Swirls, Rays, and other Moon Oddities with Dr. JA Grier

What are lunar swirls? Which side of the moon has more craters? Should we go back to the moon, and if so, why?

To find out, Dr. Charles Liu and co-host Alice Liu (she/they) welcome Dr. JA Grier (ee-em-eir), Senior Scientist and Senior Education and Communication Specialist at The Planetary Science Institute.

As always, though, we start off with the day’s joyfully cool cosmic thing: the publication of photos of a recently formed crater on the Moon, McGetchin Crater. According to Dr. Grier, new impact craters aren’t that rare, and certainly not on a geologic time scale. Ee describes how the moon is under constant bombardment by objects large and small.

For all its proximity to Earth, JA explains, there is much we don’t know about the moon. Chuck asks about some of the unsolved mysteries surrounding the moon, and Dr. Grier tells us about strange features on the lunar surface known as lunar swirls. Another mystery, one which JA wants to know more about, is why the bright rays around craters actually darken over time.

Next, we take a deep dive into crater formation on the moon. The impact is just the beginning, but it turns out the process is much more involved than that.

After our break, it’s time for our first audience question, from Natisha: “Why are there so many more craters on the dark side of the Moon than on the bright side?” First, Dr. Grier explains why “near side” and “far side” are better descriptions than “dark side” and “bright side,” and even that the far side is actually brighter colored due to the makeup of the surface. And when it comes to the number of craters, it’s pretty consistent on both sides.

Another surprise JA drops on us: areas of the lunar surface that look smooth are far from it, which had an impact on the Apollo lunar landings, including Apollo 11. The gang discusses the difficulties of landing on the moon, and on Mars, including the failure of the Mars Climate Orbiter mission, which crashed into the surface of Mars in September 1999. You’ll also hear about the challenges of methane rain for the future Dragonfly mission to Saturn’s moon Titan, how Martian dust impacted the solar panels on the Spirit rover, and the difficulty of communicating with missions on the far side of the Moon. As JA says, “Space is hard.”

For our next audience question, Joey asks, “Why should we spend so much money and time to go back to the Moon? Are there valuable natural resources there that we can mine?”

Dr. Grier talks about the importance of research, and how money spent on scientific exploration can have a direct impact on the science we need to improve our lives here on Earth. But when it comes to the idea of exploiting natural resources, whether on the Moon, Mars, or here at home, JA is a little less enthusiastic.

If you’d like to keep up with what Dr. JA Grier is doing, you can check out eir Staff Page on The Planetary Science Institute website here: https://www.psi.edu/staff/profile/ja-grier-2/

We hope you enjoy this episode of The LIUniverse, and, if you do, please support us on Patreon at https://www.patreon.com/theliuniverse.

Image Credits:

• McGetchin Crater. – Credit: NASA/GSFC/Intuitive Machines
• Image of the lunar swirl Reiner Gamma, cropped from Lunar Reconnaissance Orbiter WAC global mosaic. – Credit: NASA
• Asymmetrical ray system of the lunar crater Proclus (Apollo 15 image). – Credit: NASA
• Telescopic views of Copernicus Crater on the Moon. – Credit: NASA / Space Telescope Science Institute
• Rima Hadley, a sinuous rille, or long depression, on the Moon. The Apollo 15 crew photographed and sampled outcrops of rock on the near and far sides of the rille. – Credit: NASA
• NASA Apollo mission landings at six sites on the Moon between 1969 and 1972. – Credit: NASA Scientific Visualization Studio
• Artist concept of the Dragonfly mission on Saturn’s moon Titan. Dragonfly is scheduled to launch July 2028 and arrive in 2034. – Credit: NASA/Johns Hopkins APL/Steve Gribben
• Mars Exploration Rover Spirit's solar panels covered in dust in October 2007 on Mars. – Credit: NASA/JPL-Caltech/Cornell
• Lunar Image used on Title Card – Credit: Gregory H. Revera

CHAPTERS

00:00 Swirls, Rays and Other Moon Oddities with Dr. JA Grier

01:03 Introducing Dr. JA Grier, Planetary Scientist

02:15 New Lunar Crater, McGetchin Crater - Joyfully Cool Cosmic Thing

09:09 Lunar Mysteries: Lunar Swirls and Bright Rays Around Craters

12:43 In Space, No One Can Hear You Wooooo

15:57 Which Side of the Moon Has More Craters?

22:05 Space Is Hard

32:13 Why Should We Go Back to the Moon?

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