Ask a Geologist: Meteorites By: Prof. Sonia Tikoo-Schantz Department of Geophysics Stanford University About Me

Sonia Tikoo-Schantz ● I love traveling, history, and SPACE! ● I am a huge sci-fi nerd (PHOTO Fun fact: the actor who plays Commander OF YOU) Ben Sisko on Star Trek DS9 (Avery Brooks) graduated from Rutgers and has been a professor there!

Ask A Geologist Series Growing up I’m from Cape Girardeau, MO.

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

Ask A Geologist Series College I went to college near Los Angeles

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

Ask A Geologist Series Did my doctoral studies at MIT, where I started studying meteorites Grad School and Moon rocks (Apollo samples).

with the Gibeon With an Apollo 15 iron meteorite rock at NASA JSC

Ask A Geologist Series My work magnetism.stanford.edu

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.

image credit: Alamy

image credits: Ben Weiss (MIT), artist Hernan Canellas What are meteorites? Objects originating from space that survived entering Earth’s atmosphere and fell to the ground.

fusion crust

Spacecraft heat shield (ESA artist depiction) Ask A Geologist Series Why study meteorites? Excluding Apollo(+), they’re basically the only space rocks we have!

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

Artist rendering of JAXA Hayabusa at asteroid Itokawa

Ask A Geologist Series Why study meteorites?

They are collectively a treasure trove of information spanning 4.568 billion years of solar system history:

Ask A Geologist Series Meteorite falls Chelyabinsk, Russia (2013)

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

Ask A Geologist Series Chelyabinsk meteorite

Wikipedia

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

Ask A Geologist Series Meteorite finds Antarctica Atacama Desert Sahara/NW Africa

Rutgers EPS Professor Juliane Gross

Ask A Geologist Series Atacama meteorite hunting

https://youtu.be/iNKMoxAYFv4 Ask A Geologist Series Where do they come from? Most are asteroids with Earth-crossing orbits.

image credit: Planetary Resources Ask A Geologist Series Where do they come from? Also get them from the Moon and Mars, and other bodies (like comets).

Martian meteorite ALH84001 ©NASA

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

image credit: Planetary Resources Ask A Geologist Series In the beginning...

Ask A Geologist Series The solar nebula

Ask A Geologist Series Chondrites (~90% of finds) Contain some of the earliest solid materials in the solar system!

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

Ask A Geologist Series Growing planetesimals

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

Jacob Simon Ask A Geologist Series Gravitational collisions Once bodies get > 1 km (>~½ a mile), gravity can take over and things collide to form bigger planetesimals. Eventually, some get big enough to attract stuff in their vicinity and grow rapidly.

Don Dixon

Katamari Damacy video game Ask A Geologist Series Big planetesimals melt Segregate into dense metallic core and overlying silicate mantle.

Melting produced by heating from gravitational energy and radioactivity.

Earth’s structure

Ask A Geologist Series Iron meteorites The cores of bodies that underwent melting and differentiation.

Commonly used in jewelry, like: jewelrybyjohan

Ask A Geologist Series Iron meteorites 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

Ask A Geologist Series Achondrites The crusts of bodies that underwent melting and differentiation.

Ask A Geologist Series Stony-iron meteorites

Ask A Geologist Series Meteorites tell us about the different types of bodies they come from

...as well as what we’re made out of!

Annual Review in Earth and Planetary Sciences Ask A Geologist Series Linking meteorites to each other

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

Earth/Moon fall on the same line.

Ask A Geologist Series Linking meteorites to asteroids Meteorites and asteroids are characterized by spectroscopy (how much light is reflected off a surface at different wavelengths).

Meteorite Millbillillie vs. Asteroid 4 Vesta

Ask A Geologist Series Linking meteorites to asteroids

Meteorite Millbillillie vs. Asteroid 4 Vesta Artist rendering: Dawn spacecraft

Ask A Geologist Series Meteorites and life’s origins

Rotelli et al. (2016)

Ask A Geologist Series Question Time!