Ask a Geologist: Meteorites...Linking meteorites to asteroids Ask A Geologist Series Meteorite...

Ask a Geologist:Meteorites

By: Prof. Sonia Tikoo-SchantzDepartment of GeophysicsStanford University

About MeSonia Tikoo-Schantz● I love traveling, history, and SPACE!● I am a huge sci-fi nerd

Fun fact: the actor who plays Commander Ben Sisko on Star Trek DS9 (Avery Brooks) graduated from Rutgers and has been a professor there!

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(PHOTO OF YOU)

Growing up

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I’m from Cape Girardeau, MO.

Voted “Most Likely to Become an Astronaut” in my graduating class.

College

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I went to college near Los Angeles

Did a summer engineering internship at the NASA Jet Propulsion Laboratory----> switched to Geology major

Grad School

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Did my doctoral studies at MIT, where I started studying meteorites and Moon rocks (Apollo samples).

with the Gibeon iron meteorite

With an Apollo 15 rock at NASA JSC

My work

image credits: Ben Weiss (MIT), artist Hernan Canellas

I use Apollo samples and meteorites to study magnetic fields in the solar system. I also work on the formation of impact craters by studying Earth rocks.

magnetism.stanford.edu

image credit: Alamy

What are meteorites?Objects originating from space that survived entering Earth’s atmosphere and fell to the ground.

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Spacecraft heat shield (ESA artist depiction)

fusion crust

Why study meteorites?Excluding Apollo(+), they’re basically the only space rocks we have!

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Artist rendering of JAXAHayabusa at asteroid Itokawa

nb: there have been a few successful robotic sample returns from the Moon/asteroids.

Why study meteorites?

They are collectively a treasure trove of information spanning 4.568 billion years

of solar system history:

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Meteorite falls

● 66 feet diameter (20 meters)● 40,000 mph (19 kilometers/second)● Exploded mid-air (airburst), energy of ½ a 1950s nuke

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Chelyabinsk, Russia (2013)

Chelyabinsk meteorite

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Recovered about 2,200 lbs (~1 metric ton) of material.

Wikipedia

theregister.co.uk

Meteorite finds

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Antarctica Atacama Desert Sahara/NW Africa

Rutgers EPS ProfessorJuliane Gross

Atacama meteorite hunting

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Where do they come from?

Ask A Geologist Seriesimage credit: Planetary Resources

Most are asteroids with Earth-crossing orbits.

Where do they come from?

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Also get them from the Moon and Mars, and other bodies (like comets).

Lunar Meteorite NWA 2727Image credit: M. Kayama, M. Sasaoka

Martian meteorite ALH84001 ©NASA

In the beginning...

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The solar nebula

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Chondrites (~90% of finds)

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Contain some of the earliest solid materials in the solar system!

Allende CAIs give age of solar system:~4.568 billion years ago

Growing planetesimals

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Jacob Simon

Gas and dust in the disk develop clumps that lead to forming larger bodies.

Gravitational collisions

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Once bodies get > 1 km (>~½ a mile), gravity can take over and things collide to form bigger planetesimals.

Don Dixon

Katamari Damacy video game

Eventually, some get big enough to attract stuff in their vicinity and grow rapidly.

Big planetesimals melt

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Segregate into dense metallic core and overlying silicate mantle.

Earth’s structure

Melting produced by heating from gravitational energy and radioactivity.

Iron meteorites

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The cores of bodies that underwent melting and differentiation.

Commonly used in jewelry, like:jewelrybyjohan

Iron meteorites

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Famous example: one produced Meteor Crater (Arizona)

● about ¾ of a mile across● 560 feet deep● 50,000 years old● Impactor was ~160 feet diameter

Achondrites

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The crusts of bodies that underwent melting and differentiation.

Stony-iron meteorites

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Meteorites tell us about the different types of bodies they come from

...as well as what we’re made out of!

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Annual Review in Earth and Planetary Sciences

Linking meteorites to each other

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Scientists use mineral similarities, as well as oxygen isotopes to link meteorites into groups.

Earth/Moon fall on the same line.

Linking meteorites to asteroids

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Meteorite Millbillillie vs. Asteroid 4 Vesta

Meteorites and asteroids are characterized by spectroscopy (how much light is reflected off a surface at different wavelengths).

Linking meteorites to asteroids

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Meteorite Millbillillie vs. Asteroid 4 VestaArtist rendering: Dawn spacecraft

Meteorites and life’s origins

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Rotelli et al. (2016)

Question Time!