The Mercury ice excites everyone who hears about it. After all, people forget that even Mercury has areas of endless shadow cold enough to hold ice. But they smugly assume that the ice would sublimate slowly, if at all, even over billions of years. If the ice rested quietly, and nothing disturbed it, then it would stay, even that long. But it does not rest quietly. Meteors of all sizes bombard it all the time. In millions of years, and certainly billions, those meteors would have blown the ice away.
The Mercury ice problem
The MESSENGER rocket probe now confirms that Mercury has ice on both poles. The south mercurial pole alone has enough ice to bury Washington, DC 2.5 miles deep. Most scientists agree that comets, and perhaps some water-laden asteroids, carried the Mercury ice to Mercury. As these (and other) objects fell, they made craters that would stay in shadow forever. Mercury has no atmosphere, so the water vapor would condense, freeze, and collect in those craters.
But why does Mercury still have so much ice on its poles? Would the ice stay there? How fast does water ice sublimate away from a deep-cold (100 kelvin) region?
Conditions of the Mercury ice
The conditions that affect the Mercury ice are more than the surface temperature of the craters that hold it. At 100 kelvins, any of those giant cups should hold that ice for a long time. Especially if the ice is dirty.
If, that is, nothing disturbs the ice.
But something does disturb the Mercury ice. The planet Mercury has meteors falling on it all the time. This makes Mercury no different from Earth’s Moon, or Ganymede, or Pluto, or any other dwarf planet or satellite that has no atmosphere. Those meteors can be as lightweight as one ten-trillionth gram (or lighter), and as heavy as 2.71 quintillion grams. And the lighter-weight the objects, the more of them bombard any airless object every second.
Uniformitarianism demands that any process we measure today, has always lasted, and at the same rate, and certainly no slower. Furthermore, conventional astronomers say that a vast number of meteors bombarded the Moon, and by inference Mercury and all other airless objects, from 4.1 to 3.8 billion years ago. This second fact applies to the Mercury ice if we assume the Oort Cloud theory of comets. For any other theory, only the “background bombardment” would apply.
So even under usual conditions, a constant stream of boulders, rocks, and dust—lots of dust—falls on Mercury all the time. This dust has no atmosphere to slow it down. So it hits just as fast as it came in. It vaporizes at once and turns anything it hits into powder—or vapor. (In fact, the dust on the moon is 66 parts pulverized Moon rock and one part meteoritic dust.)
After millions of years of that, no amount of water ice would last. Certainly not enough to bury a major US city two and a half miles deep! And if the Mercury ice got to Mercury ahead of the Late Heavy Bombardment, that episode alone would have blown the ice to the solar winds. And remember: Jan Oort suggested the comets all formed 4.5 billion years ago in the Great Solar Nebula.
What happened instead?
Instead, the Mercury ice fell to Mercury, not billions or even millions of years ago, but thousands. Forty-four hundred years ago, give or take ten, to be more precise. (The date that Nebuchadnezzar II destroyed the first Jewish Temple, the king lists of the Kingdoms of Israel and Judah, and the annals of Moses, Joseph, Jacob, Isaac, and Terah, let us fix the date: 2349 BC.) The Early and Late Heavy Bombardments were both one. Those heavy objects fell first, and then the comets holding all the water that became the Mercury ice. And from that day to this, meteors, from microscopic to boulder-sized, have chipped away at the Mercury ice. But four and a half thousand years is not long enough for those objects to blow that ice out of those craters.
Thus the Mercury ice is a memorial to the greatest catastrophe the Earth ever knew. That catastrophe also affected many other objects in the Solar system, including Mercury.
Thanks to Walter T. Brown, Jr. for sharing his insight into the problem of the Mercury ice and how meteoric bombardment should have affected it much more than it has.
Reprinted from Conservative News and Views