Jun 28th: Exploring The Far Side & Martian Rolling Stones

By on June 28, 2020 in

Podcaster: Dr. Al Grauer


Title: Travelers in the Night Eps.553 & 554: Exploring The Far Side & Martian Rolling Stones

Organization: Travelers in The Night

Link : Travelers in the Night ; @Nmcanopus

Description: Today’s 2 topics:

  • The Apollo 8 astronauts were the first to view the Moon’s hidden side with the unaided eye.
  • Mars’s tiny moon Phobos has strange track-like groves crisscrossing it.

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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553 – Exploring The Far Side

The Earth and Moon, two unequal partners on a gravitational teeter-totter, have a center of mass which orbits the Sun once a year.  In this celestial dance Earth’s powerful gravity causes one side of the Moon to point towards us even as the Earth turns on its own axis of rotation once every 24 hours.  In 1959 the Soviet Luna 3 Probe was the first to photograph the 82% of the Moon we never see from Earth, while the Apollo 8 astronauts were the first to view the Moon’s hidden side with the unaided eye.  On Jan 3, 2019 the Chinese, Chang’e 4 [Chun uh 4]made a soft landing on the far side of the Moon where it is impossible to have direct radio communications with the Earth.  To keep in touch the  Chang’e 4’s communications are relayed to humans by a satellite in a halo orbit around the L2 Lagrangian point where the satellite can see both the Earth and the Moon’s far side.  

Both the Chang’e 4 and its Yutu rover companion are solar powered and also have radioisotopic heaters which allow them to survive the two week long lunar night when temperatures can reach 280 degrees below zero Fahrenheit.  The Yutu rover whose name means “Jade Rabbit” is making scientific measurements and sending back spectacular images of the virtually unexplored part of the Moon. In the meantime China is preparing Chang’e 5 which is designed to bring lunar samples back to Earth.  Stay Tuned.

554 – Martian Rolling Stones

Mars’s tiny moon Phobos is only 27 KM or about 17 miles in diameter.  Its surface is littered with huge boulders 160 feet in diameter and there are strange track like groves crisscrossing this small world.  Phobos’s surface gravity is 1,720 times smaller than on Earth so that if you weigh 180 lbs on Earth you would weigh only 1.67 ounces on Phobos.  Even stranger Phobos has a 6 mile diameter crater named Stickney which is nearly one third this tiny moon’s size.  

In an article in Planetary and Space Science astronomers Dr. Kenneth Ramsley and Dr. James Head explain how the impact which created the giant crater Stickney produced the grooves and huge boulders we see today. Their computer simulation produces bizarre images of boulders blasted loose by the Stickney’s impactor rolling around and around Phobos liberated by this small world’s micro-gravity. Their model shows that the boulder tracks produced right after the impact were likely crossed minutes to hours later by other boulders as they rolled around and around Phobos, like surface bound orbiting satellites.

 Imagine how strange and wonderful it would be to witness such an event.  When the impacting object hit it produced huge boulders, which held loosely by Phobos’s weak gravity, continued to roll around and around this tiny moon, bouncing and leaping over small surface depressions for hours after the impact.  Much later when all the dust and debris settled the impact left us with Mars’s moon Phobos as we see it today.

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

End of podcast:

365 Days of Astronomy

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About Al Grauer

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