Catherine McDonald, age 11, of Nashwaaksis, N. B., Canada, for her question:

What would be left if Jupiter's ice melted?

Some astronomers suspect that giant Jupiter has a metallic core about 37,000 miles in diameter. The rest of our biggest planet is thought to be built up from shell upon shell of frozen ices. These icy layers are various frozen gases and Jupiter would have to come a lot closer to the sun to melt them. But if this impossible event occurred, the biggest planet of the Solar System would dwindle away to a fraction of its present size. The dense, solid core would be only about five times thicker through the middle than Venus or Earth, and it would be only about half the diameter of Saturn, which is also believed to have a huge shell of frozen gases.

Nobody, of course, has dug down to analyze the inner structure of Jupiter. The  suggested picture is based on known facts about its size and density, the substances  in its atmosphere, its distance from the sun and what its frigid temperature must do  to its materials. Jupiter is more than 1,300 times bigger than the earth but only  317 times heavier. Its thick onion skins of ice and slush are lightweight materials.  Most of its weight must be buried in its solid center. This is estimated to be six  times heavier than an equal amount of water.