The Evidence from Mercury: Inconclusive

This is an artist's conception of MESSENGER orbiting Mercury. (NASA image)

Mercury is a difficult planet to study because of its proximity to the sun. As a result, there are only two robotic spacecraft that have visited it. Starting on March 29, 1974, the Mariner 10 spacecraft flew by Mercury a total of three times, but it never entered orbit. Then, on March 18, 2011, the spacecraft known as MESSENGER (MErcury Surface, Space ENvironment, GEochemistry and Ranging) settled into a comfortable, near-polar orbit of the planet and has been studying it in detail ever since.

As a scientist, I am always excited to learn new information about God’s creation, so I have been watching MESSENGER’s progress with interest. As a young-earth creationist, however, my interest in MESSENGER was somewhat heightened, because its mission included collecting data on Mercury’s magnetic field. The young-earth model of planetary magnetic fields had made a prediction about what MESSENGER would find once it collected those data, so I was naturally very interested in the results of the measurement.

Since the previous measurement of the field was made more than 35 years ago, and since the young-earth model predicts that all planetary magnetic fields should decay fairly rapidly, the young-earth model predicted that Mercury’s magnetic field should have decayed by roughly 4 percent since Mariner 10’s previous measurement. By contrast, the old-earth model predicts no measurable change at all. Because the young-earth model has been successful in three other predictions,1 I was hoping that MESSENGER would provide a fourth.

Unfortunately, that didn’t happen.

The first paper about MESSENGER’s measurement of Mercury’s magnetic field was published way back in September of 2011, and I read it with interest. However, I decided not to blog about it right away because I wanted to make sure I really understood it. I am not a planetary scientist, and I have no expertise in studying planetary magnetic fields. As a result, even though I thought I knew what the paper meant, I wanted to make sure. So I asked a colleague of mine who has a lot more knowledge in the field to read the paper and discuss it with me. That took some time, because my colleague is a busy man.

Once our discussion was complete, I decided to take one more step. I contacted the lead author of the paper to ask him for some clarification. He graciously returned my E-MAIL promptly, so now I can confidently write about the results of MESSENGER’s measurement. They weren’t the results I was looking for, but that’s the nature of science. In science, you follow the data, no matter where they lead.

In the end, MESSENGER’s detailed measurements of Mercury’s magnetic field indicate that Mariner 10’s measurement wasn’t very good. It turns out that due to the nature of Mariner 10’s mission, it didn’t have a lot of time to make its measurement. Thus, it did a “quick and dirty” measurement, and the researchers then made some assumptions about the nature of Mercury’s magnetic field. MESSENGER has shown that those assumptions were wrong. 2

Without going into detail, the analysis of Mariner 10’s measurement required the researchers to assume a specific geometry for Mercury’s magnetic field. Reasonably enough, they assumed it was shaped a lot like earth’s magnetic field. MESSENGER has shown that this is just not true. The shape is radically different from what was assumed. As a result, it is essentially meaningless to compare Mariner 10’s measurement to MESSENGER’s measurement. Because the assumption made in the Mariner 10 analysis was so wrong, you pretty much have to throw away its measurement.

Thus, the scientific conclusion is that there is no evidence that Mercury’s magnetic field has decreased in strength since the Mariner 10 measurement. Conversely, there is no evidence that it hasn’t. The data simply cannot be compared, so there is nothing that can be said about whether or not Mercury’s magnetic field has decreased since Mariner 10. Thus, it’s not a “win,” for the young-earth theory, but it also is not a “loss.” At best, you could call it a “draw.”

Unfortunately, some young-earth creationists latched on to one sentence in the paper to try to turn this into some sort of win. The authors of the paper say this:

The best estimate for g10 is taken to be -195 +/- 10 nT (1-SD uncertainty), ~27% lower in magnitude than the centered-dipole estimate implied by the polar Mariner 10 flyby.

Brian Thomas at ICR claims that this means Mercury’s magnetic field is rapidly decaying, even faster than what the young-earth model predicts. However, it means no such thing. It means that g10, a parameter used to mathematically describe one aspect of the magnetic field, is significantly smaller than what was implied by the Mariner 10 flyby. However, since the g10 parameter depends on the assumed geometry, and since we now know that the assumed geometry was wrong in the Mariner flyby, this tells us nothing about how the magnetic field has actually changed.

In the end, then, we simply can’t tell whether or not Mercury’s magnetic field has actually changed since 1974. This is disappointing, of course, but it should not be “spun.” Science is not about spin. It is about the data, and the data tell us that we have no idea whether or not Mercury’s magnetic field has changed.

PLEASE NOTE: There is an update to this story. Dr. Humphreys published a paper trying to make the best comparison possible between Mariner’s measurement and MESSENGER’S measurement. That analysis shows support for the young-earth model.


1. It correctly predicted the magnetic fields of Neptune and Uranus before they were measured, and it correctly predicted that igneous rocks from Mars would show evidence of a former planetary magnetic field: D. Russell Humphreys, “The Creation of Planetary Magnetic Fields,” CRSQ 21,1984, (available online)
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2. Brian J. Anderson, et. al., “The Global Magnetic Field of Mercury from MESSENGER Orbital Observations,” Science 333:1859-1862, 2011.
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  1. D. Perrine March 29, 2012 8:35 pm

    Assumptions were made about the geometry of Mercury’s magnetic field in Mariner 10′s flyby. This corrupted the resulting magnetic field measurement. (As I seem to be understanding your post.)
    If the original data is still available, in raw form, no assumptions or anything, is it still viable to apply to the actual geometric configuration of Mercury’s magnetic field to access a rate of decay (or lack thereof) or was the ‘quick and dirty’ measurement have to large a margin of error to even be usable?

    • jlwile March 30, 2012 6:35 am

      D. Perrine, I expect the raw data are still available, but they might be very hard to get to. Think about it. Most likely, the data are stored on magnetic tape, as that was considered the “permanent” data storage medium back then. Is there a computer around that can read a magnetic tape that was written in 1974? The question is whether or not anyone is interested enough in this question to try to find the raw data and figure out what it means now that we know the geometry.

  2. WSH March 29, 2012 10:44 pm

    Well, the track record of standard magnetic dynamo theory hasn’t been particularly successful at planetary field predictions. I would love to get a more conclusive perspective on Mercury’s field strength ten years or so down the road, though. Thanks for the update, as I have been waiting to hear about the results of Dr. Humphrey’s theory applied to Mercury for some time.

    • jlwile March 30, 2012 6:37 am

      WSH, you are right about the dynamo theory. Humphreys’s theory has enjoyed a lot more success when it comes to the data. I think it would predict a measurable decay in as little as 15 years, so if nothing else, we just have to wait a while.

  3. D. Perrine March 31, 2012 9:38 am

    I did not realize that this was how it was stored. Maybe it is because I like pens and paper better than computers but I thought everything would be archived on paper. But, I guess that doesn’t make much sense if the scientists do all their work on computers, analyzing data.

    • jlwile March 31, 2012 12:12 pm

      Remember, D. Perrine, that the data were sent electronically from Mariner 10. Thus, it makes most sense that it would be stored electronically.

  4. Mia April 2, 2012 3:27 pm

    It’s nice that a 28-year old paper can still claim to be unfalsified. That’s some stolid, I mean solid, research.

    How do YECs dispute the data about light traveling billions of light years by the time it reaches us? This article prompted the question:

    “The maps analyzed so far are based on data from the first year and a half of observations, and contain more than 250,000 galaxies, some more than six billion light years away.”

    Is it a measurement problem or we haven’t got the speed of light quite right?

    • jlwile April 3, 2012 6:19 am

      Mia, it’s not just that the model hasn’t been falsified. It has three successful predictions under its belt. That’s the really important part.

      You ask an excellent question. I expect the distance measurements are mostly correct, and while there are even some secular cosmologists who would like the speed of light to have varied in the past, I am skeptical of such views. The important thing to realize is that there are some underlying assumptions you must make in order to believe that light from billions of light years away took billions of earth years to get here. You are assuming that the mass of the universe is spread out fairly evenly across the universe, that the universe is expanding with no particular geometry, and that the earth isn’t in any special place in the universe. If one or more of those assumptions are wrong, general relativity tells us you can’t determine the time it takes light to travel across the universe and arrive at earth.

      General relativity tells us that time passes differently depending on the local gravitational fields. It passes quickly when the gravitational fields are low and slowly when the gravitational fields are high. This might sound odd, but it is really true. For example, time passes more quickly for the GPS satellites than it does for us on the surface of the earth, because they experience a lower gravitational field from earth’s gravity. (There is actually a second effect that works in the opposite direction due to the satellites’ speed, but that effect is small compared to the effect of the gravitational field.) If we didn’t take into account that time passes more quickly on those satellites, the GPS would not work.

      Well, if we assume that the universe’s expansion is spherical (which is not what the Big Bang assumes) and that earth is somewhere near the center of this expansion, an interesting thing happens. During the expansion of the universe, time passes more quickly the farther away you are from earth. As a result, while only a few thousand years may have passed on earth, many billions of years may have passed on the edges of the universe. If this is the case, then there is no problem with light from billions of light years away reaching earth in thousands of earth years, because time passed slowly on earth compared to the outer reaches of the universe. Here is a more detailed discussion of this idea.

  5. Ben Fournier April 6, 2012 12:45 am

    Is the geometry of Mercury’s magnetic field due primarily to its radius from the sun or is there yet more due to internal composition? I would suppose that the primary source of asymmetry would be due to its radius from the sun and secondarily due to internal composition, but what’s the actual case so far known?

    • jlwile April 6, 2012 8:43 am

      Ben, the Science article didn’t address why the geometry is so odd. I expect that you are right, however. With Mercury’s proximity to the sun, it experiences very strong tidal forces that deform the planet to some extent. I expect this affects the magnetic field dramatically.

  6. A homeschooled science geek April 20, 2012 1:36 pm

    Dr. Wile,

    I recently found your blog. Awesome work!

    I had a discussion with a professor about the geometry of the universe. He thinks that the EXTREMELY small dipole of the cosmic background radiation indicates that earth is near the center of the universe.

    That also can mean that the expansion is pretty much uniform as well.

    He thinks the balloon example of the universe does not show that the universe has no center. I agree because as far as we know the universe doesn’t come back on itself.

    I can testify due to his conversation with him that the assumptions in your comment are at least reasonable.

    Keep up the good work!

    • jlwile April 21, 2012 7:17 am

      Thanks, science geek. I am glad that you have been speaking to a knowledgeable professor on these matters. I hope you continue to enjoy the blog!