopically so that scientists working in the field of planetary geodesy could calculate models of digital terrain that could be used to represent the surface topography of Ceres.
The interior of Ceres is not homogeneous, but rather the terminology of geologists, partly "differentiated", which means that after the formation of the celestial body, its components have become segregated and separated, at least to some extent. Components with a higher proportion of heavy elements, such as magnesium or iron, sank into the center of the body, while lighter components, such as rocks with a high content of aluminum silicate or water, rose.
Bubbles and domes are being created due to the heat that is still being generated today, four and a half billion years after the formation of Ceres, by the decomposition of radioactive elements. The presence of liquids influenced the internal formation differently from the usual rocky planets. As a result of their lower specific gravity compared to the surrounding materials, these bubbles rise and press against the crust from below. The domes a kilometer in height deform the crust and, once broken, the fluid material penetrates the surface.
An & # 39; iceberg & # 39; as high as Mont Blanc
When the Dawn mission reached Ceres, it captured extraordinary, almost snow-white surfaces on the planets, which we now know to be the result of a hydrogenated sodium carbonate or ammonium-containing clays, pale salts that are the result of "cryolecanic activity" . , i.e., by the eruption of aqueous solutions which immediately freeze at surface temperatures of about minus 100 degrees Celsius.
Ahuna Mons, in honor of the harvest festival of the Sumi Naga ethnic group in India, was created through this process in the recent geological past. With a base area of 20 kilometers in diameter and heights of 4,000 to 5,000 meters above the surrounding area, it has dimensions similar to Mont Blanc, the highest peak in the Alps.
"To explain the origin of Ahuna Mons, we had to use a new geophysical model that was specially adapted for Ceres and thus get to the hidden information behind the spacecraft data," explains Antonio Genova, of the University. of La Sapienza in Rome.
European Space Agency (ESA) spokeswoman Ottaviano Ruesch adds: "We are happy to know what process in the Ceres mantle, just below Ahuna Mons, was responsible for carrying material. was also somewhat "dubious" due to its volcano shape. "
Anomalies in the gravitational field gave the mud bubble inside
Scientists have interpreted the data to mean that Ceres' gravitational field was an anomaly, with the result that its gravitational pull, which was also exerted on the Dawn spacecraft orbiting Ceres, is somewhat larger.
As a result, the speed of the spacecraft accelerated a bit over this area, while slightly diminishing its orbit. This could be measured by the Doppler effect on radio communications with the space probe because the wavelengths were compressed or stretched, depending on the geometric constellation of the radio link.
"We looked more closely at this anomaly, and other modeling revealed that it should be a protuberance in Ceres' mantle," continues Ottaviano Ruesch. "The conclusion was obvious: the mixture of fluid substances and stones had reached the surface and accumulated in Ahuna Mons."
The activity of the cryolcanic is diffused in the External Solar System. Traces of this volcanic ice activity were discovered on the moons of Jupiter and Saturn, while some structures on Pluto also appear to have been formed in this way. Ceres is the first body in the asteroid belt where this type of extrusion was observed.
Unlike the moons of Jupiter, Europa and Ganymede, or the moon of Saturn, Enceladus, where water is compressed on the surface, the "magma" in the growing bubble of Ceres is composed of a mixture of saline water and mud or rock particles . Observations of the mineral composition of Ahuna Mons using an onboard spectrometer Dawn seem to confirm this finding.
The result of the study shows that large asteroids or dwarf planets made of siliceous rock and ice can form bubbles of salt water and rocky constituents inside it, which can rise to the surface and escape there. Scientists assume that this process can occur in these bodies for long periods of time, possibly billions of years, creating cryovolons on the surface.
DLR Institute for Planetary Research
Breaking Dawn at NASA
Asteroid and Comet Mission News, Science and Technology
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