Headline News Internal Communications Branch (P-2) NASA Headquarters Friday, February 22, 1991 Audio Service: 202 / 755-1788 This is NASA Headline News for Friday, February 22, 1991 Kennedy Space Center launch team staff are proceeding with preparations for Shuttle Mission STS-39. Analysis of hinge cracks on Discovery's fuel line door mechanisms continues. The launch team began hypergolic fuel loading into the orbital maneuvering system tanks last night. No decision on whether to fly "as is" or bring Discovery off the launch pad for repairs has been made yet. As part of this ongoing analysis, a door closure test is scheduled for late this weekend on Columbia's fuel door mechanisms. This test and analysis of the results are expected to be complete in time for management's assessment at the STS-39 Flight Readiness Review. Atlantis and Columbia have been examined to determine if similar conditions exist on their door mechanisms. No cracks have been found in the ET door mechanism on Atlantis, now scheduled to launch in April on its Gamma Ray Observatory deployment mission. Inspection of the door mechanism on Columbia has revealed three small cracks. Analysis of Columbia's situation continues. * * * * * * * * * * * * * * * * Scientists, using new data provided by the Magellan spacecraft, are currently testing four competing theories concerning the nature of the continent-sized highland region on Venus known as Aphrodite Terra. Aphrodite Terra, the largest of the Venus' highland regions, extends nearly two-thirds of the way around the planet. Magellan has completed radar mapping of this region. Earlier data provided by Pioneer Venus Radar Mapper suggested that Aphrodite Terra's regional topography might be similar to Earth's continents. The four current hypotheses state that the highland region is: 1) An ancient continent, formed from lighter rock that crystallized early and literally floated on Venus' dense mantle; 2) A spreading ridge analogous to the mid- ocean ridges on Earth where new crust is being formed as the continents drift apart; 3) A hot spot similar to the hot spots beneath the island of Hawaii where the mantle is rising, producing broad domes; and 4) A region of mantle downwelling where a plume of colder, more dense mantle material causes the surface crust to compress and thicken allowing the thicker region to stand higher. Advocates of all four hypotheses are members of the Magellan science team and have created a continuous "lively debate" according to project scientist Steve Saunders. * * * * * * * * * * * * * * * * As a continuation of NASA's support for National Engineers Week, Adm. Truly will teach a ninth grade geometry class at George Washington Junior High School in Alexandria this afternoon. Adm. Truly will tell students how math and science relate to the exploration of space and show the students how engineering can turn ideas into reality. Here's the broadcast schedule for Public Affairs events on NASA Select TV. All times are Eastern. NASA Select TV is carried on GE Satcom F2R, transponder 13, C-Band, 72 degrees W Long., Audio 6.8, Frequency 3960 MHz.**indicates a live program. Monday 2/25/91 9:00 am STS-37 flight director mission briefing, live from Johnson Space Center. 10:00 am Gamma Ray Observatory science and spacecraft briefing, live from Goddard Space Flight Center. 2:00 pm STS-37 flight crew briefing, live from JSC. All events and times may change without notice. This report is filed daily, Monday through Friday, at 12:00 pm, EST, It is a service of NASA Headquarters Office of Public Affairs. Contact: CREDMOND on NASAmail or at 202/453-8425.