2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24
NASA has experimentally proved that numerous dark rocks on the surface of Jupiter's moon Europa may be sea salt from the subglacial ocean in its bowels. Scientists explain the unusual color of salt by ionizing radiation. The work is accepted for publication in Geophysical Research Letters and is available online.
According to the authors of the study, one can try to determine the composition of rocks on the surface of Europe taking into account two factors. First, the effects of intense radiation generated by Jupiter's powerful magnetic field. And, secondly, taking into account their characteristic color. According to scientists from NASA, the yellow-brown color of a number of areas on the surface of Europe was due to ordinary sea salt, which was subjected to hard ionizing radiation.
To confirm their hypothesis, planetary scientists conducted an experiment. They recreated in the laboratory the physicochemical conditions on the surface of Europa: temperature (minus 173 degrees Celsius), pressure, intense bombardment with a stream of electrons. A large number of different rocks and materials were placed in these conditions. After many hours of processing (equivalent in time to one century on the moon of Jupiter), their newly acquired color was compared to that of Europa's rocks.
To the surprise of the researchers, of all the selected salts, only samples of ordinary sodium chloride acquired after experimental exposure the characteristic yellow-brown color inherent in many stripes and spots on the surface of Europa. This was due to the fact that the so-called M and F color centers were formed in crystals during bombardment with electrons - point defects of the crystal lattice that absorb light in the spectral region in which there is no intrinsic absorption of the crystal. The color of the crystals changes depending on which region of the spectrum the color center has a maximum absorption. The yellow-brown color of the crystals occurs when the maximum falls on the blue part of the spectrum.
Salt crystals after exposure to hard ionizing radiation
Europa is the sixth moon of Jupiter. Its surface is formed from a layer of ice of many kilometers (from 80 to 170 kilometers according to various estimates). In 1979, Voyager obtained the first images of Europe showing numerous criss-crossing stripes and large areas ("freckles") of unknown dark rocks. Their color varied from yellow to dark brown. Since 1995, the Galileo spacecraft has received many detailed photographs of all these stripes, spots and other anomalies on Europa's surface. However, their nature remains the subject of constant debate among planetary scientists. Most researchers believe that dark rocks erupted from the depths of the satellite, but the lack of any data on their chemical composition does not provide reliable grounds for definite conclusions.
Due to the dissipation of tidal energy, the bowels of Europe are warmed up. According to the calculations of planetary scientists, at a depth of about 30 kilometers, ice should begin to melt, and a subsurface liquid ocean may exist under the outer ice crust on Europa. An important argument in favor of the presence of a subsurface ocean on Europa is its magnetic field, which is always oriented against the field of Jupiter. This means that it is created by electric currents induced in some deep layer of the satellite, which has good conductivity. The best possible candidate for this role is the salty ocean. The presence of salt in its waters may indicate the interaction of the liquid under-ice strata with deep layers of rocks. This is another argument in favor of the possibility of the existence of life on this satellite.
