The Planets: “Mercury, the Winged Messenger,” Part 4 (of 10)

Maureen's Musings - Tuesday, August 5th, 2008

With the 2008 Olympics in Beijing just days away, it is appropriate that the next planet in this series derives its name from a mythological deity known for his own athleticism and patronage of mortal sportsmen. Mercury, messenger to the Roman gods, is easily recognizable, as is Hermes, the Greek deity from which Mercury was pilfered. Both versions feature winged-shoes and/or -cap and a caduceus, among other symbols. The Mercury movement from composer Gustav Holst’s suite The Planets reflects the character’s quick flight and activeness.

The planet Mercury is now officially the smallest planet in our solar system, and is also the closest planet to the sun. It shares some attributes with Earth’s moon, including its size and heavily cratered surface, but unlike Earth itself, it has no natural satellites and no substantial atmosphere.

Yet Earth and its distant neighbor do share some qualities in common. For example, Mercury has a magnetic field, albeit a very weak one compared to Earth’s. Mariner 10 made this discovery during its Mercury flybys in 1974 and 1975. The presence of a magnetic field challenged scientists’ previously held notions that Mercury, due to its size, had an iron core, as opposed to a molten one like Earth’s. Further research in 2002, using massive antennas to send radar signals to Mercury, showed that the planet wobbles slightly as it orbits the sun—which reinforces the evidence for a molten core. (See here and here for further discussion of these discoveries.)

Thanks to NASA’s own winged MESSENGER, launched four years ago, scientists have continued to unravel Mercury’s mysteries. Several articles from Science Daily report on some of MESSENGER’s discoveries during its first flyby of the planet January 2008 (see here, here, and here.) But why should we bother to study Mercury? What can this inconspicuous little orb tell us?

In a Science Daily article describing the discovery of Mercury’s wobbly orbit, Professor Jean-Luc Margot of Cornell University, Ithaca, N.Y., explains that,

“The chemical composition of Mercury’s core can provide important clues about the processes involved in planet formation,”… “It is fundamental to our understanding of how habitable worlds—planets like our own—form and evolve.”

RTB’s Jeff Zweerink has pointed out that the shared characteristics between Earth and other planets, like Mercury, still help to highlight Earth’s uniqueness:

Further, planets containing water may be far more common than previously thought (water is the universe’s second most abundant molecule), as are planets that briefly exhibit geological activity such as plate tectonics and volcanism. However, the combination and durability of Earth’s water cycle, plate tectonics, and magnetic field generation 4.5 billion years after its formation strongly argues for supernatural intervention. (emphasis original)

Like Mars and Venus, Mercury serves to reinforce the exceptionality of Earth. Yet their similarities also help us gain a better understanding of the world we live in and its history, and, hopefully, expand our appreciation for the Creator who so lovingly engineered the planets.