Found particles knocked out by meteorites from the Moon – BBC

The atmosphere of the moon. For many of us, this phrase can cause a smile. Even at school, we know that our companion – a rocky body devoid of any kind was the gasbag. However, this is not quite true. Analysis of new data automatic station LADEE, conducted by NASA experts, makes a fresh look at the region near the Moon

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for the first time scientists have reflected during the flight of spacecraft “Apollo” program of the lunar atmosphere problem. Astronauts have repeatedly noted the unusual effects of light scattering near the border day and night side of the Moon. According to witnesses, it was like a “horizon glow” or “streams of light” above the surface. The effect was observed with the unlit side is during sunrise and sunset, both from the surface and lunar orbit.

Scattering of light on the Moon turned out to professionals as a complete surprise. Up to this point, scientists believed that our companion just does not have any atmosphere.

In fact, the moon is still massive enough body to keep some semblance of the atmosphere. It would be better to call it exosphere. It is the part of the Earth and the planets atmosphere, which is characterized by an extremely low concentration of atoms. At this density material particles being in exosphere virtually face each other. So if the particle acquires a greater speed than the second space for the body, it leaves the area of ​​attraction without any collisions. Such membranes are stretched by the planets at hundreds of thousands of kilometers. At the Earth’s exosphere – this outermost region of the atmosphere. But the moon is nothing but the exosphere, not at all. Moon atmosphere consists essentially of ionized atoms of hydrogen, helium, neon and argon. However, in 1991, the research team from Boston University was discovered sodium tail, extending to 15-20 lunar diameters in the direction opposite the Sun

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it turns out that the gas shell of the moon is still there, but it is not enough to explain the observed light scattering effects. The density of the atmosphere at the surface of the moon is approximately the same as that of the Earth’s atmosphere at an altitude of the International Space Station. Although due to the deceleration of the atmosphere of the station has to regularly “lift”, such a density can be considered almost a vacuum.

It turned out that glow lunar sunrise and sunset is due to dust, which rises to a height of several kilometers and scatters light . Initially, there are two versions of how moondust can rise so high. According to the first, all the fault of meteorites constantly bombarding the lunar surface. In another version, the dust rises under the action of the sun and ultraviolet radiation gamma. Under the influence of the sun’s rays, electrons knocked out of atoms and molecules, dust particles, resulting in it acquires a positive charge and is ejected at high altitude.

The effect can be enhanced when the Moon passes a magnetic tail of the Earth .

In order to study the properties of the lunar exosphere in 2013 and the automatic station was launched LADEE (Lunar Atmosphere and Dust Environment Explorer – «Explorer lunar atmosphere and dust environment”). During the construction of the spacecraft main priority it was cheap. In fact, on LADEE installed only scientific instruments, which do not need to be developed from scratch, which is very unusual for NASA space missions. spacecraft and interesting design itself. Engineers involved in designing LADEE, developed a system of separate carbon fiber modules, which can be combined as a designer. This technology will further allow to quickly and cheaply create automatic stations for a variety of space missions, collecting various units into a single structure. Modular scheme even allows you to create landers. Initially, the budget of the mission was to make a very modest $ 80 million. But in fact, it rose to $ 280 million.

Despite the fact that LADEE not established a fundamentally new devices, all used equipment has been upgraded and improved. Scientific equipment located on the front side of the body. Spectrometer UV and visible ranges (UVS) studied the properties of lunar dust and the exosphere, observing the scattering of light at sunrise and sunset over the edge of the lunar disk. Neutral Mass Spectrometer (NMS) studied the composition of the lunar atmosphere.

By the way, the NMS is set to analogue Cassini apparatus, which still continues to study Saturn. Dust sensor LDEX engaged calculation of the masses of dust particles.

But in addition to studying the exosphere of the moon before the machine was put another important purpose – to check the possibility of space laser communication. The fact that modern radio communication has severe restrictions on the data rate. For example, the transmission rate of the radio link from Mars to Earth is less than 2 Mbit / s. As the laser beam information could be transmitted much faster. During the experiment LLSD (Lunar Laser Communication Demonstration) from the spacecraft to Earth failed to transmit information at speeds in record 622 Mbit / s, more than six times faster than the fastest cosmic radio

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The mission LADEE ended April 17, 2014, when the automatic machine at a speed of 5800 km / h Planned collided with the lunar surface. By the time the fuel supply was almost exhausted, and leave the uncontrolled station in lunar orbit, it would be risky for future missions. However, the data processing continues to this day. After examining data LADEE, NASA experts have published in the journal Nature Geoscience work, bringing a new look to the space around airless bodies.

Scientists interested in the dependence of the dust envelope around the moon from external influences. In this paper, they compared the results of spectral observations of the exosphere particles at different times. First – this is January 4, 2014, when there was the peak of the meteor shower Quadrantids on the lunar surface is constantly falling meteorites are small. Second – it is 10 April of the same year, when no active meteor showers were not. The researchers found significant differences in the readings of scientific instruments for these dates.

It turned out that the number of light-scattering particles significantly increased at the moment of the lunar bombing. By comparing the simulated and experimental data, scientists have estimated the size of the scattering particles of dust, which was surprisingly small, not exceeding 20-30 nm. The scientists also determined the number of scattering particles in the line of sight at the edge of the lunar disk.

The small size of the grains the researchers explain the fact that the impact of a meteorite on the surface of the fine particles acquire high speeds and climb a greater height and are longer in flight.

The authors point out that this is the first confirmation of the variability of the lunar exosphere, which contains a huge amount of dust particles smaller than 20 nm. They also point out that such dust shell can have many bodies of the solar system, devoid of atmosphere that must be considered when planning future missions to the Moon and asteroids.