Despite the recent communications problems with the Mars Pathfinder lander, data returned previously by the spacecraft has provided scientists with new information about the surface and interior of the planet.
     Images from the Pathfinder lander, also known as the Sagan Memorial Station, and the Sojourner rover have provided additional evidence that liquid water once flowed on the Martian surface. The images, which show evidence of sand, instead of pebbles or dust, also point to the wind as a force that helped shape the Martian surface through erosion.
     "We've made significant progress in establishing that water was a dominant agent in forming the surface, and now we can say that there is another agent at work, and that is the wind," said Dr. Wes Ward of the U.S. Geological Survey's Flagstaff office.
     The discovery of sand, intermediate in size between pebbles and dust, likely requires the existence of water to create it, geologists said. The sand seen in the Pathfinder images has been shaped into small dunes by the wind.
     "What the data are telling us is that the planet appears to have water-worn rock conglomerates, sand, and surface features that were created by liquid water," said project scientist Dr. Matthew Golombek. He added that if later data showed rocks to be made of composite materials -- rocks of different types brought together by sedimentation -- it would mean liquid water once flowed there, a "very important finding."
     Scientists measuring the Doppler shift of the radio signals from Pathfinder has also found evidence of a separate core for Mars. "By measuring the spin axis of Mars, we can learn something about the interior of the planet, because the speed of the change of its orientation is related to how the mass is distributed inside," explained Dr. William Folkner.
     Data from Pathfinder show that Mars may have a solid iron core at least 1,300 km (800 mi.) in radius, or a combination iron-and-sulfur core about 2,000 km (1,200 mi.) in radius. The radius of Mars itself is 3,400 km (2,100 mi.).
     The existence of a core implies the planet was geologically active for some time early in its history, which could have in turn helped create conditions on the surface more hospitable for life by recycling carbon dioxide and other gases.

Scientists studying data returned from the Galileo spacecraft have discovered on two Jovian moons evidence of organic molecules, one of the key building blocks for life.
     Writing in the journal Science October 10, a team led by University of Hawaii geophysicist Thomas McCord found evidence of organic molecules on the two outermost Galilean satellites of Jupiter, Ganymede and Callisto.
     The discovery raises the possibility for a similar discovery on Europa, a moon which already has a heat source and may have liquid water below its surface, two essential ingredients for life. "That the organic molecules might also be on Europa is a tantalizing possibility," McCord said.
     McCord told UPI an analysis of similar data from Europa is ongoing, and expect to have preliminary results completed by December.
     The organic compounds found on Ganymede and Callisto were in much higher concentrations that expected. The source of the organics is believed to be material from comets and interstellar dust.

Astronomers using an infrared camera on the Hubble Space Telescope have found evidence for what may be the most luminous star yet discovered, a giant star ten million times brighter than the Sun hidden within a nebula.
     The Pistol Star, named for the pistol-shaped nebula surrounding it, unleashes as much energy in six seconds as our Sun does in one year. If placed in the solar system, it would fill the inner solar system out to the orbit of the Earth.
     The star, hidden behind dust clouds in the plane of the Milky Way, was first noticed in the early 1990s but not fully studied until recently. It is believed the nebula that surrounds it was formed in the early stages of the star's life 1-3 million years ago when it shed much of its early mass.
     At an initial mass of 200 times the Sun's, the Pistol Star "may have been more massive than any other star, and now it is without question still among the most massive," said UCLA astronomer Don Figer. "Its formation and life stages will provide important tests for new theories about star birth and evolution."
     Although formed just a few million years ago, the star's life is expected to be rather short. Fusing its hydrogen fuel at a tremendous rate, it is expected to end its life in a brilliant supernova in just 1 to 3 million years from now.