METEORITES VS ASTEROIDS VS METEORS VS COMETS METEORITE IMPACTS IN HISTORY IMPORTANCE OF METEORITES FORMATION OF ASTEROIDS AND METEOROIDS CLASSIFICATION OF METEORITES

1. METEORITE
SUBHASMITA SAHU
2nd SEM
22GEOL007

2. CONTENTS
 INTRODUCTION
 METEORITES VS ASTEROIDS VS METEORS VS COMETS
 METEORITE IMPACTS IN HISTORY
 IMPORTANCE OF METEORITES
 FORMATION OF ASTEROIDS AND METEOROIDS
 CLASSIFICATION OF METEORITES
-STONY METEORITE
-IRON METEORITE
-STONY IRON METEORITE
-TEKTITES
-MARTIAN METEORITE
-LUNAR METEORITE
 FIND VS FALL
 HOW TO IDENTIFY A METEORITE
 METEOR IMPACT CRATERS IN INDIA

3. INTRODUCTION
 A meteorite is a solid piece of debris from an object,
such as a comet, asteroid or meteoroid that originates
in outer space and survives its passage through the
atmosphere to reach the surface of a planet or moon.
When the original object enters the atmosphere,
various factors such as friction, pressure, and chemical
interactions with the atmospheric gases cause it to heat
up and radiate energy. It then becomes a meteor and
forms a fireball also known as a shooting star
 Few meteorites are large enough to create
large impact craters.
 They may be derived from meteoroids(smaller) or
even asteroids(bigger).
 May also be derived from other planets such as mars
or even moon.
HOBA METEORITE IN
NAMIBIA

4. METEOROIDS VS ASTEROIDS VS METEORS VS COMETS
 Meteoroids- Object which orbits
around the sun or a collision course
with another planetary object.
 Meteors- Bright streak of light in the
sky due to burning of a planetary
object on entering the earth’s
atmosphere.
 Comet- An asteroid or meteoroids
which glow when close to the sun.
 Asteroid- It is bigger than a
meteoroid and orbits around the
sun.

5. METEORITE IMPACTS IN HISTORY
 Early Earth experienced many large meteor impacts that caused extensive
destruction. While most craters left by ancient impacts on Earth have been
erased by erosion and other geologic processes, the Moon’s craters are still
largely intact and visible. Today, we know of about 190 impact craters on
Earth.
 A very large asteroid impact 65 million years ago is thought to have
contributed to the extinction of about 75 percent of marine and land
animals on Earth at the time, including the dinosaurs. It created the 180-
mile-wide (300-kilometer-wide) Chicxulub Crater on the Yucatan Peninsula.
 One of the most intact impact craters is the Barringer Meteor Crater in
Arizona. It’s about 0.6 miles (1 kilometer) across and was formed by the
impact of a piece of iron-nickel metal approximately 164 feet (50 meters) in
diameter. It is only 50,000 years old and so well preserved that it has been
used to study impact processes.

6. IMPORTANCE OF METEORITES
 Provide direct information about the early condition.
 Provide direct information about the interior of the
planet i.e asteroids.
 Tells us about the planets/asteroids that have long
disappeared and constitute only ever source of
information.
 Age of formation of the solar system is based on age of
meteorites.
 Age of the earth is based on measurement of dating of
hundreds of meteorites.
 They are the oldest materials found in solar system.

7. FORMATION OF ASTEROIDS AND METEOROIDS
 Most asteroids and meteoroids are thought to originate from
the splintering of a handful of minor planets formed during
the infancy of our solar system a recent study shows.
 Most of the asteroids and meteroids are thought to be the
shattered remnants of planetesimals – bodies within the early
Sun's Heliosphere that never grew large enough to become
planets.
 The study, in Nature Astronomy, found at least 85 percent of a
sample of 200,000 asteroids in the inner Asteroid Belt (which
is the main source of meteoroids that make contact with the
earth) originate from just five ancient minor planets that were
decemated. The names of the ancient planets are Flora, Vesta,
Nysa, Polana and Eulalia.
 The ancient planetesimals are considered remnants from the
giant cloud of gas and dust that condensed to create the sun,
planets, and smaller objects some 4.5 to 5.0 billion years ago.
Today, most asteroids and meteoroids orbit the sun in the
tightly packed Asteroid Belt located between Mars and
Jupiter.

8. CLASSIFICATION OF METEORITES

9. STONY METEORITES/aerolites
 Chondrites. About 86% of meteorites are chondrites, which are named for the
small, round particles they contain. The small round particles, called chondrules,
chondrules, are embedded in molten grains of dust, grit and clay. The
chondrules are composed mostly of silicate minerals and olivine and pyroxene
pyroxene which is unique to the meteorites. Average composition is 40% olivine,
olivine, 30% pyroxene, 10-20% Fe-Ni, 10% plagioclase and 6% troilite. Certain
types of chondrites also contain small amounts of organic matter, including
amino acids, and pre-solar grains. Chondrites are typically about 4.55 billion
years old. Chondrites are some of the oldest and most primitive materials in the
the solar system. Chondrites are often considered to be "the building blocks of
of the planets".
 Achondrites. About 8% of the meteorites are achondrites (meaning they do not
contain chondrules) and are coarse grained. Some of these are similar to
terrestrial igneous silicate rocks and hence probably crystallized from the melt.
melt. Most achondrites are just ancient rocks, and are thought to represent the
the crustal material of the planetesimals. They are similar to basalts and gabbro.
gabbro. They are differentiated meteorites.

11. IRONMETEORITES/siderites
About 5% of meteorites that have fallen are iron meteorites composed of iron-
nickel alloys out of which Ni is 4.20% .Basically composed of two minerals-
kamacite(Ni poor) and Taenite(Ni rich). Lamellae are parallel to octahedral
faces. Lamellae are made up of kamacite and bordered by Taenite. Such
meteorites are called Octahedrites.
Hexahedrite- Dominated by Kamacite
STONY IRONMETEORITES/siderolites
Stony-iron meteorites constitute the remaining 1%. They have iron-nickel
metal and silicate mineral in equal proportions. They are of two types-
Pallasites and Mesosiderite. Pallasites have a continuous base of Ni-Fe and
enclose olivine grains of euhedral form. Mesosiderites have discontinuous
base and silicates are plagioclase and pyroxene with accessory olivine.

13. TEKTITE
 Tektites are small, pebble-like glassy objects
of Earth material that have been melted by
meteorite impact, splashed up into our
atmosphere, and fallen to Earth again under
gravity
 Made up of silica rich glass (75%SiO2) and
thus resembles obsidian but is different.
 Very low Mg and Na
 Usually occurs in areas where no volcanic
activity is known.
 Microtektites are tiny particles of tektite
dust found in deep sea sediment in the
Atlantic and Indian oceans.

14. MARTIAN METEORITE
 A Martian meteorite is a rock that formed on Mars was
ejected from the planet by an impact event, and traversed
interplanetary space before landing on Earth as a meteorite.
As of September 2020, 277 meteorites had been classified as
Martian, less than half a percent of the 72,000 meteorites
that have been classified. The largest complete, uncut
Martian meteorite, Taoudenni 002, was recovered in Mali in
early 2021. It weighs 14.5 kilograms (32 pounds) and is on
display at the Maine Mineral & Gem Museum.
 There are three groups of Martian meteorite: shergottites
,nakhlites and chassignites collectively known as SNC
meteorites.
 These meteorites are interpreted as Martian because they
have elemental and isotopic compositions that are similar
to rocks and atmospheric gases on mars, which have been
measured by orbiting spacecraft and rover.

15. LUNAR METEORITE
 Lunar meteorites are meteorites from the Moon. In other
words, they are rocks found on Earth that were ejected from
the Moon by the impact of an asteroid/meteoroid or possibly a
comet. Meteoroids strike the Moon every day. Any rock on the
lunar surface that is accelerated by the impact of a meteoroid
to lunar escape velocity will leave the Moon’s gravitational
influence. Most rocks ejected from the Moon are captured by
the gravitational field of either the Earth or the Sun and go into
orbit around these bodies. Over a period of a few years to tens
of thousands of years, those orbiting the Earth eventually fall to
Earth. Those in orbit around the Sun may also eventually strike
the Earth up to a few tens of millions of years after they were
launched from the Moon.
 The presence of cosmogenic nuclides is the ultimate test of
whether or not a rock is a meteorite. All lunar meteorites that
have been tested show evidence of cosmic-ray exposure.

16. METEORITE FIND VS METEORITE FALL
Only a small fraction of collected
meteorites have been observed to fall, 1.8%
for the whole world. “Observed” usually
means that a meteor was seen or heard and
the stone or stones causing the effects was
recovered shortly thereafter, usually within
a few days. Such meteorites are called “falls”
by meteoriticists. The other 98% are called
“finds” – someone found the meteorite but
the meteor was not observed.

18. HOW TO IDENTIFY A METEORITE
Meteorites have several properties that help distinguish them from
other rocks:
• Density: Meteorites are usually quite heavy for their size, since
contain metallic iron and dense minerals.
• Magnetic: Since most meteorites contain metallic iron, a magnet
often stick to them. For “stony” meteorites, a magnet might not
stick, but if you hang the magnet by a string, it will be attracted.
• Unusual shape: iron-nickel meteorites are rarely rounded. Instead,
they have an irregular shape with unusual pits like finger prints in
their surface called “regmaglypts.”
• Fusion crust: stony meteorites typically have a thin crust on their
surface where it melted as it passed through the atmosphere.

19. CONTINUING…
Meteorites do NOT have the following:
• Light-colored crystals: Quartz is a common, light-colored
crystal in Earth’s crust, but it is not found on other bodies
in the solar system.
• Bubbles: volcanic rocks or metallic slag on Earth often
bubbles or vesicles in them, but meteorites do not.
• Streak: if you scratch a meteorite on an unglazed ceramic
surface, it should not leave a streak. A dense rock that
leaves a black or red streak probably contains the iron
minerals magnetite or hematite, respectively, neither of
which are typically found in meteorites.

20. METEOR IMPACT CRATERS IN INDIA
OUT OF THE 190 METEORIC CRATORS FOUND ON THE EARTH, 3 ARE
PRESENT IN INDIA.
LONAR CRATER,
MAHARASHTRA
DHALA CRATER, MADHYA PRADESH
RAMGARH CRATER, RAJASTHAN

21. REFERENCES
1. JOHN D WINTER
2. Types of meteorites | Natural History
Museum (nhm.ac.uk)
3. Lunar meteorites | Some Meteorite
Information | Washington University in St.
Louis (wustl.edu)
4. Meteorite | Definition, Types, Identification,
& Facts | Britannica