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Podcaster: Dr. Al Grauer

travelers-in-the-night

Title: Travelers in the Night Eps. 67E & 68E: Interplanetary Travelers – Lunar Meteorites & Rocks From Space Tell A Tale

Organization: Travelers in The Night

Link : Travelers in the Night ; @Nmcanopus

Description: Today’s 2 topics:

  • About one out of a thousand meteorites that you find on Earth started out on the Moon. They were given escape velocity from the Moon as a result of the impact of an asteroid or comet.
  • The history of our part of the Universe is written with a fine point in the space rocks which orbit our Sun. Some of them carry small grains of material from the cloud of gas and dust from which our solar system formed.

Bio: Dr. Al Grauer is currently an observing member of the Catalina Sky Survey Team at the University of Arizona.  This group has discovered nearly half of the Earth approaching objects known to exist. He received a PhD in Physics in 1971 and has been an observational Astronomer for 43 years. He retired as a University Professor after 39 years of interacting with students. He has conducted research projects using telescopes in Arizona, Chile, Australia, Hawaii, Louisiana, and Georgia with funding from NSF and NASA.

He is noted as Co-discoverer of comet P/2010 TO20 Linear-Grauer, Discoverer of comet C/2009 U5 Grauer and has asteroid 18871 Grauer named for him.

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Transcript:

67E: Interplanetary Travelers – Lunar Meteorites

One of the most amazing adventures in human history is the series of manned lunar landings that NASA made more than 45 years ago.  An extremely valuable scientific treasure are the lunar rocks and surface material that our astronauts brought back with them.

About one out of a thousand meteorites that you find on Earth started out on the Moon.  They were given escape velocity from the Moon as a result of the impact of an asteroid or comet. These lunar space rocks orbit the Sun or Earth and most of them eventually end on our planet.  

We are able to distinguish lunar meteorites from terrestrial rocks and meteorites from the asteroid belt by their chemical compositions and by comparing them with the lunar rocks the Apollo Astronauts brought back to Earth.

There are approximately 180 named lunar meteorites.  The largest one weighs about 30 lbs.  In fact, the largest 3, account for nearly 1/2 of the 150 lbs of lunar meteorites which have been found on the Earth’s surface.   

Lunar meteorites are very rare and so far none have been found in North America.  The best places to find them are the dry deserts in Africa and on the ice in Antarctica. They are scientifically important in that they sample the surface of the Moon in different places than did the Apollo Astronauts.

A lunar meteorite can be worth more than either the same mass of gold or diamonds. A lunar space rock with the mass of a US quarter could be worth between $4,500 and $225,000 depending on how rare it is perceived to be. 

68E: Rocks From Space Tell A Tale

The history of our part of the Universe is written with a fine point in the space rocks which orbit our Sun. Some of them carry small grains of material from the cloud of gas and dust from which our solar system formed.  They also carry clocks. Naturally occurring radio active potassium in space rocks decays into argon gas atoms which are trapped until the rock becomes molten. By measuring the potassium to argon ratio, Dr. Tim Swindle of the University of Arizona’s Lunar and Planetary Laboratory is able to determine the length of time since meteorites have solidified after an impact event. 

Scientists used a variety of methods to analyze fragments from the meteor whose impact injured nearly 1500 people in Russia in 2013.  Dr. Swindle points out that the evidence suggests that the asteroid parent of this object  was probably struck by high speed fragment which was ejected outward in the solar system from the impact which occurred when a Mars sized object struck the Earth. This event happened 4.45 billion years ago and left us with the Earth Moon system.  Space rocks from the asteroid and Moon forming fragment collision have orbited the Sun for billions of years.  One of them had collisions 30 million and 2 million years ago creating the Chelyabinsk meteoroid and put it on a path which caused it to collide with planet Earth.   

Dr. Swindle concludes from the evidence that the object which struck the Earth in February of 2013 had been banged around pretty hard a least 3 times before it finally exploded in our atmosphere.  

For Travelers in the Night this is Dr. Al Grauer.

End of podcast:

365 Days of Astronomy
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