Date: March 9, 2012

Title: As the Sun Burps

Podcaster: Bob Hirshon

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

Links: www.aaas.org

Description: When the Sun emits what is euphemistically called a “coronal mass ejection,” belching billions of tons of ionized plasma into space, satellites can fail and power grids can shut down on Earth, 150 km away. So imagine the effects on Mercury, just a third of the distance from the Sun, and defended by a much weaker magnetic field. In this podcast, Science Update host Bob Hirshon speaks with MESSENGER scientist Daniel Baker, Director of the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder, about how violent space weather is both an opportunity and a challenge for MESSENGER’s mission to Mercury.

Bio: Bob Hirshon is Senior Project Director at the American Association for the Advancement of Science (AAAS) and host of the daily radio show and podcast Science Update. Now in its 24th 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.

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.

Transcript:
Hirshon:

Welcome to the 365 Days of Astronomy Podcast. I’m Bob Hirshon, host of the AAAS radio show and podcast Science Update. And on the second Friday of each month, right here, I bring you news about the exploration of the inner solar system with a special emphasis on the planet Mercury. Why Mercury? Because right now, the MESSENGER spacecraft is in orbit around the planet. It’s the first spacecraft ever to orbit Mercury, and so I am covering that mission as it happens.

Before I get into this week’s topic, I notice that there aren’t a lot of comments on these podcasts. Maybe they are so fabulous that they leave you speechless? (awkward silence as Bob tries unsuccessfully to think of a witty segue back to point…) In any case, I am shamelessly going to pose a question that will help me produce future podcasts and that is this: what would you like to know about Mercury? In particular, what questions would you like me to ask the MESSENGER science team? Add them to the comments section below and I’ll go out to the Applied Physics Lab and over to Carnegie—that’s the two places where most of the team members work—and I’ll track down team members who can best answer your question. Then, I’ll use the responses for a future podcast.

And now back to our regularly scheduled show. Last month, I reported that MESSENGER has been given an additional year to conduct an extended mission, beginning March 17th. One member of the MESSENGER science team who is especially happy about this is Daniel Baker. He is Director of the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder. Baker specializes in space weather, or changes in plasma, magnetic fields and radiation in space, mostly caused by solar activity. Violent events on the Sun can result in large amounts of plasma—or magnetically charged, ionized gas – hurtling through space. This can affect communications satellites orbiting Earth, destabilize energy grids on Earth’s surface, and lead to extremely cool displays of aurora borealis and australis. Of course, with Mercury so close to the Sun, space weather there is much more intense. But Baker says that for the first part of the MESSENGER mission, the weather was pretty boring.

Baker:

The sun as many listeners may know, was in a very quiet state for about three years, from 2007 until 2010, when we had our first flybys of Mercury with MESSENGER. But then to our relief and also maybe to our consternation a bit, the sun has really been picking up in activity in recent months and about the time we went into orbit around Mercury with MESSENGER, the sun has been quite active indeed and so it’s bursting forth with lots of big events, lots of disturbances, solar flares and what we call coronal mass ejections, very large bursts of energy, maybe 10 billion tons of material that are expelled at very high speed from the sun.

Hirshon:

The uptick in solar activity makes Baker a lot busier and his job a lot more interesting.

Baker:

I’m sort of in the business of keeping an eye on the Sun and making sure that we in the project know what might be hitting us next, so we can be a little more ready for space weather.

Hirshon:

Mercury’s proximity to the Sun means that once solar activity is detected, there’s not much time to react.

Baker:

Often it’s just a few hours between the time the sun first reveals itself to be very active, lets say with a large solar flare, and the time that the coronal mass ejection that results can hit the planet. So sometimes we have to scramble quite a bit and be much more nimble and alert to be ready for space weather at Mercury than sort of the leisurely pace we can sometimes enjoy, where it may be two or three days before an event reaches the Earth.

Hirshon:

As a result, engineers designed MESSENGER to protect itself autonomously during solar events.

Baker:

We have to be pretty much ready for anything on a mission like MESSENGER and so the systems are pretty well able to take care of themselves, but quite often—as happened just this weekend, there was a disturbance on the sun that was quite a powerful coronal mass ejection. It happened that it wasn’t directed toward the earth, but it was pretty much a direct hit on Mercury and MESSENGER. And I’m aware that at least one of the instruments suffered what we call a “single event upset,” the memory on board the spacecraft in that instrument was affected and the instrument had to be shut down and restarted.

Hirshon:

So what is a “coronal mass ejection?” Baker explains.

Baker:

It’s a large blob of material, a large blob of what we call plasma: this is highly ionized gas, it also contains rather orderly and powerful magnetic fields. The energy content of this can be quite high: maybe 10 billion tons of material contained in this fast moving blob. It might be moving out at several million miles an hour away from the sun.

Hirshon:

Now, the MESSENGER team is not of one mind when it comes to these events. For the engineering team, tasked with keeping the spacecraft operating smoothly, every event is nail-biting time. Will it affect the instruments or other subsystems? And if so, will they react appropriately by powering down to protect themselves and then successfully power back up again? On the other hand, for the portion of the science team that is studying Mercury’s magnetic field, and the dynamics of its thin atmosphere, and the nature of its metal core, these violent solar events are cause for celebration.

Baker:

The effects as these blobs of material hit Mercury is that they can expel more material from the surface of the planet, can cause many of the species that we’re seeing, like sodium and calcium and other rather exotic species to be much more enhanced, they can greatly increase the activity within the magnetosphere of Mercury. And it’s for these reasons that we find it exciting and interesting that the sun has gotten more active. But on the other hand we don’t want it to be too active or too damaging to the spacecraft or to the operation of the systems. So we’re walking a line here between on the one hand wanting a more active sun so we see all these lively things happening with the Mercury system, but we don’t want it to be so lively that it knocks us out of commission entirely.

Hirshon:

Baker says that Mercury’s magnetic field has long been one of the planet’s central mysteries.

Baker:

Of course, we’ve been intrigued for decades, since the Mariner 10 days, that such a small and slowly rotating object as Mercury has an intrinsic magnetic field that extends well beyond the surface of the planet and really controls the plasmas I was mentioning before, the charged particles that swirl around the planet, and really acts also to sort of hold off the flow of the charged particles from the sun.

Hirshon:

And when it comes to better understanding Mercury’s magnetic field, things could not have gone better than they’ve gone so far for the MESSENGER mission.

Baker:

Well, we’ve been blessed in many senses, that is, when we flew by and in the very early stage of orbital part of the Mercury mission, the sun was very quiet, so we had a chance to see the system in its most quiescent state. Then the sun has begun, as I described before, this sort of picking up of activity over the past months. And now with the extended mission we’re going to be able to follow the active sun toward the peak of its activity cycle in 2013 and 2014. It’s hard to imagine a better phasing of the solar cycle with our cycle of exploration of Mercury, to be able to take it from its most basic and quiescent state to its most disturbed state. And as in most things, looking at a wide range of different activity levels tells you a lot more than just staying fixed in one little narrow interval of space and time.

Hirshon:

While Mercury’s magnetic field is much weaker than Earth’s, it is much stronger than that of any other planet in the inner solar system. As such, it gives scientists a touchstone to compare with Earth, to test theories about how magnetic fields operate.

Baker:

Yes, we see many of the same kinds of things happening at Mercury, but we also see many very different things because of its different size, the great speed with which things happen at Mercury. In many ways, Earth is like an elephant, and the metabolism rate of Mercury is like that of a mouse—it’s much faster, just a much more rapid pace. And so being able to compare these two creatures, the elephant-like Earth and the mouse-like Mercury magnetospheres has been quite fascinating.

Hirshon:

And as the only other rocky planet with a substantial magnetic field, Mercury holds clues to the origin of Earth and the rest of the inner solar system. MESSENGER scientists are hoping that the buildup in the sun’s violent activity will help provide answers to these questions, without knocking out the very instruments that capture the data they’ll need. Well, that’s all for today’s podcast. Don’t forget to add your comments and questions for future podcasts to this page. Thanks for listening. For the 365 Days of Astronomy podcast, I’m Bob Hirshon.

End of podcast:

365 Days of Astronomy
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