What is Space Weathering?

Space weathering is a general term for a series of changes that occur on the surface of celestial bodies exposed to the harsh space environment. Moons, Mercury, asteroids, comets and other celestial bodies without atmosphere, the surface layer will be illuminated by cosmic rays and solar radiation, solar wind particles bombardment, large and small meteorite and micro meteorite impact. The weathering process of space is an important factor affecting the physical and optical properties of celestial bodies. So understanding the role of weathering in space will help to interpret observations correctly.

Space weathering

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Space weathering is a general term for a series of changes that occur on the surface of celestial bodies exposed to the harsh space environment. Moon, mercury,

A lot of knowledge about weathering in space comes from

Non-atmospheric celestial bodies (such as the moon and asteroids) because of the lack of atmospheric protection, micron-sized solid particles (micrometeorites) can directly hit the surface of the celestial body and interact with surface matter; in addition, solar cosmic rays, galactic cosmic rays and Solar wind particles can also be injected onto the surface of the celestial body; under the influence of the above two effects, the spectrum of the celestial body will change greatly, often making the original spectrum darker (the spectral emissivity becomes lower) and red (the spectral albedo varies with Increase with increasing wavelength) and weaken the absorption band. ^[1]

Although the environment of the asteroid is

Mercury's environment is also very different from the moon. First, Mercury is hotter during the day than the moon (the surface temperature of the moon during the day is about 100 ° C, compared with 425 ° C for Mercury), and the night is colder, which will change the products of weathering in space. Second, because of its different position in the solar system, the impact speed of the micrometeor bodies that Mercury experiences is also greater than that on the moon. Under the combined influence of these factors, the efficiency of fusion or evaporation on Mercury will be much greater than that of the Moon. The melting rate per unit area of Mercury due to impact is expected to be 13.5 times that of the moon, and evaporation is 19.5 times. Mercury-like deposits of glued glass and steam generate at a higher rate than on the moon and spread faster on the surface.

The ultraviolet and visible spectrum of Mercury observed on Earth is generally linear and tilts toward the red end without absorption bands and iron-bound minerals, such as pyroxene. This means that either the surface of Mercury is either iron-free or has been weathered into nanophase iron. Surface weathering can explain why the color is reddish.