Scientists have created a "portrait" of Mercury. / September 8, 2010 /
NASA scientists from the Centre for Space Flight by R. Goddard seriously studying such planets as Mercury. Solar wind and the many meteorites make exosphere of the planet is constantly changing. This variability can be a lot to tell astronomers.
Small Mercury undergoing major disaster: a powerful solar wind and high-speed micrometeorites. The thin gaseous envelope of the planet, exosphere, slightly denser than the vacuum and can not protect the planet. It is constantly changing and filled with sodium, potassium, calcium, magnesium and other elements that are exempt from the soil of Mercury the solar wind. Rich variety of elements, exosphere actively responds to sunlight, wind and magnetic field, and its amazing variation can tell a lot astronomers.
Summing up the data obtained during the mission space probe Messenger, NASA scientists from the Centre for Space Flight. R. Goddard were «portrait» of Mercury and presented it to the public in the September edition of Icarus.
How to simulate the planet Mercury? None of the spacecraft does not sit on its surface, so astronomers have to look for indirect methods of research. For example, to study the moon. Like Mercury, the Moon has a similar process of mass transfer from the surface into an extremely thin exosphere. When scientists want to find out what the soil can lead to increased concentrations of sodium and potassium in Mercurys exosphere, they studied samples of lunar soil brought by the 16 th Soviet apparatus series «Moon».
Study of the exosphere. Atoms and molecules in Earths atmosphere make sudden movements and all the while facing each other, but in the exosphere of Mercury is rather the exception they often fall to the surface than the «find» each other. Observations from ground-based telescopes and MESSENGER-and show that sodium, calcium and magnesium, are exempt from the soil as a result of various processes and behave in the exosphere in different ways.
Mysteries of sodium. New models have demonstrated amazing strength, releasing huge amounts of sodium. Researchers believe that the main factor influencing this process is the impact of charged particles on the surface of the planet, which is free of sodium in a process called ion sputtering (bombing of the individual particles, which have more energy than the atom object, which object is sprayed) . But it turned out that the main factor is the photostimulated desorption (separation of the absorbed substance as a result of the vibrational motion), reinforced by the blows of the ions. Sodium atoms, pushed by the solar wind, stretched into a huge tail, which lags behind the Mercury and pulled like the tail of a comet. As it is possible to judge the impact of solar radiation on the exosphere. After calculations also revealed that 15% of the observed sodium emission associated with impacts of micrometeorites. Simulation of the magnetosphere highest concentration of sodium observed in the North and South poles of Mercury, but during the first MESSENGER-span and found that in the Northern Hemisphere release of sodium to 30% more. Simulation of the magnetosphere of Mercury reveals that the reason is that near the North Pole proton bombardment of the surface is four times more intense. This is due to the fact that the solar wind presses on the planets magnetic field at an angle and bends it.
Impacts of charged particles near the North Pole is actively working with the photostimulated desorption, and it is rapidly depleting stocks of sodium on the surface. On the extraction of sodium from the deeper layers of the soil requires more time, that takes some time, but charged particles significantly accelerate this process.
Intense sunlight can turn released from the soil material in the positive ions (photoionization). Some of these ions can travel on the «conveyor belt» around the world to make half or a few turns. It is possible that this hypothetical conveyor can also create magnetic anomalies such as «failures» in the magnetic field of Mercury, MESSENGER found that on both sides of the planet. While not known, what is their cause and whether the ions in the «pipeline» to create such powerful distortions of the field.
Mystery of magnesium Spacecraft Messenger first to find magnesium in the exosphere of Mercury. Astronomers expect that the highest concentration of magnesium on the surface of planets and gradually declines as the climb. Instead, Messenger discovered a large concentration of magnesium over the North Pole, where he remained for some time, its density, and then suddenly the concentration has fallen sharply. More such phenomenon was not observed, and scientists can not explain it. The researchers also note that the temperature of the magnesium can reach tens of thousands of degrees, significantly higher than the surface temperature (about 400 degrees Celsius). The processes occurring on the surface of the planet, probably can not cause the appearance of this red-hot magnesium, but the true nature of this phenomenon is still unknown.
Perhaps many mysteries of Mercury will be solved after 18 March 2011 Messenger will orbit the nearest neighbor of the Sun.