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Guest: Dr. Jay Melosh; Topics: Asteroids, comets, planetary defense, impact craters, dinosaurs & their death, planetary geology and geologic violence.
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We welcomed Dr. Jay Melosh to the show for this two segment 90 minute discussion regarding craters throughout the solar system, geologic violence, planetary exploration, habitat risks, Earth craters, the death of the dinosaurs and more. As we started the program, Dr. Melosh introduced us to the term geologic violence which would become common during our discussion. Additional topics discussed included impacts from plate tectonics and impact threats for the Earth, Moon, Mars and elsewhere in the solar system though he did say impacts were rate. Our guest also mentioned that there were 180 craters on Earth.
We talked about small meteors and larger ones with our guest providing us with size characteristics for these rocks. Dr. Melosh was asked if there were more impacts earlier in the solar system history than now. He mentioned the late heavy bombardment a crater count then and now. When asked if impacts were random for Earth, he mentioned our gravity field and explained the role of gravity in bringing in the rocks for impact.
Impact mitigation was discussed. Various methods were mentioned including the gravity tractor, kinetic impactors, and nuclear weapons. Time and distance to impact was important as you will hear with the more time available, the more and better the mitigation strategies. Impacts were mentioned for other possible locals for searching for life such as Mars, Titan and Europa plus Venus as it is of interest for cloud cities and more science research. Don't miss what he said about these various places in the solar system plus more about Earth's plate tectonics. Pluto was mentioned as it has proven to be full of surprises with mountains and glacial features. Upcoming missions were mentioned such as Mars 2020 and planned Mars sample return missions. When asked if our guest was concerned about bringing Mars samples back to Earth, he said he was more concerned without contaminating Mars. Don't miss this most interesting discussion as possibilities were mentioned for similarities with Earth and Mars life should one Mars life be confirmed. Dr. Melosh made it clear he was talking about microorganisms re Mars life or life elsewhere. Be sure to hear all of what he said on this topic.
Doug called to ask about a lunar base and microorganisms as a risk to an inflatable habitat structure. This too was an interesting discussion so don't miss what our guest about this risk and the hazard involved with inflatable structures. Before the first segment ended, BJohn sent in a question asking if there was a difference in an asteroid/meteor and comet crater. You might be surprised by what our guest said in response to BJohn's question.
In the second segment, we talked more about possible life being discovered on Mars, upcoming Mars science missions and the Chicxulub crater which was formed when the huge meteor struck the Earth and killed the dinosaurs some 60 million years ago. Dr. Melosh said the item was about 12 km in size. Later, when I asked if the crater being in the water dampened the impact, he said the water depth was maybe 50 meters so most of the meteor was clearly out of the water meaning the water would not have dampened the impact. Our guest spent some time describing the impact and what it did globally around the Earth which quickly killed all living creatures that could not go underground for protection. Don't miss this discussion and the likely scenario for the dinosaur extinction. He said it would have been very quick, perhaps within an hour or so of the impact.
Later in this segment, BJohn sent in a note wondering if gold or other ores could be found on the lunar surface. Our guest said no but explained why that was so. Don't miss his explanation. Before we ended the program, we talked about lunar water and the need to find, have, and use water throughout the solar system. Janet sent in the last dinosaur question wanting to know what Jay thought about using dinosaur DNA and bringing back to life a dinosaur. This too was a very interesting discussion s don't miss it. Our guest then talked about the GRAIL mission that he was part of and the location of lunar lava tubes that might prove OK for habitats.
Dr. Melosh told us about his impact website: www.purdue.edu/impactearth. Use the impact calculator to see what would happen if Earth got hit by an item that you describe and size out on the website. Before we ended, more was said about GRAIL and low density minerals and more on the Moon.
Please post your comments/questions for Dr. Melosh on our blog for this show. You can reach Dr. Melosh through me, the website above, or his Purdue faculty page.