Snowballs from Space
Published: January 17, 2004
By JOHN DAY
For the News-Register
Our home, Planet Earth, is a very wet place. In contrast, our neighbor, Mars, is a desert.
Three-quarters of Earth's surface is covered by water. It's mainly in liquid form, though ice exists over the northern and southern polar oceans and water vapor is present in the atmosphere.
Being 93 million miles from the sun, conditions are such that water "sticks" to our planet. All three phases can coexist, so water remains a prominent feature.
Dating of meteorites indicate that our solar system is about 4.6 billions years old. The older sedimentary rocks, formed through processes requiring water, are about 3.9 million years old.
Water must have been present at least that long ago then. It is not clear where this water came from, but the traditional view has been that it was a byproduct of planetary cooling, our seas resulting from the condensation of water vapor originating in the rocks of the Earth's crust.
In the last decade, some new and radically different ideas have emerged from the scientific community, particularly from University of Iowa astrophysicist Louis A. Frank.
Frank took note of mysterious dark spots in high-resolution photographs taken in the high-elevation mesosphere of the polar regions. He hypothesized that they might be house-sized, 40- to 60-ton ice balls from small comets that were entering the atmosphere at the astonishing rate of 40,000 a day.
This far-out hypothesis was not widely embraced by geophysicists. It sounded ridiculous.
But confirming evidence has come from an orbiting instrument launched by the Naval Research Laboratory. It features a high-resolution spectrograph that has detected abundant hydroxol radicals in the high atmosphere - 50 to 80 kilometers up.
These are the byproducts of water. And calculations shown to the American Geophysical Union provide strong evidence that such an extraterrestrial source could account for the entire mass of water contained in our oceans.
Fairly recently, it has been discovered that Europa, one of Jupiter's moons, seems to have an ocean of liquid water beneath a crust of ice. A fuller explanation presents a challenging scientific mystery.
One of water's unique properties is that it is nature's best solvent.
Chemists tell us that the long molecular chains and branching structures of carbon make it the ideal chemical backbone of life. And water is the ideal solvent in which carbon-based chemistry can begin.
Where did this water come from in the first place?
The writer acknowledges a variety of articles found on the Internet for providing the basis for this essay. And they point to a possible answer to that question.
A team of U.S. astronomers has discovered a large concentration of water vapor in a cloud of interstellar gas close to the Orion Nebula. The Orion Molecular Cloud, composed primarily of hydrogen molecules, lies in a particularly good location for new star formation, and water vapor is a byproduct.
Looking in the far-infrared region of the spectrum, astronomers have observed water vapor's characteristic signature.
Could our H2O be stellar stuff itself? An intriguing thought!
John Day is a retired Linfield College physics professor and an avid meteorologist.
