Marlo Vuyk, age 12, of St. Catharines, Ontario, Canada, for her question:

Does the sun have craters like the moon?

Both the sun and the moon have wretched complexions. Their entire faces are mottled with spots and rashes, blotches and blemishes. But there is a big difference. On the moon the pitted craters, wrinkles and ridges are permanent scars, older than the geographical features of the earth. The spots and blemishes on the radiant face of the sun chance from moment to moment.

Our astronauts landed, studied and photographed the surface of the moon, brought back samples of lunar rocks and lunar dust. But scientists still cannot explain exactly how the lunar craters were formed. No doubt many of them were gouged out by falling meteorites. But perhaps others were caused by ancient volcanic activity. However, we do know that the blemishes are permanent scars in the timeless face of the solid moon.

The sun's blotchy complexion is a very different story. Our dazzling star is made entirely of gases, seething in constant turmoil. Its blemishes soon subside  while new ones erupt. What's more, its dazzling disk is 400 times wider than the

face of the moon, so everything is on a grander scale. The lunar craters range from a dent you can punch with a stick to the size of a smallish province. There is no weather to erode them and some have remained more or less unchanged for maybe billions of years. A large sunspot is big enough to engulf thousands of earth sized planets. But after a couple of weeks or so it subsides and disappears.

The sun's dazzling disk is too brilliant for human eyes. Even astronomers must observe it indirectly. They study the shadows it casts on a screen, use special telescopes and photograph it in ultraviolet or other light to reveal non visible features. The view from the earth, of course, must pierce through the sun's enormous gaseous atmosphere, down through the colorful chromosphere layer to the surface below.

The surface is the photosphere, the light giving layer, and we cannot see through it to the denser gases below. Photographed in certain lights, its round face looks like a boiling sea of dazzling eruptions accented with slightly dimmer shadings. Brilliant bubbles erupt and subside every few minutes. It is hard to realize that these so called granules may be 1,000 miles wide. And everywhere the seething gaseous surface heaves and tosses in tumultuous waves.

These features always cover the sun's entire face. But from time to time there are special eruptions. Stormy sunspots form enormous dark blotches. Solar flares blaze up like cosmic candles. Vast fountains of firey gases spurt thousands of miles into the solar atmosphere like fantastic fireworks. But all the sun's features change from moment to moment and none of them last very long. Meantime the solid moon rotates and revolves, turning its permanent scars on this side and that side to face the boiling gases of the sun.