NASA has announced plans to study Hale-Bopp using spacecraft, sounding rockets, and telescopes, as the giant comet approaches the Sun and brightens in the night sky.
     A series of four sounding rocket launches, scheduled between March 24 and April 5, will allow observations of the comet at ultraviolet wavelengths. The launches, using two-stage Black Brant IX rockets, will take place at the White Sands Missile Range in New Mexico.
     NASA will also use the Ulysses spacecraft, originally launched to study the Sun, to study the effects of the solar wind on the comet. The NASA/ESA spacecraft will examine what happens to the comet, particularly its plasma tail, as it passes through different solar wind conditions at different latitudes.
     The Polar spacecraft, launched to study the magnetosphere, will also provide images of the comet in ultraviolet and visible wavelengths. Astronomers have already been using NASA's Infrared Telescope Facility (IRTF), a 3-meter (120-inch) telescope on Mauna Kea, Hawaii, to study the comet at infrared wavelengths.
     One major spacecraft that will not be taking part in the study of Hale-Bopp will be the Hubble Space Telescope. The comet is currently too close to the Sun to allow the HST to safely observe the comet. The comet will not be far enough away to permit HST observations until this fall. Hubble took images of the comet from 1995 through October 1996.
     The comet, which is up to 40 km (25 mi.) in diameter, is one of the largest comets ever seen. Although it will not pass close to the Earth, the comet is still a bright naked-eye object with a magnitude near zero. It is easily visible in the northern hemisphere in the eastern sky before sunrise and in the western sky just after sunset. The comet will become easier to see in the evening sky over the next several weeks.

[Editor's Note: For more information about Comet Hale-Bopp, including the most extensive list of Web sites devoted to the comet, visit http://www.seds.org/spaceviews/halebopp/ ]

A committee of the National Research Council recommended the NASA enact safeguards to prevent any contamination from microbes in soil samples returned from future missions to Mars.
     While the committee acknowledged that the risk of contamination is very small, it suggested the space agency set up a special lab to study the samples to prevent contamination of and by any microbes contained in Martian rocks.
     "The risk is near zero, but near zero is not zero," said panel member Norman Pace, a biologist at the University of California at Berkeley.
     Currently, the only Martian samples are meteorites blasted off the Martian surface which make their way to Earth. An examination of one of those meteorites, ALH84001, showed evidence of possible primitive life on Mars, billions of years ago.
     NASA is planning a sample return mission to Mars by the year 2005. The committee's recommendations were directed towards handling samples returned to Earth from such a mission.
     The panel doubted that any Martian life could survive the trip to Earth, or conditions on Earth itself. However, the committee felt that the safeguards it recommended would be easy for the space agency to set up and far less costly than the quarantine measures used for the first groups of astronauts who returned from the Moon.

Scientists studying global temperature data collected from a series of satellite have disputed claims that the data shows a slight cooling of the Earth in recent years, instead claiming that the data show a slight warming of the planet.
     In an article in the current issue of the journal Nature, scientists James Hurrell and Kevin Trenberth of the National Center for Atmospheric Research reanalyzed data collected by microwave sounder units (MSUs) on board a series of polar-orbiting weather satellites.
     The data from the MSUs has showed a small temperature decrease of 0.03 to 0.05 degrees C per decade, in contradiction to temperature readings on the surface, which show an increase of 0.1 degrees C per decade. Hurrell and Trenberth believe that transitions between MSUs on different spacecraft may be creating spurious temperature drops which mask a real increase in global temperature.
     Their findings were criticized by scientists at the University of Alabama and the NASA Marshall Space Flight Center, who have been analyzing the data from the MSUs since 1979. "There isn't a problem with the measurements that we can find," said Dr. Roy W. Spencer of Marshall.
     "Over Northern Hemisphere land areas, where the best surface thermometer data exist, the satellites and thermometers agree almost perfectly," said Dr. John Christy of the University of Alabama Huntsville. Spencer said he believed that the methodology Hurrell and Trenberth used in their models was likely flawed.