Posted by jlwile on March 29, 2012Mercury 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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