Date: December 10th, 2012

Title: Ice and Organic Goo On Mercury

Podcaster: Bob Hirshon

Organization: American Association for the Advancement of Science (AAAS)

Link: www.aaas.org

Description: In a series of papers published in Science, scientists from the MESSENGER Mission to Planet Mercury announced the discovery of water ice and organic volatile compounds on the surface of Mercury.  AAAS Science Update host Bob Hirshon spoke with key scientists on the team at a NASA press conference.

Bio: Bob Hirshon is Program Director for Technology and Learning at the American Association for the Advancement of Science (AAAS) and host of the daily radio show and podcast Science Update. Now in its 25th year, Science Update is heard on over 300 commercial stations nationwide. Hirshon also heads up Kinetic City, including the Peabody Award winning children’s radio drama, McGraw-Hill book series and Codie Award winning website and education program. He oversees the Science NetLinks project for K-12 science teachers, part of the Verizon Foundation Thinkfinity partnership. Hirshon is a Computerworld/ Smithsonian Hero for a New Millennium laureate.

Today’s Sponsor: This episode of 365 Days of Astronomy is sponsored by The Education and Outreach team for the MESSENGER mission to planet Mercury. Follow the mission as the spacecraft helps to unlock the secrets of the inner solar system at www.messenger-education.org

Additional sponsorship for this episode of 365 days of astronomy was provided by Clear Skies Observing Guides, a Modern Day Celestial Handbook. www.clearskies.eu..Clear skies observing guides, or CSOG, is a new concept in visual amateur astronomy. The observing guides contain thousands of objects to observe through amateur telescopes, with matching tours for GOTO telescopes and matching AstroPlanner plan-files. CSOG allows you to target deep-sky objects and carbon stars you never observed before, night after night. Wishing astronomers around the world: Clear skies..! ”

Transcript:

Hirshon:
Welcome to the 365 Days of Astronomy podcast. I’m Bob Hirshon, and I am reporting from NASA Headquarters in Washington, DC. This is the site of a press conference on the MESSENGER Mission to Planet Mercury and they’re going to make a big announcement here—or a few announcements, there are several scientists reporting. And it’s being reported in Science magazine today. This is Thursday, November 29th. So we’re going to go and see what it’s all about.

[Scientists on podium at press conference for a few seconds]

So, Sean Solomon, the project lead on the MESSENGER mission to planet Mercury has announced the discovery of water ice ond a dark material thought to be volatile organic compounds associated with the water on Mercury, up in the craters in the polar regions, in this case the north polar regions.

Seeing if the reflective patches that telescopes have already seen at Mercury’s poles—seeing if those are water is one of the questions that MESSENGER was originally sent to answer, so the water isn’t a huge surprise, but the organics sure are. And right now, David Paige from UCLA is talking about those volatile organics. He mentioned that they may be the same sort of material that gave rise to life on Earth. And these Mercury deposits could be the only place where those original materials exist. Certainly the only planet.

So once the presentations are over, I’m going to try to talk with some of the scientists directly.

[In press conference area after formal discussions]

First, could you say your name and title?

Lawrence:
David Lawrence, Senior Scientist at APL.

Hirshon:

And what was your role in finding these water and volatiles?

Lawrence:

I did the data analysis for the neutron spectrometer, which measures hydrogen concentrations at Mercury’s north pole.
Hirshon:

Okay, and as I understand it, you’re using something that’s basically already there: cosmic radiation—

Lawrence:
Cosmic rays—

Hirshon:

And it flies all over the place and, luckily, when it hits a hydrogen atom, it is something that you can notice. Or you can notice that lack—

Lawrence:

Notice the lack, the lack of neutrons is the signature of a lot of hydrogen, yeah.

Hirshon:

So if it’s not there, hydrogen is there.

Lawrence:

Correct.

Hirshon:

And knowing there’s hydrogen there, how do you know there’s water there?

Lawrence:

Well, that’s an inference, and for this measurement, we can measure how much hydrogen matches what we would expect if you fill these radar bright regions with water ice. And when the two match up quantitatively, it’s a pretty sure match that the hydrogen you measure is in the form of water ice. And then you put all the other information together, the radar data, the temperature, the MLA – they’re all pointing toward water ice.

Hirshon:

And just for a lay audience, is there any way to explain why hydrogen is the one that stops (cosmic rays), why not boron, why not anything else?

Lawrence:
It’s basically billiard balls. Think of billiard balls as being hydrogen and protons, and think of bowling balls as being all the other atoms. So let’s say you have a room full of bowling balls and you have a billiard ball in your hand and you toss it in the room—get out of the way, it’ll knock you in the head. It’s bouncing back very fast. But if you take the cue ball and you hit it dead on with a billiard ball, it dies very quickly. What it is, the technical term is it loses its momentum very—it has very good momentum transfer, because they’re the same mass.

Hirshon:

And the cosmic rays are—

Lawrence:

And the cosmic rays are protons, and what they do is they break apart all the neutrons from the atomic nuclei, and they’re just bouncing around like billiard balls bouncing around bowling balls. And occasionally, when you find hydrogen atoms, they die, they lose their energy very quickly. It’s really that simple.

Hirshon:

If you could say your name and title…

Neumann:

I’m Gregory Neumann, at NASA Goddard Space Flight Center and I’m an MLA Instrument Scientist and a geophysicist.

Hirshon:

Okay, and…?

Paige:

I’m David Paige, I’m a professor of planetary science at UCLA, and I’m a MESSENGER Participating Scientist.

Hirshon:

And how deep do you think the water is?

Neumann:

Several meters, but the altimeter could tell you if it were more than that, because we would see, and we have not yet seen, traces of ice berg processes. That is, the surface doesn’t seem to have been built up.

Hirshon:

And this was a surprise, I was expecting the water, but what about volatiles and how did you find those?

Neumann:

Well, I wasn’t expecting those, but we started seeing them immediately, as soon as we went into orbit. And it was Dave who told us, “hey, I have an idea.”

Hirshon:

And what was your idea and why?

Neumann:

Well, we know two things about the stuff: it’s really dark—like about the same reflectance as coal—and also that it tends to disappear when you get it too hot, like at about the boiling point of water. And the only material in the solar system that fits those two descriptions is this dark organic material that we find covering comets and also other icy bodies in the outer solar system.

Hirshon:

And isn’t it crazy—I was shocked—that you find the brightest stuff and darkest stuff, and those are the most interesting and the most detectable. It just seems there’s so much, I don’t know, serendipity about it.

Paige:

And to just see this ice that we’ve been hypothesizing about just right there in the data is just Whoa, that’s really exciting.

Hirshon:

It’s almost better than – I mean, most people say you know something, or see it, by looking at it, but you guys are actually making models and actually seeing every model lay on top of every other model perfectly, or almost perfectly. And that’s almost more exciting and more convincing.

Paige:

Right, we see it AND understand it, which is doubly good.

Hirshon:

Here’s Sean Solomon, he’s the principal investigator and lead scientist on MESSENGER.

[to Solomon]

Hey, congratulations. You got a minute?

Solomon:

Okay.

Hirshon:

Why is it especially interesting and illuminating to find this on Mercury? I mean, we know there’s water all over the solar system, especially way out in the outer reaches. Why is it particularly interesting and perhaps instructive to find it on Mercury?

Solomon:

The reason is that Mercury has an ability to store this material, that is no doubt delivered to all the other inner planets. But Mercury has these very stable cold freezers at the north and south pole.

If you delivered volatiles to the Earth, it would just be a drop in the ocean. If you delivered volatiles to Mars or Venus, the event would pretty soon be lost to all of the more dynamic geological and atmospheric processes that happen on those two bodies. But Mercury has these cold recorders of the arrival of volatile materials. And gives us, therefore, a window into the time scale, into the spatial scale for delivery of water, for delivery of organic material, for delivery of other volatile materials, to bodies for which that record was lost. And the fact that we see it on the planet closest to the Sun is astounding enough, but the fact that it also informs our ability to work out the history of volatile delivery on Earth and Mars and Venus is very special.

Hirshon:

People hear organics, they water, they think “life.” And I know you’re not expecting to find life there, but you said it does tell you something, perhaps,  about the origins of life in the solar system.

Sean:
There are many steps between the delivery of simple molecules and the emergence of life on the Earth. And most of those steps are completely lost from the geological and biological record.  We can only speculate, we can do laboratory experiments, we can look at meteorites, we can search for the possibility of organic materials on Mars, as the Mars Science Laboratory Curiosity is doing now. But Mercury gives us another lever arm on these early steps in the assembly of the building blocks of life.  And Mercury probably also saw some early organic chemistry. In the case of Mercury, it was driven by the radiation and thermal environment of the planet closest to the Sun, but it still gives us clues into what kinds of organic materials might have been assembled in a planetary setting once the basic building blocks had been delivered.

Hirshon:

And does it confirm ideas that you only up to now could have just surmised? Does it tell you something you can’t learn from other phenomena that might be observable?

Sean:

Well, what’s different, I mean, it suggests that material from the outer solar system has been delivered to the inner solar system and gathered up by the inner planets and we had reason to believe that has been the case, and we can go out with spacecraft to the outer solar system and look at what materials are there.  But to have a direct handle for Mercury on the end product of that delivery at one of the most extreme environments in the inner solar system I think gives us an anchor to a lot of ideas for how much material has been delivered in that manner, how rapidly that material has been delivered over time over the history of the solar system. So it’s a very important new set of observations that gives us a constraint from a part of the solar system where we had no record before.

Hirshon:

Great, thanks!

So that about wraps it up from here at NASA headquarters in Washington, DC. For the 365 Days of Astronomy Podcast, I’m Bob Hirshon.

End of podcast:

365 Days of Astronomy
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