An international spacecraft that dove through geysers erupting from the surface of a Saturn moon found organic matter, one of many ingredients that make an environment hospitable to extraterrestrial life, scientists said Wednesday.
The discovery excited mission team members, who say it's a marker for further research into whether the icy satellite Enceladus has such an environment.
The chemical analysis by the unmanned Cassini spacecraft revealed that Enceladus' interior was similar to that of a comet.
While the jet plumes were mostly water vapor, the probe found traces of methane and simple organic compounds, said Hunter Waite of the Southwest Research Institute, who is the principal investigator of one of the spacecraft's instruments.
"We clearly have the organics and are closing in on the question of liquid water in the interior," Waite said.
In 2005, Cassini spied gigantic geysers spewing from fractures known as tiger stripes on the moon's south pole. Scientists theorized that reservoirs of liquid water below the surface were likely supplying the ice and vapor seen in the plumes.
The flyby two weeks ago took Cassini within 30 miles from the surface of Enceladus, the shiniest object in the solar system. During the encounter, the spacecraft barreled through the icy geyser plumes at 32,000 mph and an altitude of 120 miles.
Detailed heat maps of the lunar surface revealed the south pole is warmer than previously thought. Temperature measurements show the region is at least minus 135 degrees Fahrenheit — 63 degrees hotter than previously known.
Cassini scientist John Spencer of the Southwest Research Institute said the high temperatures likely indicate that liquid water may lurk beneath the surface.
Scientists generally agree the presence of water, organic compounds and a stable heat source are needed to support primitive life.
Scientists not involved with the mission said while the discovery of organics is important in the search for extraterrestrial life, the fact that they resemble comet material casts doubt on whether liquid water is present.
"Suppose they had seen complex organics ... That would be interpreted to mean that liquid water was present and that chemical reactions had gone forward toward forming life," said Bruce Jakosky, an astrobiologist at the University of Colorado.
"That we don't see those things suggests that liquid water is not abundant or that energy sources are not present," he said.