IN THIS EPISODE (in order of appearance):Caleb Kinchlow
CALEB: 50 years of solar system exploration has brought us to the very edge of our solar system and back in, to the planet closest to our sun – Mercury.
DR. JAMES GREEN: Mercury, our closest planet to the sun, is bigger than our moon.
DR. RALPH MCNUTT You can see Mercury with the naked eye, it's one of the planets that has been known, of course, since antiquity, but you can't really see a lot of it.
DR. STAMATIOS KRIMIGIS Mercury was a challenge to begin with, because of how close it is to the sun, and the lack of atmosphere, and so on.
DR. JAMES GREEN Mariner 10 flew by Mercury, and so we got a look at it for the very first time.
DR. RALPH MCNUTT It kind of looked like the moon, uh, certainly no atmosphere, some volatiles apparently that were associated with it.
DR. STAMTIOS KRIMIGIS It did discover that it had a magnetic field, which was sort of totally unexpected.
DR. RALPH MCNUTT And everybody at the time had thought that, well, “Mercury is small, it would have cooled off, if it had had any sort of magnetic dynamo, it would have congealed a long time ago. And so the big question that was sort of left by Mariner 10 was in respect to the magnetic field. And it was kind of a, “Well, who ordered that?”
DR. NOAH PETRO: You know, fly-by missions showed us about half the surface of Mercury with images.
DR. RALPH MCNUTT We hadn't seen the other side with Mariner 10. So it remained one of the largest pieces of unexplored, un-imaged, close-up real estate in the entire solar system.
DR. JAMES GREEN: Very fascinating planet. And of course we wanted to go back and take a look at it.
DR. STAMATIOS KRIMIGIS: I always had a very strong desire to go back there.
DR. RALPH MCNUTT Well as we go further into the 90s, of course, the Discovery Program emerged and so a group of us, in March of 1996, said “Well, why don't we go to Mercury? How hard could that possibly be?” Actually, I think that's what I said, and of course I've learned a lot more since then, that it can be pretty hard. Well, MESSENGER, of course, is the first spacecraft to go into orbit around the planet Mercury. We ended up doing the orbit insertion burn in March of 2011, and we have been operating there since then. And it has just been a phenomenal success. We have been able to show that not only is there a magnetic dynamo there, but there's still largely a liquid core.
DR. LORI GLAZE There's an enormous amount of preserved vulcanism. And what the vulcanism tells you is a lot about the history of the interior of the planet.
DR. NOAH PETRO: We've got images covering the entire planet, topographic data, geochemical data. We're still left with lots of questions, Mercury is still a mysterious planet.
DR. JAMES GREEN: And in fact we now believe there's ices including water that's trapped in permanently shadowed craters in the North and South hemispheres, at the poles.
JOHNNY:Okay, why is it just being recognized now?
DR. NOAH PETRO: Again, though, we apply what we know about the Earth, the moon, how we think planets work, apply it to this really enigmatic place, and again, try to tell a story that is not only compelling but makes scientific sense.
DR. RALPH MCNUTT: It has been, I think, an incredible tour de force of actually going out to someplace we've only seen the first glimpse of, and really been able to – we haven't really rewritten the textbook yet, that's going to be coming up here in the next year or two, but we are going to be rewriting all the textbooks on Mercury.