PASADENA— The Galileo probe that dropped into Jupiter's atmosphere last December detected a surprisingly small amount of water. But scientists at the California Institute of Technology have new thundercloud photographs and a theory to suggest that the solar system's largest planet may be "wet" after all.

PASADENA— Biologists have identified a gene that determines whether a given cell in a human or animal embryo will become a neuron rather than some other kind of cell.

Submitted by: Audra Martin, La Puente

Answered by: Bill Bottke, Postdoctoral Fellow, Division of Geological and Planetary Sciences

The short answer is that we do not know where the moon came from. It's difficult to know, because we have too few examples. Earth is the only terrestrial planet (that is, the only planet within the inner solar system, and made of rock as opposed to gas) that has a large satellite.How do we know that meteorites come from Mars?

Scientists have developed a simple diagnostic test for transmissible spongiform encephalopathies (TSEs), a group of invariably fatal brain diseases that include "Mad Cow" disease in cattle and Creutzfeldt-Jakob disease (CJD) and kuru in humans. New Diagnostic Test Announced for Group of Brain Diseases September 1996 96

Neuroscientists have new results on how our brains and eyes work together in getting our bodies from point A to point B without mishap. The research appears in today's issue of the journal Science. New Research Shows How the Eyes Help the Body Navigate September 1996 96

Question of the Month Question from: Matthew, age 8 1/2, Pasadena

Answered by: Doug Michael, PhD, Senior Research Fellow in Physics

Magnets stick together because they have a magnetic field around them, and this field both pulls on and pushes away other magnets.

If you've played with magnets like those that stick to your refrigerator, you know that sometimes they stick to each other, but that they also can push each other away, depending on which way the magnets are pointing.

Question of the Month Answered by: Lee Silver, W. M. Keck Foundation Professor for Resource Geology

The San Gabriel Valley contains huge amounts of gravel because the San Gabriel River carries broken rock out of the nearby San Gabriel Mountains. The San Gabriels produce especially large amounts of gravel for several reasons.

Question of the Month Answered by: Russ Jacobs, Ph.D., Member of the Beckman Institute, Biology

Magnetic resonance imaging machines, or MRIs, use strong magnetic fields and radio waves to look inside a patient without the need for surgery or the use of damaging radiation such as X-rays. MRIs have become standard equipment in many hospitals over the last decade.

PASADENA—The 10-meter Keck II Telescope will be dedicated in a mountaintop ceremony at 11:00 a.m. (Hawaiian Time) on Wednesday, May 8. Keck II and its five-year-old twin Keck I are the world's largest optical telescopes.

Edward C. Stone, director of NASA's Jet Propulsion Laboratory and chair of the board of directors of the California Association for Research in Astronomy (CARA), which owns and operates the telescopes, will lead the ceremony inside the Keck II dome on the summit of Mauna Kea, a 13,796-foot dormant volcano on the Big Island of Hawaii.

Question of the Month Answered by: Michael Harrington, Member of the Beckman Institute at Caltech in biology

Formally called bovine spongiform encephalopathy—or BSE for short—mad cow disease is the common name of a fatal illness that many cattle in the United Kingdom have. Bovine means related to cattle; encephalopathy has Greek roots and means brain disease; and spongiform means literally "in the form of a sponge." Put it all together, and BSE is a disease of cattle in which the brain ends up looking like a sponge, full of holes.