Broadcast 2684 Dr. David Stevenson

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Guest: Dr. David Stevenson; Topics:  Planetary science, Earth's Moon, Venus, Mars, interstellar travel, advanced propulsion, robotics vs. HSF.  Please direct all comments and questions regarding specific Space Show programs & guest(s) to the Space Show blog which is part of archived program on our website,   Comments and questions should be relevant to the specific Space Show program. Written Transcripts of Space Show programs are a violation of our copyright and are not permitted without prior written consent, even if for your own use. We do not permit the commercial use of Space Show programs or any part thereof, nor do we permit editing, YouTube clips, or clips placed on other private channels & websites. Space Show programs can be quoted, but the quote must be cited or referenced using the proper citation format. Contact The Space Show for further information. In addition, please remember that your Amazon purchases can help support The Space Show/OGLF. See

We welcomed Dr. Stevenson to The Space Show for a wide ranging planetary science discussion.  During the first segment of our nearly two hour program, we started out with my asking him questions about our Moon per his article published in the November 2014 issue of Physics Today, "Making the Moon." You can read and download this article at  One of the fun things that caught my attention in the article was Dr. Stevenson's discussion of the green cheese theory of the Moon.  I asked him about the origin of the green cheese theory, then we went on to more comprehensive discussions of other theories supporting the origin of our Moon.  I'm sure you will find this discussion and the article of great interest.

Additional topics about the Moon focused on scientific interest in the Moon, the Chinese plan to send astronauts to the Moon, lunar resources, privatization, lunar settlement, ISRU lunar plans. lunar seismology, the chemical structure of the Moon, impact basins and the Moon's geochemistry.

Dr. Stevenson received several email listener questions.  BJohn asked him for his most far out or weird idea.  Dr. Stevenson talked about his idea to probe the center of the Earth.  Sally wanted to know what the Chinese say they will do on the Moon.  Here, Dr. Stevenson said the reasons were not clear, he shared his experience in talking with Chinese lunar scientists when he was in China but that he got no detailed information for their lunar plans.

Next, we turned our attention to Venus.  We spent time discussing the lack of a moon for Venus and why.  This is actually a very good and comprehensive discussion about planet formation, Earth's formation and our Moon, and the likelihood that Venus did have a moon at one time, Neith, discovered centuries ago in 1672 by Giovanni Cassini.

Dr. Stevenson then compared the four terrestrial planets regarding moons, formation, planetary history, types of rocks and more.  Listen to what he had to say about Mercury, Venus, Earth and Mars.  He also said it was a travesty that we were not doing more missions and studying Venus more though there are some missions to Venus in the works.

In the second segment, listeners continued to ask questions about Venus, including a few by Matt wanting to know about Venus and magnetic fields  Matt also wanted to know about a Venus sample return mission.  You might be surprised by what Dr. Stevenson had to say about sample return missions.  Don't miss what he said about such a mission.

We talked about Mars and I asked if he thought Mars missions were in or out of balance with other planetary missions.  He said the balance was not too bad.  He also said the research for the  origin of life was interesting but that we don't know much about the origin of life.  Make sure you hear his comments on this subject. 

Interstellar challenges were also discussed.  A listener asked him about focusing more on Earth issues than space issues as a better value for the taxpayer.  The listener cited the recent string of large earthquakes as an example. 

Advanced propulsion topics came up but our guest said advanced propulsion projects were unlikely to pay off.  Don't miss what he had to say on this subject, including nuclear propulsion.  His comments included work on faster than light travel.  Exoplanets and telescope work were also the focus of our conversation.

For the rest of our program, we talked about the JUNO mission to Jupiter which arrives on July 4, 2016.  Juno is hoping to provide information about the origin and evolution of Jupiter.  Check out the Juno overview page at  Note that Dr. Stevenson is part of the Juno team.

Toward the end of our discussion, Victoria wanted to know about value for taxpayers with space programs given the typical American based on "man" in the street interviews for TV.  Dr. Stevenson had much to say about this, especially regarding teachers and the respect shown them.  He also said one has to start science education very early and maintain it.  Before the show ended, John from Ft. Worth called to talk some more about advanced propulsion.  The final question came from Alexander asking Dr. Stevenson to compare and contrast his students of today to those when he first started teaching.

Please post your comments in the comments section of this archived show on TSS website.  You can reach Dr. Stevenson through his Cal Tech faculty page or me.




Planetary science at its best!

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17 Apr 2016 Dr. David Stevenson
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