Space weathering is the type of weathering that occurs to any object exposed to the harsh environment of outer space. Bodies without atmospheres (including the Moon, Mercury, the asteroids, comets, and most of the moons of other planets) take on many weathering processes: collisions of galactic cosmic rays and solar cosmic rays, irradiation, implantation, and sputtering from solar wind particles, and bombardment by different sizes of meteorites and micrometeorites. Space weathering is important because these processes affect the physical and optical properties of the surface of many planetary bodies. Therefore, it is critical to understand the effects of space weathering in order to properly interpret remotely sensed data. Much of our knowledge of the space weathering process comes from studies of the lunar samples returned by the Apollo program, particularly the lunar soils (or regolith). The constant flux of high energy particles and micrometeorites, along with larger meteorites, act to comminute, melt, sputter and vaporize components of the lunar soil. The first products of space weathering that were recognized in lunar soils were "agglutinates". These are created when micrometeorites melt a small amount of material, which incorporates surrounding glass and mineral fragments into a glass-welded aggregate ranging in size from a few micrometers to a few millimeters. Agglutinates are very common in lunar soil, accounting for as much as 60 to 70% of mature soils. These complex and irregularly-shaped particles appear black to the human eye, largely due to the presence of nanophase iron. Space weathering also produces surface-correlated products on individual soil grains, such as glass splashes; implanted hydrogen, helium and other gases; solar flare tracks; and accreted components, including nanophase iron. It wasn't until the 1990s that improved instruments, in particular transmission electron microscopes, and techniques allowed for the discovery of very thin (60-200 nm) patinas, or rims, which develop on individual lunar soil grains as a result of the redepositing of vapor from nearby micrometeorite impacts and the redeposition of material sputtered from nearby grains.

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Related publications (9)

Transport of dust across the Solar System: Constraints on the spatial origin of individual micrometeorites from cosmic-ray exposure

Reto Georg Trappitsch, Xuan Li

The origin of micrometeorites (MMs) from asteroids and comets is well-established, but the relative contribution from these two classes remains poorly resolved. Likewise, determining the precise origin of individual MMs is an open challenge. Here, cosmic-r ...
Royal Soc2024
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Related concepts (16)
Formation and evolution of the Solar System
The formation of the Solar System began about 4.6 billion years ago with the gravitational collapse of a small part of a giant molecular cloud. Most of the collapsing mass collected in the center, forming the Sun, while the rest flattened into a protoplanetary disk out of which the planets, moons, asteroids, and other small Solar System bodies formed. This model, known as the nebular hypothesis, was first developed in the 18th century by Emanuel Swedenborg, Immanuel Kant, and Pierre-Simon Laplace.
Ray system
A ray system comprises radial streaks of fine ejecta thrown out during the formation of an impact crater, looking somewhat like many thin spokes coming from the hub of a wheel. The rays may extend for lengths up to several times the diameter of their originating crater, and are often accompanied by small secondary craters formed by larger chunks of ejecta. Ray systems have been identified on the Moon, Earth (Kamil Crater), Mercury, and some moons of the outer planets.
Micrometeorite
A micrometeorite is a micrometeoroid that has survived entry through the Earth's atmosphere. Usually found on Earth's surface, micrometeorites differ from meteorites in that they are smaller in size, more abundant, and different in composition. The IAU officially defines meteorites as 30 micrometers to 1 meter; micrometeorites are the small end of the range (~submillimeter). They are a subset of cosmic dust, which also includes the smaller interplanetary dust particles (IDPs).
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