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UCLA Meteorite Lecture via Zoom Sunday June 14th


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This is an update on the lecture for this Sunday and the following month.

 

UCLA Meteorite Gallery Lecture Series

 The Meteorite Gallery is temporarily closed to the public until further notice.

 

Title: "Spherules in Sediment Deposits from Asteroid Impact Ejecta"

Lecturer: Dr. Frank Kyte, UCLA Cosmochemist.

When: 2:30 p.m. on Sunday, 14 June 2020.

Registration: https://ucla.zoom.us/meeting/register/tJ0ud-yppzkpH9zTgL43K75yP73wYub-w6ET

 

This talk will discuss formation of impact spherules and their occurrence in impact deposits ranging in age from 0.8 Ma (million years before present) to 3400 Ma.

 

When asteroids impact the Earth with cosmic velocities (about 20 km/sec) they release enormous amounts of kinetic energy. A large portion of this energy is transferred to the Earth's surface that results in seismic waves and excavation of a crater many times the asteroid's volume. Materials ejected from this crater are deposited mostly near the crater, but in large impacts the ejecta with the highest velocity can travel above the atmosphere and return as a global deposit. The famous dinosaur-killing impact at the K/Pg (a.k.a. KT) boundary produced a global deposit that was probably only a few mm thick. It is well known that this K/Pg layer has lots of iridium from the asteroid but its most distinctive characteristic on a macro level is that it is composed mainly of small spherical particles known as impact spherules. Impact spherules are a common feature of distal impact deposits (those deposited far from the impact site). Large impacts can melt significant amounts of crustal rocks in the impact crater, producing spherules around the crater. The highest velocity ejecta likely comes from a supercritical* "ejecta plume" composed of a mixture of crustal and asteroidal materials. As this ejecta plume expands, melt droplets will form, some condensing from a vapor, and these will solidify to form the silicate spherules common in impact deposits.

*supercritical link

 

Advance notice of the next lecture

Title: "DART (Double Asteroid Redirection Test): A Telescope Observer's Perspective"

Lecturer: Dr. Cristina Thomas, Northern Arizona University.
When: 2:30 p.m. on Sunday, 12 July 2020.

Registration:  https://ucla.zoom.us/meeting/register/tJwrde2vrz4tHtOUYDnw4xEBFtQrG6634bmy
 

DART is NASA's first planetary defense mission, which will test asteroid deflection by kinetic impactor. The spacecraft will impact the satellite of the binary near-Earth asteroid (65803) Didymos in fall 2022. I lead the DART team responsible for observing and understanding the orbit of the moon prior to and after impact. The observed orbit change will be how the team determines the effectiveness of the experiment.

We understand the orbit of the binary asteroid system using light curves, a measure of how the brightness of an object changes over time. When Didymos is close to Earth, the moon and the primary eclipse each other from the vantage point of our telescopes on the ground. Each eclipsing event causes a subtle dimming of the lightcurve known as a "mutual event". Observing these events enables us to observe the path of the satellite around the primary and predict the next mutual events. We observed the Didymos system in 2019 and have additional pre-impact observations planned for later in 2020 and early 2021. These observations will establish the state of the system before impact. We will perform similar observations in the period following the fall 2022 impact to determine the change in the satellite orbit. I will discuss how we understand the orbit of the satellite, results from our recent observations, and our future plans for observing the Didymos system.

 

Technical Support

Upon registration you should receive a confirmation email with login details (please check your Spam folder). If you need further instructions on how to join a meeting via Zoom click here or contact our Meteorite Manager, Natalia Campos, at ncampos@ucla.edu. This email will be especially monitored after 2 pm on Sunday.

 

Admission

Free and open to the public.

 

Contact

Email: meteorites@ucla.edu

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