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Unmanned > Inner Solar System and the Sun > Mercury > Messenger

there will be a MESSENGER Update teleconference today (July 3rd, 2008) at 2:00pm EDT

Below is the link for live audio streaming...
NASA to Reveal New Discoveries from Mercury
NASA will host a media teleconference Thursday, July 3, at 2 p.m. EDT, to discuss analysis of data from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft's flyby of Mercury earlier this year.

The spacecraft is the first designed to orbit the planet closest to the Sun. It flew past Mercury on Jan. 14, 2008, and made the first up-close measurements since Mariner 10's final flyby in 1975.

Analyses of the data show volcanoes were involved in the formation of plains. The data also suggest the planet's magnetic field is actively produced in its core. In addition, the mission has provided the first look at the chemical composition of Mercury's surface. The results will be reported in a series of 11 papers published July 4 in a special section of Science magazine.

The teleconference participants are:
- Marilyn Lindstrom, program scientist, NASA Headquarters
- Sean Solomon, principal investigator, Carnegie Institution of Washington
- James W. Head III, professor of geological sciences, Brown University, Providence, R.I.
- William McClintock, senior research associate, Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder
- Thomas H. Zurbuchen, associate professor, Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor

Reporters may access the embargoed science press package materials by registering with EurekAlert! at and e-mailing to expedite their registration. Once registered, they may log in directly at:

To participate in the teleconference, reporters in the United States should call 1-888-455-3616 and use the passcode "messenger." International reporters should call 1-517-623-4705. Audio of the teleconference will be streamed live at:

When the briefing begins, related images will be available at:


The MESSENGER topic had got huge so I thought it was time for a new thread.

Here's the links for the press graphics:

Main talks are over. Most of it is pretty similar to the last press briefing; I'd say the most surprising and interesting results are from FIPS, who think they found water(!?!) in the exosphere...

Thanks Emily....

I was not sure which thread to put the press briefing announcement.

Unable to listen in myself....

From the MESSENGER Mission News..

"The magnetosphere is full of many ionic species, both atomic and molecular and in a variety of charge states. What is in some sense a ‘Mercury plasma nebula’ is far richer in complexity and makeup than the Io plasma torus in the Jupiter system. The abundances of silicon, sodium, and sulfur relative to oxygen in the solar wind are too low, and their charge states — ionization — are too high to account for the abundances we measured, so there is no doubt that this material came from the planet’s surface. This observation means that this flyby got the first-ever look at surface composition.”

Plus the spectra showing water group ions... neat! See slide 5.4 of the presentation materials

Though I draw a complete blank on exospheres and magnetospheres.... there is just something thrilling about reading passages like the one above. Every world is full of complexities, often invisible to tha eye...

Hmm...decompositional products of H2O. Not far-fetched.

My guess is that the polar cometary deposit(s) are at least getting sputtered by the magnetosphere; they might even be slowly sublimating from thermal conduction via the crust. Strongly doubt that it's native Mercurian water; that had to be gone aeons ago.
QUOTE (nprev @ Jul 3 2008, 03:16 PM) *
Hmm...decompositional products of H2O. Not far-fetched.

...and we know the MS signals are not due to methane (CH4, 15 amu) or ammonia (NH3, 17 amu) because....?
Phil Stooke
... because they're at 16 and 18, not 15 and 17?

Good point, Mike. I don't think we do know with utter certainty, but the water-group ion interpretation is what they're going with as the most likely. I notice there's a nice little carbon spike, too.
I only have access to the abstract :

"MESSENGER Observations of the Composition of Mercury's Ionized Exosphere and Plasma Environment
Thomas H. Zurbuchen,* Jim M. Raines, George Gloeckler, Stamatios M. Krimigis, James A. Slavin, Patrick L. Koehn, Rosemary M. Killen, Ann L. Sprague, Ralph L. McNutt, Jr., Sean C. Solomon

The region around Mercury is filled with ions that originate from interactions of the solar wind with Mercury's space environment and through ionization of its exosphere. The MESSENGER spacecraft's observations of Mercury's ionized exosphere during its first flyby yielded Na+, O+, and K+ abundances, consistent with expectations from observations of neutral species. There are increases in ions at a mass per charge (m/q) = 32 to 35, which we interpret to be S+ and H2S+, with (S+ + H2S+)/(Na+ + Mg+) = 0.67 ± 0.06, and from water-group ions around m/q = 18, at an abundance of 0.20 ± 0.03 relative to Na+ plus Mg+. The fluxes of Na+, O+, and heavier ions are largest near the planet, but these Mercury-derived ions fill the magnetosphere. Doubly ionized ions originating from Mercury imply that electrons with energies less than 1 kiloelectron volt are substantially energized in Mercury's magnetosphere."

* Edit * : A nice summary and some answers from Dr. Zurburchen at the PS blog.
I've just been doing some back-of-envelope calculations with the new value of Mercury's magnetic dipole moment. It is given in terms of the cube of Mercury's radius (!) Converting to amp.metre squared (or equivalently tesla.metre cubed) I get 3.8 x 10 to the power 12. This compares with 14 x 10 to the power 12 for Ganymede - remarkably similar really, considering the mechanisms are likely very different. However I would welcome independent confirmation of my hasty arithmetic.

EDIT: link to abstract-;321/5885/82
Silly question re the spectrum: How come it doesn't register any hydrogen, monatomic or diatomic? Is this an instrument limitation, or is it just indistinguishable from the solar wind background?
I thought this was very interesting.

First identified shield volcano on Mercury?

Image of 95 KM wide possible shield volcano with a 25 km wide caldera, in south west Caloris Basin floor.
Click to view attachment

Map of area shown above.
Click to view attachment

My attempt at cropping & enlargening the 25 KM wide caldera.
Click to view attachment

Andrew Brown.
Nice work, Andrew! smile.gif

Sure looks like a volcano to me. I'd been expecting Messenger to find a few, although possibly not until it achieved orbit.

I'm more then a bit intrigued by the difference in color between the volcano's shield and the surrounding terrain. Will be interesting to see the age estimates of such features. Does anyone know if the rate of micrometeoritic surface erosion at Mercury is expected to be greater than that of, say, the Moon due to the fact that it's so much deeper in the Sun's gravity well?
Hi nprev,

I have given that some thought. Logic would suggest that micrometeoroid impacts to be more numerous & energetic on Mercury than on the Moon, due to the sun's greater pull @ approx 0.35 AU.

I also wonder, if it's actually very much less though, as radiation pressure & the solar wind will be greater, some 10 -11 times greater than on the Moon?

To me that feature is a volcano. The lighter material maybe ash?

I don't know if there are any higher resolution images as yet of this volcano? Would be interesting to look for lava flows, lava tubes, etc.

Andrew Brown.
Yeah...forgot about solar wind erosion, although the magnetic field presumably offers some protection from that.

Damned interesting, though. We're seeing some extremely complex features--some of those craters with mixed dark/light terrain are just mind blowing--and frankly I can only stare and say "Wow!" without attempting an explanation at this point. IIRC, one of the Messenger scientists said that Mercury is looking more like Mars then the Moon; I can believe that analogy. Certainly the crust seems to be chemically differentiated to a much higher degree then that of the Moon.
Audio of the teleconference will be streamed live at:

Howdy all -

I've been lurking for a year or two, and have been a fan of unmanned spaceflight in general for decades. First post!

I was unable to get the audio stream above to work during the news conference on Thursday. Does anyone know where I might find a recording of it, like they've been doing for the Phoenix missions?

The audio from the Phoenix pressers has been archived by JPL. APL doesn't appear, at least at first glance, to have done the same. Unfortunately we're at the mercy of individual NASA centers and their online prowess rather than a unified agency policy regarding these audio archives.

Of course, I may also not be looking in the right places. smile.gif
At the end of the briefing they listed a toll-free number to call for a replay for up to a week, but I didn't write it down -- anybody else catch it?

Just went hunting for it; no joy. You might have to contact their media coordinator on Monday, Emily. (I'll give it a shot as well because I'm working nights this week, but I ain't got your street cred! tongue.gif )

EDIT: Mike, Emily's article here goes into a lot of detail about the water-group interpretation for the 16-18 amu FIPS findings.
QUOTE (nprev @ Jul 5 2008, 09:10 AM) *
EDIT: Mike, Emily's article here goes into a lot of detail about the water-group interpretation for the 16-18 amu FIPS findings.

Thanks! I'm still scratching my head trying to understand the graph.

The mass spec data gives out an m/z (mass/charge) ratio as nicely described in Emily's post.

[I always think of mass spec experiment as a "ping and fling" You need to electronically ionize a molecular/atomic species, then accelerate it with a magnetic field, then try to wrap it around an electric field and see where it splats. A heavier chunk won't be deflected as much. Sorta like two vehicles trying to make it around too tight a bend at the same speed: A Porcshe will almost make it around the bend before it hits the guardrail, while an 18-wheeler fully loaded with a ton of bricks will plow right into the guardrail without being able to make much of a turn: looking at the two splat marks on the guardrail you can figure that that the splat with the least deviation around the curve was the heavier one.]

This particular MESSENGER instrument is looking at the already-ionized species flying around in space. (So neutral radicals won't get accelerated or detected.)

The graph shown in the post seems to have peaks at 16 and 17 and 18. So, as mentioned in the post, this could be due to charged water (H2O radical cation?, 18 amu), hydroxyl radical (-OH, 17 amu) and singly charged oxygen (O+, 16 amu) [it could also be doubly charged oxygen molecule O2++ 32/2 = 16].

That's all cool. But where I'm confused is that there appears to be a peak at roughly the same intensity at 15 amu. So this implies either a charged radical at 15, doubly charged at 30, or triply charged at 45.
(As you go up in weight there are more possibilities for combinations of elements possible to give that mass)

[As an aside, when a mass spec instrument has to ionize species itself, there is a possibility of getting transient associations flying around and giving a signal. LC-MS combinations are notorious for these effects. Many larger organic molecules after travelling through an LC-MS will generate signals composed of parent molecule + sodium [M+23], even if sodium wasn't originally present in the sample (it only takes a trace). Also when you ionize large organic molecules (like in a GC-MS, they can frag up. M-CH3 (M-15) is a common observed fragment if the parent has an ionization-labile methyl group. Most organic laboratory MS systems don't detect below 44 amu to eliminate carrier gas and atmospheric signals.]

Noway would I think that a 15 amu signal detected by MESSENGER could came from breakup of a complex organic. BUT I'm curious to know if it could be from comet-delivered ionized methane.

Looks like I'll have to download the Science paper to gets me some learnin'.

I actually wouldn't be surprised at all if there are some organic subspecies represented in that region. For one thing, it's VERY crowded in the graph, with no outstanding peaks. Secondly, if the source is indeed the cometary impact residue at the North Pole, then presumably there is an abundance of organics in the material.

There are some tantalizing concepts evident from this data; I can hardly wait until Messenger achieves orbit! One other remote possibility is that there just might be active vents on Mercury due to the continuing crustal compression...nothing big, but enough to occasionally belch out some anomalous compounds that subsequently decompose in the exosphere. We should look for spikes in abundances. smile.gif
Reminder ... Can one of you find out what that number is for the teleconference replay?
I read the Science article carefully and I think I've cleared up my misunderstanding.

From the released plot (available at:

Click to view attachment

If I understand correctly, the instrument is detecting a range of m/q (m = mass; q = charge) numbers depending on the energy of the inbound ion. The "wiggle room" for the m/q number should be a gaussian distribution. The Gaussian distributions for key m/q ratios are shown as the thinner dotted line in the graph above. It is the combination of all these Gaussian distributions that will make up the observed lines (thick heavy blue line in the figure above.

Big peaks are most likely "real", these are points that most likely correspond to a distinct species. So the peak at 16 is most likely due to O+ (16 amu). [Oxygen was detected by Mariner 10; so we know it's in there]. The peak at 18 is most likely due to water radical cation H2O+ (18 amu).

Where Gaussian curves overlap or combine, you can get a smaller peak. So the data point at m/q=17 could be due to the combination of the Gaussian centered at m/q=16 and the Gaussian centered at m/q=18. And there could also be a component of hydroxyl cation (OH+; 17 amu) which makes it's own cute little Gaussian centered at 17. [Note that this is 2 electrons away from "normal" hydroxyl anion from ionic dissociation of water -OH-->OH(+) + 2e(-); it's not a happy cation]. The combination of the 16 Gaussian + the 17 Gaussian + hydroxyl cation (OH+) + doubly charged H2S++ (m/q = 34/2 = 17) could give rise to the counts we see in the m/q = 17 bin.

The data point at m/q=19 could be due to the 'heavyside' Gaussian tail of the m/q=18 peak + a small chunk of the really big peak (and Gaussian tail) for sodium ion (Na+ at 23 amu) + some hydronium ion H3O+ (19 amu) [Not that hydronium ion is "naturally" ionized in the form of a cation.]

The data point at m/z=15 is much lower. This signal could be due to the Gaussian from m/z = 16 (O+) and other "stuff" (N+=14 amu Gaussian tail).

The upshot is that the "peaks" in the graph above are real signals and can be used to infer ionic and atomic species; datapoints outside the peaks are confounded by Gaussian tails, etc.

So to answer my own question: Is there an evident signal for methane CH4+ (m/z=16) or ammonia NH3+? (m/z=17)? Nope, there isn't.


Are there any clues in the article about the structure of the multiply charged ions at 6, 8 and maybe 10 ?
There is only limited space for ionic charges in diatomic and triatomic species, and for (assumption) doubly charged ions we are looking for MWs of 12, 16 and 20. Nice and even numbers.
I am curious.
Are the collision energetics enough to provide double ionization of atoms, like O(2+) for 8 ?
QUOTE (TheChemist @ Jul 8 2008, 11:03 AM) *
Are the collision energetics enough to provide double ionization of atoms, like O(2+) for 8 ?

From the article:
"Plasma sheet electrons are most likely to be the ionization source for the creation of multiply charged ions (such as O++) observed by FIPS from corresponding singly ionized atoms (such as O+). MESSENGER does not directly measure thermal and suprathermal electrons. However, our detection of multiply charged ions provides indirect evidence for the presence of a hot electron component near the planet and supports the indirect detection of [ca.] 1- to 10-keV electrons in the region by MESSENGER's x-ray spectrometer."

There is a pretty cool graphic in the article that shows how the measured energies and relative abundances by weight zone changed along MESSENGER's flyby track. The leading edge had the highest measured H+ ion energies (planetary motion hitting solar wind). Interestingly, this area also corresponded to the maximum of "chunks" in the m/q = 3 - 10 range. So higher electron energies also correlates to area with most multiple charged ions.

The closest approach to the Mercury had the highest weight particles (evidence that sodium and magenesium were coming from the surface and not the solar wind).

Aside from O++ specifically mentioned above(and C++ mentioned later in the article), the authors used the generic term "multiply charged ions" as a catch-all for stuff in the m/q range of 4.67-11. Outside this range, they do specify Fe++ (28), Na++ and Mg++ (11-12) and Si++ (14) as possible candidates in Table 1 of the article.

Many many thanks Mike !

(That Na++ would freak most freshman general chemistry students rolleyes.gif )
one atom to the other: "OMG, I just lost an electron!!"

other atom: "Are you sure?"

First atom: "Yes, I'm positive!"

Oh, dear Lord...a chemist channeling Henny Youngman!!! (Good one! laugh.gif )
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