- Rare, ungrouped “other” Martian meteorites have unusual characteristics. The most famous Martian meteorite in the world, ALH 84001, for instance, is classified as an “orthopyroxenite” for its unique crystal silicate structure. ALH 84001 is less famous for its geology, however, than its possible biology—it may preserve fossils of primitive bacteria, providing evidence for life on Mars more than 4 billion years ago.
- Chassignites are named after the town where the first sample was found, Chassigny, Haute Marne, France. Very few chassignites have been identified, but all are rich in the mineral olivine. The olivine chemical structure leads scientists to think chassignites formed in the Martian mantle, not its crust. Chassignites are about 1.4 billion years old.
- Shergottites are named after the village where the first sample was found, Sherghati, Bihar, India. Shergottites are mafic rocks, meaning they are rich in magnesium and iron. They are the most abundant type of Martian meteorite, and also among the youngest. Scientists think shergottites may have formed as recently as 165 million years ago.
Astronomers and geologists have classified Martian meteorites into four major categories: shergottites, nakhlites, chassignites, and an oddball “other” or “unclassified” group.
- Nakhlites are named after the suburb where the first sample was found, Nakhla, Alexandria, Egypt. Nakhlites are volcanic rocks rich in the silicate mineral augite. They also provide evidence of abundant liquid water on Mars at some point in the planet’s history. Nakhlites are about 1.3 billion years old.
exactly or perfectly.
dry, barren rocks covered by an ice sheet that makes up most of the continent of Antarctica.
irregularly shaped planetary body, ranging from 6 meters (20 feet) to 933 kilometers (580 miles) in diameter, orbiting the sun between Mars and Jupiter.
person who studies space and the universe beyond Earth's atmosphere.
(singular: bacterium) single-celled organisms found in every ecosystem on Earth.
unproductive.
study of living things.
Martian meteorite composed largely of the mineral olivine. Also called olivine achondrite.
crash.
measure of the amount of a substance or grouping in a specific place.
radiation originating in outer space and consisting mostly of high-energy atomic nuclei.
type of mineral that is clear and, when viewed under a microscope, has a repeating pattern of atoms and molecules.
remains of something broken or destroyed; waste, or garbage.
area of land that receives no more than 25 centimeters (10 inches) of precipitation a year.
to get rid of or throw out.
chemical that cannot be separated into simpler substances.
to guess based on knowledge of the situation or object.
state of matter with no fixed shape that will fill any container uniformly. Gas molecules are in constant, random motion.
influence that a massive object extends around itself, in which another massive object would experience an attractive force.
having to do with igneous rocks that contain large amounts of iron and magnesium.
to determine the numeric value of something, often in comparison with something else, such as a determined standard value.
inorganic material that has a characteristic chemical composition and specific crystal structure.
Martian meteorite composed largely of the silicate mineral augite.
type of silicate mineral.
path of one object around a more massive object.
space beyond Earth's atmosphere.
small piece of material.
exact.
regular or able to be forecasted.
simple or crude.
transformation of an unstable atomic nucleus into a lighter one, in which radiation is released in the form of alpha particles, beta particles, gamma rays, and other particles. Also called radioactivity.
home or place where a person lives.
natural substance composed of solid mineral matter.
world's largest desert, in north Africa.
Martian meteorite composed mostly of mafic and ultramafic rocks.
rocky debris from space that enters Earth's atmosphere. Also called a meteor.
most common group of minerals, all of which include the elements silicon (Si) and oxygen (O).
the sun and the planets, asteroids, comets, and other bodies that orbit around it.
vehicle designed for travel outside Earth's atmosphere.
set of scientific instruments and tools launched from Earth to study the atmosphere and composition of space and other planets, moons, or celestial bodies.
process in which fragments of material (spall) are ejected from a larger body due to impact or stress.
atom with an unbalanced number of neutrons in its nucleus (isotope) that is radioactive, or decays by emitting particles from its nucleus. Also called a radionuclide.
having to do with volcanoes.
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