MARSIAN, LUNAR AND METEORITES FROM ASTEROID VESTA
MARTIAN METEORITES
Martian meteorites came to Earth as a result of Mars colliding with large fragments of asteroids or comets. During the collision with the planet, these objects were destroyed and scattered at a speed sufficient to overcome the gravitational pull of the celestial body. All Martian meteorites show signs of impact from the enormous pressure of the blast wave from the destruction of an asteroid or comet.
IDENTIFICATION OF MARTIAN METEORITES
Confirming the origin of Martian meteorites requires microscopic examination and special chemical analyses. In 1976, NASA's Viking spacecraft landed on Mars and measured the composition of the planet's thin atmosphere, and in 1983, gases with the same composition were found in the Elephant Moraine 79001 meteorite. Thus, the origin of Martian meteorites was proven without having rock samples from Mars.
Cross-section of a Martian basaltic meteorite (shergottite). | Martian basaltic meteorite (shergottite), found near the Meharriz Oasis in Western Sahara in December 2022.
• The presence of the mineral maskelynite, formed from plagioclase under impact pressure, confirms the Martian origin of the meteorite.
• Martian meteorites contain minerals rich in iron oxide (magnetite, chromite, ilmenite), but do not contain iron in metallic form.
• Meteorites from Mars contain the mineral pyrrhotite, while ordinary iron meteorites have troilite.
• The minerals pyroxene and olivine have an iron-to-manganese ratio typical of Martian meteorites.
• Martian meteorites have a narrow range of oxygen isotope composition.
Martian meteorites belong to the achondrite group. There are three main types of Martian meteorites: shergottites (SHE = Shergottite), nakhlites (NAK = Nakhlite), and chassignites (CHA = Chassignite). Shergottite class meteorites have been found in various parts of the world, including Antarctica, Australia, Africa, and America.
Cross-section of a Martian basaltic meteorite (shergottite)
Martian basaltic meteorite (shergottite), Meharriz oasis in Western Sahara, December 2022
LUNAR METEORITES
As of December 31, 2024, 714 meteorites of lunar origin have been confirmed to have fallen on Earth. These are fragments from the Moon, ejected into space by collisions with asteroids or comets. The Moon has no atmosphere to protect it from meteoroids, and impacts on its surface are much more frequent and stronger compared to those on Earth, but only a small portion of the ejected rocks reach our planet. Most of them fly into space or enter the Sun's gravitational field. Rocks ejected from the Moon are captured by the gravitational field of Earth or the Sun and go into orbit around one of these bodies.
Ghadamis, lunar anorthosite, piece of lunar crust. Found in Libya. The meteorite is unique: almost identical to the samples from the Moon brought by the Apollo 16 mission
Ghadamis, lunar anorthosite, piece of lunar crust. Found in Libya. The meteorite is unique: almost identical to the samples from the Moon brought by the Apollo 16 mission
NWA 14188 is a rare lunar meteorite (basaltic breccia), discovered in Niger, Africa in 2021
Lunar meteorites are valuable to science as they provide information about the geology and history of the Moon without the need to send sample collection missions. They are identified through specific chemical and mineralogical characteristics that distinguish them from Earth rocks, as well as from meteorites from other celestial bodies.
The main types of lunar meteorites according to rock structure and mineral composition are:
• Lunar basalts: These are solidified lava and are relatively dark in color. They consist mainly of pyroxene and plagioclase minerals.
• Lunar breccias: These are fragments of different rocks cemented together as a result of impact events. They can contain both basaltic and anorthositic pieces.
• Anorthosites: They are light in color and composed primarily of the mineral plagioclase.
• Mixed lunar meteorites: They contain elements of both basalts and anort
Tisserlitine 001 Lunar feldspathic breccia with small metal grains, Mali-Algeria border, 2019
Polished plate from lunar meteorite NWA 11788 Feldspathic breccia, found in Mali in 2017
METEORITES FROM THE ASTEROID VESTA
Vesta is one of the largest objects in the Asteroid Belt of our Solar System (diameter 525 kilometers). It is the brightest asteroid visible to the naked eye from Earth, a remnant of a destroyed planet, as it still maintains a differentiated structure similar to the layers of Earth and other planets. Vesta is one of the most studied asteroids via space probes because it is one of the earliest formations in the Solar System and can provide information about the processes that led to the formation of other planets and asteroids.
Numerous fragments of Vesta were ejected from collisions billions of years ago, which left two enormous craters occupying part of the southern hemisphere of the asteroid. Debris from these events fell to Earth as Howardites, Eucrites, and Diogenites (HED) meteorites.
Iron meteorites form from the core; the boundary between the core and mantle forms stony-iron meteorites (pallasites); achondrites form from the mantle; various types of more or less altered chondrites form from the crust.
NWA 4664 achondrite (diogenite). Proven origin from Vesta. Found in 2006 in Algeria
NWA 15923 Eucrite. Discovered in 2022 in Mauritania. Classified as an achondrite (diogenite). Proven origin – Vesta
* The material uses photos from www.meteorites.bg and www.fossilera.com
