Paula Cleggett-Haleim Headquarters, Washington, D.C. March 13, 1992 (Phone: 202/453-1547) Kari Fluegel Johnson Space Center, Houston (Phone: 713/483-5111) RELEASE: 92-35
Were the channels seen on the surface of Mars carved by once great torrents of rushing water or by some other process?
Dr. Everett Gibson of NASA's Johnson Space Center (JSC), Houston, Planetary Sciences Branch; Dr. Haraldur Karlsson, formerly a National Research Council postdoctoral fellow at JSC; and scientists at the University of Chicago have analyzed drops of water extracted from several meteorites believed to have come from Mars and have concluded that the oxygen isotopes in the water were extraterrestrial.
"It's really a beautiful piece of scientific work to do this analysis," Gibson said. "We are extremely pleased with the results of this team effort." The results of the team's findings are being published in today's issue of the journal SCIENCE.
Photographs returned to Earth from the Mariner 9 and Viking spacecraft show features that suggest Mars once may have had a water-rich atmosphere and flowing water on its surface. Sometime in its history, however, most of the water apparently disappeared, leaving only minute amounts of vapor in the atmosphere.
Through the years, several meteorites have been collected on Earth that scientists have identified as Martian by comparing them to information gleaned by the Viking spacecraft. Six of these meteorites were used in the water extraction procedure.
Gibson said the meteorites were heated in steps in a small vacuum system at JSC to extract trace amounts of water. The water samples were hand-carried to the University of Chicago for analysis of oxygen isotopes. Although the water droplets were less than 1/64ths of an inch in diameter, it was enough to do the analysis.
The analysis determined that the oxygen isotopes in the water were different from the oxygen isotopes in the silicate portion of the meteorites. In other words, the water had a different parent source than the oxygen in the silicate minerals in the meteorites. That parent source could have been the Martian atmosphere, an ancient Martian ocean or even a comet that impacted the planet, Gibson said.
The lack of homogeneous oxygen isotopes on Mars supports the theory that Mars does not have plate tectonics. If such a process had been active on Mars, the oxygen isotopes would have been homogenized as they are on Earth.
Findings from the work completed by the team may answer some questions about the processes operating in the solar system, but the findings raise other questions -- what happened to the water on Mars and does Earth have the same destiny?
"These are large and difficult questions to comprehend," Gibson said, "but perhaps if we can trace the origins and alterations of planetary atmospheres and oceans, the evolution of our solar system may be better understood."
Besides Gibson and Karlsson, who is now in the Department of Geosciences at Texas Tech University, Lubock, team members included Robert N. Clayton and Toshiko K. Mayeda of the Department of Geophysical Sciences and the Enrico Fermi Institute at the University of Chicago.