Science for Thought

Mercury Mysteries

Mercury Mysteries

This is yet another thing that science is confused about. Mercury is an enigma because it doesn't make sense.

For one thing, it's the closest planet to orbit the Sun, and because it's so close to the Sun, it's difficult to study. Telescopes turned on the Sun would be damaged and when it's in opposition, it's small and hard to observe.

Mercury has water! How in the heck is that possible? One side of Mercury is roasted by the Sun and is at 800 degrees F. The other side is very cold at -300 degrees F.

The answer is that water on Mercury is in the form of ice that lies in craters in the North Polar region that are shaded. This is how our moon contains water in its South Polar Region. Mercury does rotate 3 times for every 2 times around the Sun, but its axis isn't tilted so that craters in the North Polar Region of Mercury are shaded. It's thought that the ice came from comet collisions, just like the water on the Moon. The water frozen in craters will never evaporate despite the fact that Mercury has no atmosphere.

Another mystery about Mercury is the fact that it's too small. It contains a large iron core relative to its size, but its mantle is thin. This suggests that glancing collisions from Moon-sized planets stripped off Mercury's surface crust. In other words, Mercury started out large, perhaps as much as 4 times the size of Mars, but got smacked around, causing it to lose two thirds of its material. One theory says that the lost pieces of Mercury are orbiting the Sun very close, which is the reason they're called Vulcanoids. If they do exist, they are too close to observer or detect.

Another possible theory is that Earth stole Mercury's mantle. The evidence for this is that Mercury contains volatiles like Potassium. These should have been vaporized away long before now because of head-on collisions. The theory is that Earth and Venus captured most of the inner solar system's material. Mercury could have smacked into Earth with a glancing blow and this would have preserved the volatiles. Mercury would have been trimmed down in size because of these collisions and it means that Mercury's missing mantle is probably in Earth.

Yet another mystery is why Mercury is so dark. Most planets are much lighter in hue despite the formation of basalt from volcanic activity. The answer is that Mercury has graphite, a form of carbon on top of its basalt. This graphite came from comet collisions, not from volcanic activity. Mercury has plenty of craters to prove that it has been hit often, and the comet collisions on Mercury are much more energetic because comets nearer the Sun move much faster than they do out further. However, one theory says that Mercury's surface with carbon was that way at its formation and moved to the surface because graphite is much lighter than heavier material. The evidence for this is that impact craters reveal the carbon contained in Mercury's crust as seen by the Messenger probe.

Mercury is still active geologically. The evidence for this is the existence of large cliffs two miles high called fault scarfs. These are evidence of tectonic activity on Earth, which are caused by movement of tectonic plates. Mercury has only one large plate and its fault scarfs are caused by Mercury's crust shrinking since its formation. Evidence also exists for the fact that Mercury is still shrinking because Messenger has imaged small fault scarfs.

The real mystery of Mercury is that over time Jupiter's gravitational pull could yank Mercury out into a wider swing that could impact Earth. Ouch! The odds of this happening are small and wouldn't happen for a billion years.

Thanks for reading.