June 18, 2011 | David F. Coppedge

Mercury Orbital Science Begins

Now that the MESSENGER spacecraft has settled into its orbit, systematic detailed observations are coming in.  The Carnegie Institution has posted preliminary findings from the orbital science tour, rejoicing that “Tens of thousands of images reveal major features on the planet in high resolution for the first time,” and confessing that the data are confirming some predictions and revealing surprises.  Among the surprises, “Mercury’s surface composition differs from that expected for the innermost of the terrestrial planets, and Mercury’s magnetic field has a north-south asymmetry that affects interaction of the planet’s surface with charged particles from the solar wind.” 

Embedded in the review are links to instrument descriptions at the MESSENGER website, where photos and presentations from a press conference have been posted. The mission is managed by the Applied Physics Lab at Johns Hopkins University.

Update 06/20/2011: Live Science posted a list of “The Greatest Mysteries of Mercury.”  It concerns the planet’s density, magnetic field, and atmosphere.


This is a historic year for exploration of Mercury.  The three prior flybys already tantalized planetary scientists, but now floods of images and data can be expected for three years.  It’s been a long time since Mariner 10 visited in 1971 with a few brief passes.  Readers should applaud the designers and operators of this successful spacecraft.

Note the difference between the discovery and explanation phases of science.  Discovery does not always follow a method.  Discoveries can come by mistake, by accident, by a dream, a hunch, tacit knowledge, abductive reasoning, or planning new ways to get closer to a target of investigation.  The latter might include a ladder, climbing a higher peak, venturing farther into inhospitable environments, or sending better robotic observers where human senses cannot go, as in planetary exploration.

Explaining the observations is a different matter entirely.  Observations may suggest explanations, may falsify or confirm predictions, but do not explain themselves in a vacuum.  Remember to keep discovery and explanation distinct when reading articles such as these.  Scientists and their reporters often mix them together, giving the impression there is only one explanation.  That may be the case, but must be demonstrated, not assumed. Often the surprises and anomalies are the most interesting parts of the story.

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