In Brief; July 1999; Scientific American Magazine; by Staff Editors; 2 Page(s)

Mars Bars-Magnetic patterns in its now cold crust indicate that Mars once had enough heat to spin its iron core and generate a magnetic field, says the Mars Global Surveyor magnetometer team in the April 30 Science. The patterns also hint that Mars may have had processes similar to plate tectonics on Earth. Flip-flops in Earth's magnetic field imprint material along spreading ridges, where rising magma pools on either side and then cools. The magnetic reversals and spreading, caused by the motion of crustal plates, create a unique pattern on either side of the ridge. Such symmetry has yet to be seen on Mars, however, so its past tectonics may have been different.-Christina Reed

Multilegged Mayhem-At least one culprit has been identified behind some of the deformities seen recently in frogs in the U.S. Stanley K. Sessions and his colleagues at Hartwick College report in the April 30 Science that growth of extra legs can result directly from a trematode, rather than from the other suspects, pesticides that may mimic deformity-inducing retinoids. The minute trematodes, called Ribeiroia, burrow into the hind limb buds of tadpoles, wreaking havoc with leg growth. The crippled frogs may help their parasitic cargo infect its primary host-when the frogs fail to escape a hungry bird.-Jessa Netting